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LT1 170/LT1 171/LT1172 100kHz, 5A, 2.5A and 1.25A High Efficiency Switching Regulators
FEATURES
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DESCRIPTIO
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Wide Input Voltage Range: 3V to 60V Low Quiescent Current: 6mA Internal 5A Switch (2.5A for LT1171, 1.25A for LT1172) Shutdown Mode Draws Only 50A Supply Current Very Few External Parts Required Self-Protected Against Overloads Operates in Nearly All Switching Topologies Flyback-Regulated Mode Has Fully Floating Outputs Comes in Standard 5-Pin Packages LT1172 Available in 8-Pin MiniDIP and Surface Mount Packages Can Be Externally Synchronized
The LT(R)1170/LT1171/LT1172 are monolithic high power switching regulators. They can be operated in all standard switching configurations including buck, boost, flyback, forward, inverting and "Cuk." A high current, high efficiency switch is included on the die along with all oscillator, control and protection circuitry. Integration of all functions allows the LT1170/LT1171/LT1172 to be built in a standard 5-pin TO-3 or TO-220 power package as well as the 8-pin packages (LT1172). This makes them extremely easy to use and provides "bust proof" operation similar to that obtained with 3-pin linear regulators. The LT1170/LT1171/LT1172 operate with supply voltages from 3V to 60V, and draw only 6mA quiescent current. They can deliver load power up to 100W with no external power devices. By utilizing current-mode switching techniques, they provide excellent AC and DC load and line regulation. The LT1170/LT1171/LT1172 have many unique features not found even on the vastly more difficult to use low power control chips presently available. They use adaptive antisat switch drive to allow very wide ranging load currents with no loss in efficiency. An externally activated shutdown mode reduces total supply current to 50A typically for standby operation.
, LTC and LT are registered trademarks of Linear Technology Corporation. SwitcherCAD is a trademark of Linear Technology Corporation.
APPLICATIO S
s s s s s
Logic Supply 5V at 10A 5V Logic to 15V Op Amp Supply Battery Upconverter Power Inverter (+ to -) or (- to +) Fully Floating Multiple Outputs
USER NOTE: This data sheet is only intended to provide specifications, graphs, and a general functional description of the LT1170/LT1171/LT1172. Application circuits are included to show the capability of the LT1170/LT1171/LT1172. A complete design manual (AN19) should be obtained to assist in developing new designs. This manual contains a comprehensive discussion of both the LT1070 and the external components used with it, as well as complete formulas for calculating the values of these components. The manual can also be used for the LT1170/LT1171/LT1172 by factoring in the higher frequency. A CAD design program called SwitcherCADTM is also available.
TYPICAL APPLICATIO
5V L1** 50H
Boost Converter (5V to 12V) Maximum Output Power*
L2 10H C3 100F
POWER (W) **
OUTPUT FILTER
100 LT1170
VIN VSW
D1 MBR330
80
+
+
LT1170 C3* 100F GND VC R3 1k C1 1F *REQUIRED IF INPUT LEADS 2" FB
C2 1000F
R1 10.7k 1%
12V 1A
60 BOOST
40
R2 1.24k 1%
20 BUCK-BOOST VO = 5V 0 0 10 30 20 INPUT VOLTAGE (V) 40 50
** COILTRONICS 50-2-52 PULSE ENGINEERING 92114
1170/1/2 TA01
U
BUCK-BOOST VO = 30V FLYBACK * ROUGH GUIDE ONLY. BUCK MODE POUT = (5A)(VOUT) SPECIAL TOPOLOGIES DELIVER MORE POWER. ** DIVIDE VERTICAL POWER SCALE BY TWO FOR LT1171, BY FOUR FOR LT1172.
LT1170/1/2 TA02
U
U
1
LT1 170/LT1 171/LT1172
ABSOLUTE
AXI U
RATI GS
Supply Voltage LT1170/71/72HV (Note 2) .................................. 60V LT1170/71/72 (Note 2) ....................................... 40V Switch Output Voltage LT1170/71/72HV ................................................ 75V LT1170/71/72 ..................................................... 65V LT1172S8 ........................................................... 60V Feedback Pin Voltage (Transient, 1ms) ................ 15V Storage Temperature Range ............... - 65C to 150C Lead Temperature (Soldering, 10 sec)................. 300C
PACKAGE/ORDER I FOR ATIO
TOP VIEW GND 1 VC 2 FB 3 NC* 4 J8 PACKAGE 8-LEAD CERDIP 8 7 6 5 E2 VSW E1 VIN
ORDER PART NUMBER LT1172MJ8 LT1172CJ8 LT1172CN8 LT1172IN8 LT1172CS8 LT1172IS8 S8 PART MARKING 1172 1172I ORDER PART NUMBER LT1170MK LT1170CK LT1171MK LT1171CK LT1172MK LT1172CK
N8 PACKAGE 8-LEAD PDIP
S8 PACKAGE 8-LEAD PLASTIC SO
* Do not connect Pin 4 of the LT1172 DIP or SO to external circuitry. This pin may be active in future revisions. TJMAX = 150C, JA = 100C/W (J) TJMAX = 100C, JA = 100C/W (N) TJMAX = 100C, JA = 120C/W to 150C/W depending on board layout (S)
BOTTOM VIEW VSW 1 4 VIN K PACKAGE 4-LEAD TO-3 METAL CAN 2 3 VC CASE IS GND FB
TJMAX JC LT1170MK 150C 2C/W LT1170CK 100C 2C/W LT1171MK 150C 4C/W LT1171CK 100C 4C/W LT1172MK 150C 8C/W LT1172CK 150C 8C/W Based on continuous operation. TJMAX = 125C for intermittent fault conditions. * will vary from approximately 25C/W with 2.8 VIN 5 sq. in. of 1oz. VSW 4 copper to 45C/W GND 3 with 0.20 sq. in. of FB 2 1oz. copper. VC 1 Somewhat lower Q PACKAGE values can be 5-LEAD DD obtained with TJMAX = 100C, JA = *C/W additional copper layers in multilayer boards.
FRONT VIEW
JA 35C/W 35C/W 35C/W 35C/W 35C/W 35C/W
ORDER PART NUMBER LT1170CQ LT1171HVCQ LT1170IQ LT1172CQ LT1171CQ LT1172HVIQ LT1171IQ
2
U
U
W
WW U
W
(Note 1)
Operating Junction Temperature Range LT1170/71/72M ......................... - 55C to 150C LT1170/71/72HVC, LT1170/71/72C (Oper.) .............. 0C to 100C LT1170/71/72HVC C LT1170/71/72C (Sh. Ckt.) .......... 0C to 125C LT1170/71/72HVI, LT1170/71/72I (Oper.) .......... - 40C to 100C LT1170/71/72HVI, I LT1170/71/72I (Sh. Ckt.) ...... - 40C to 125C
TOP VIEW NC 1 NC 2 GND 3 VC 4 FB 5 NC 6 NC 7 NC 8 16 NC 15 NC 14 E2 13 VSW 12 E1 11 VIN 10 NC 9 NC
ORDER PART NUMBER LT1172CSW
SW PACKAGE 16-LEAD PLASTIC SO WIDE
TJMAX = 100C, JA = 150C/W Based on continuous operation. TJMAX = 125C for intermittent fault conditions.
FRONT VIEW 5 4 3 2 1 T PACKAGE 5-LEAD PLASTIC TO-220 VIN VSW GND FB VC
ORDER PART NUMBER LT1170CT LT1170IT LT1170HVCT LT1170HVIT LT1171CT LT1171IT LT1171HVCT LT1172CT LT1172HVCT
TJMAX JC JA LT1170CT/LT1170HVCT 100C 2C/W 75C/W LT1171CT/LT1171HVCT 100C 4C/W 75C/W LT1172CT/LT1172HVCT 100C 8C/W 75C/W Based on continuous operation. TJMAX = 125C for intermittent fault conditions.
LT1 170/LT1 171/LT1172
The q denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. VIN = 15V, VC = 0.5V, VFB = VREF, output pin open, unless otherwise noted.
SYMBOL PARAMETER VREF IB gm Reference Voltage Feedback Input Current Error Amplifier Transconductance Error Amplifier Source or Sink Current Error Amplifier Clamp Voltage Reference Voltage Line Regulation AV IQ Error Amplifier Voltage Gain Minimum Input Voltage (Note 5) Supply Current Control Pin Threshold Normal/Flyback Threshold on Feedback Pin VFB Flyback Reference Voltage (Note 5) Change in Flyback Reference Voltage Flyback Reference Voltage Line Regulation (Note 5) Flyback Amplifier Transconductance (gm) Flyback Amplifier Source and Sink Current BV Output Switch Breakdown Voltage Output Switch "On" Resistance (Note 3) Control Voltage to Switch Current Transconductance ILIM Switch Current Limit (LT1170) IFB = 50A
q
ELECTRICAL CHARACTERISTICS
CONDITIONS
MIN
q q
TYP 1.244 1.244 350
MAX 1.264 1.274 750 1100 6000 7000 350 400 2.30 0.52 0.03
UNITS V V nA nA mho mho A A V V %/V V/V
Measured at Feedback Pin VC = 0.8V VFB = VREF IC = 25A
1.224 1.214
q
3000 2400 150 120 1.80 0.25
4400 200
VC = 1.5V
q
Hi Clamp, VFB = 1V Lo Clamp, VFB = 1.5V 3V VIN VMAX VC = 0.8V 0.9V VC 1.4V
q q
0.38
500
800 2.6 6 3.0 9 1.08 1.25 0.54 17.6 18.0 9 0.03 650 70 70
V mA V V V V V V %/V mho A A V V V
3V VIN VMAX, VC = 0.6V Duty Cycle = 0
q
0.8 0.6 0.4 15.0 14.0 4.5
0.9 0.45 16.3 6.8 0.01
0.05 IFB 1mA IFB = 50A 7V VIN VMAX IC = 10A VC = 0.6V IFB = 50A 3V VIN VMAX, ISW = 1.5mA LT1170 LT1171 LT1172 LT1170 LT1171 LT1172 Duty Cycle = 50% Duty Cycle = 50% Duty Cycle = 80% (Note 4) Duty Cycle = 50% Duty Cycle = 50% Duty Cycle = 80% (Note 4) Duty Cycle = 50% Duty Cycle = 50% Duty Cycle = 80% (Note 4) TJ 25C TJ < 25C TJ 25C TJ < 25C TJ 25C TJ < 25C
q q q q q q q q q
150 Source Sink LT1170/LT1171/LT1172 LT1170HV/LT1171HV/LT1172HV LT1172S8
q q q q q q q q
300 32 40 90 90 80 0.15 0.30 0.60 8 4 2
15 25 65 75 60
VSAT
0.24 0.50 1.00
A/V A/V A/V
5 5 4 2.5 2.5 2.0 1.25 1.25 1.00
10 11 10 5.0 5.5 5.0 3.0 3.5 2.5
A A A A A A A A A
(LT1171)
(LT1172)
3
LT1 170/LT1 171/LT1172
The q denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. VIN = 15V, VC = 0.5V, VFB = VREF, output pin open, unless otherwise noted.
SYMBOL PARAMETER IIN Supply Current Increase During Switch On-Time ISW f DCMAX Switching Frequency
q
ELECTRICAL CHARACTERISTICS
CONDITIONS
MIN
TYP 25
MAX 35 112 115 97 250 250 300
UNITS mA/A kHz kHz % A mV mV s
88 85 85
100 92 100
Maximum Switch Duty Cycle Shutdown Mode Supply Current Shutdown Mode Threshold Voltage Flyback Sense Delay Time (Note 5) 3V VIN VMAX VC = 0.05V 3V VIN VMAX
q
q
100 50
150 1.5
Note 1: Absolute Maximum Ratings are those values beyond which the life of the device may be impaired. Note 2: Minimum effective switch "on" time for the LT1170/71/72 (in current limit only) is 0.6s. This limits the maximum safe input voltage during an output shorted condition. Buck mode and inverting mode input voltage during an output shorted condition is limited to: (R)(IL) + Vf VIN (max, output shorted) = 15V + (t)(f) buck and inverting mode R = Inductor DC resistance IL = 10A for LT1170, 5A for LT1171, and 2.5A for LT1172 Vf = Output catch diode forward voltage at IL t = 0.6s, f = 100kHz switching frequency Maximum input voltage can be increased by increasing R or Vf. External current limiting such as that shown in AN19, Figure 39, will provide protection up to the full supply voltage rating. C1 in Figure 39 should be reduced to 200pF.
Transformer designs will tolerate much higher input voltages because leakage inductance limits rate of rise of current in the switch. These designs must be evaluated individually to assure that current limit is well controlled up to maximum input voltage. Boost mode designs are never protected against output shorts because the external catch diode and inductor connect input to output. Note 3: Measured with VC in hi clamp, VFB = 0.8V. ISW = 4A for LT1170, 2A for LT1171, and 1A for LT1172. Note 4: For duty cycles (DC) between 50% and 80%, minimum guaranteed switch current is given by ILIM = 3.33 (2 - DC) for the LT1170, ILIM = 1.67 (2 - DC) for the LT1171, and ILIM = 0.833 (2 - DC) for the LT1172. Note 5: Minimum input voltage for isolated flyback mode is 7V. VMAX = 55V for HV grade in fully isolated mode to avoid switch breakdown.
TYPICAL PERFOR A CE CHARACTERISTICS
Switch Current Limit vs Duty Cycle*
16
2.9
SWITCH SATURATION VOLTAGE (V)
SWITCH CURRENT (A)
12 25C
MINIMUM INPUT VOLTAGE (V)
8
-55C 125C
4 * DIVIDE VERTICAL SCALE BY TWO FOR LT1171, BY FOUR FOR LT1172. 0 0 10 20 30 40 50 60 70 80 90 100 DUTY CYCLE (%)
1170/1/2 G01
4
UW
Minimum Input Voltage
1.6
SWITCH CURRENT = IMAX 2.8 2.7 2.6 SWITCH CURRENT = 0A 2.5 2.4 2.3 -75 -50 -25
Switch Saturation Voltage
1.4 150C 1.2 1.0 0.8 0.6 0.4 0.2 0 0 1 * DIVIDE CURRENT BY TWO FOR LT1171, BY FOUR FOR LT1172. 2 4 5 6 3 SWITCH CURRENT (A)* 7 8 25C -55C 100C
0 25 50 75 100 125 150 TEMPERATURE (C)
1170/1/2 G02
1170/1/2 G03
LT1 170/LT1 171/LT1172 TYPICAL PERFOR A CE CHARACTERISTICS
Line Regulation
5 1.250
REFERENCE VOLTAGE CHANGE (mV)
4
REFERENCE VOLTAGE (V)
3 2 1 0 -1 -2 -3 -4 -5 0 10 TJ = -55C
TJ = 150C
FEEDBACK BIAS CURRENT (nA)
TJ = 25C
30 40 20 INPUT VOLTAGE (V)
Supply Current vs Supply Voltage (Shutdown Mode)
160 TJ = 25C 140
SUPPLY CURRENT (mA)
SUPPLY CURRENT (A)
DRIVER CURRENT (mA)
120 100 80 60 40 20 0 0 10 30 20 40 SUPPLY VOLTAGE (V) 50 60 VC = 0V VC = 50mV
Shutdown Mode Supply Current
200 180 160
TRANSCONDUCTANCE (mho)
SUPPLY CURRENT (A)
VC PIN CURRENT (A)
140 120 100 80 60 40 20 0 0 10 20 30 40 50 60 70 80 90 100 VC PIN VOLTAGE (mV)
1170/1/2 G10
TJ = 150C
-55C TJ 125C
UW
50
1170/1/2 G04
1170/1/2 G07
Reference Voltage vs Temperature
800 700 600 500 400 300 200 100 1.248 1.246 1.244 1.242 1.240 1.238 1.236 1.234 -75 -50 -25
Feedback Bias Current vs Temperature
60
25 50 75 100 125 150 TEMPERATURE (C) 0
1170/1/2 G05
0 -75 -50 -25
0 25 50 75 100 125 150 TEMPERATURE (C)
1170/1/2 G06
Driver Current* vs Switch Current
160 140 120 100 80 60 40 20 0 0 1 2 3 SWITCH CURRENT (A) 4 5
1170/1/2 G08
Supply Current vs Input Voltage*
15 14 13 12 11 10 9 8 7 6 5 0 10 30 40 20 INPUT VOLTAGE (V) 50 60
1170/1/2 G09
TJ = 25C NOTE THAT THIS CURRENT DOES NOT INCLUDE DRIVER CURRENT, WHICH IS A FUNCTION OF LOAD CURRENT AND DUTY CYCLE. 90% DUTY CYCLE 50% DUTY CYCLE 10% DUTY CYCLE 0% DUTY CYCLE
TJ = -55C
TJ = 25C
* AVERAGE LT1170 POWER SUPPLY CURRENT IS FOUND BY MULTIPLYING DRIVER CURRENT BY DUTY CYCLE, THEN ADDING QUIESCENT CURRENT.
* UNDER VERY LOW OUTPUT CURRENT CONDITIONS, DUTY CYCLE FOR MOST CIRCUITS WILL APPROACH 10% OR LESS.
Error Amplifier Transconductance
5000 4500 4000 3500 3000 2500 2000 1500 1000 500 0 -75 -50 -25 0 25 50 75 100 125 150 TEMPERATURE (C)
1170/1/2 G11
VC Pin Characteristics
300 200 100 0 TJ = 25C -100 -200 VFB = 0.8V (CURRENT OUT OF VC PIN) -300 -400 0 0.5 1.5 2.0 1.0 VC PIN VOLTAGE (V) 2.5 VFB = 1.5V (CURRENT INTO VC PIN)
gm =
I (VC PIN) V (FB PIN)
1170/1/2 G12
5
LT1 170/LT1 171/LT1172 TYPICAL PERFOR A CE CHARACTERISTICS
Idle Supply Current vs Temperature
11 10
IDLE SUPPLY CURRENT (mA)
VC = 0.6V
FEEDBACK VOLTAGE (mV)
9 8 7 6 5 4 3 2 1 -75 -50 -25 0 25 50 75 100 125 150 TEMPERATURE (C)
1170/1/2 G13
SWITCH CURRENT (A)
VSUPPLY = 60V VSUPPLY = 3V
Shutdown Thresholds
400 350 CURRENT (OUT OF VC PIN) - 400 - 350 - 300 - 250 - 200 VOLTAGE 150 100 50 VC VOLTAGE IS REDUCED UNTIL REGULATOR CURRENT DROPS BELOW 300A 0 - 150 -100 - 50
TIME (s)
250 200
1.8 1.6 1.4 1.2 1.0 -75 -50 -25 0 25 50 75 100 125 150 JUNCTION TEMPERATURE (C)
1170/1/2 G17
FLYBACK VOLTAGE (V)
VC PIN VOLTAGE (mV)
300
0 -75 -50 -25
0 25 50 75 100 125 150 TEMPERATURE (C)
1170/1/2 G16
Transconductance of Error Amplifier
7000 6000 -30 0 30 gm 60 90 120 150 180 1k 10k 1M 100k FREQUENCY (Hz) 210 10M
1170/1/2 G19
TRANSCONDUCTANCE (mho)
5000 4000 3000 2000 1000 0
FEEDBACK PIN VOLTAGE (mV)
-1000
6
UW
Feedback Pin Clamp Voltage
500 450 400 350 300 250 200 150 100 50 0 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 FEEDBACK CURRENT (mA)
1170/1/2 G14
Switch "Off" Characteristics
1000 900 800
-55C 25C 150C
700 600 500 VSUPPLY = 3V 400 300 200 100 0 0 VSUPPLY = 15V
VSUPPLY = 40V
VSUPPLY = 55V
10 20 30 40 50 60 70 80 90 100 SWITCH VOLTAGE (V)
1170/1/2 G15
Flyback Blanking Time
2.2 2.0
VC PIN CURRENT (A)
Isolated Mode Flyback Reference Voltage
23 22 21 20 19 18 17 16 15 -75 -50 -25 RFB = 10k RFB = 1k RFB = 500
0 25 50 75 100 125 150 TEMPERATURE (C)
1170/1/2 G18
Normal/Flyback Mode Threshold on Feedback Pin
500 490 480 470 460 450 440 430 420 410 400 -50 -25 0 FEEDBACK PIN CURRENT (AT THRESHOLD) FEEDBACK PIN VOLTAGE (AT THRESHOLD) -24 -22 FEEDBACK PIN CURRENT (A) -20 -18 -16 -14 -12 -10 -8 -6 -4 25 50 75 100 125 150 TEMPERATURE (C)
1170/1/2 G20
PHASE (DEG)
LT1 170/LT1 171/LT1172
BLOCK DIAGRA
FB
ALWAYS CONNECT E1 TO THE GROUND PIN ON MINIDIP, 8- AND 16-PIN SURFACE MOUNT PACKAGES.
E1 AND E2 INTERNALLY TIED TO GROUND ON TO-3 AND TO-220 PACKAGES.
OPERATIO
The LT1170/LT1171/LT1172 are current mode switchers. This means that switch duty cycle is directly controlled by switch current rather than by output voltage. Referring to the block diagram, the switch is turned "on" at the start of each oscillator cycle. It is turned "off" when switch current reaches a predetermined level. Control of output voltage is obtained by using the output of a voltage sensing error amplifier to set current trip level. This technique has several advantages. First, it has immediate response to input voltage variations, unlike ordinary switchers which have notoriously poor line transient response. Second, it reduces the 90 phase shift at midfrequencies in the energy storage inductor. This greatly simplifies closedloop frequency compensation under widely varying input voltage or output load conditions. Finally, it allows simple pulse-by-pulse current limiting to provide maximum switch
W
VIN 16V SWITCH OUT 2.3V REG FLYBACK ERROR AMP 5A, 75V SWITCH 100kHz OSC LOGIC DRIVER LT1172 MODE SELECT COMP ANTISAT
- +
ERROR AMP VC
+
SHUTDOWN CIRCUIT 1.24V REF CURRENT AMP GAIN 6 0.15V (LT1170 AND LT1171 ONLY)
-
0.02 (0.04 LT1171) (0.16 LT1172)
0.16
E1
E2
1170/1/2 BD
U
protection under output overload or short conditions. A low dropout internal regulator provides a 2.3V supply for all internal circuitry on the LT1170/LT1171/LT1172. This low dropout design allows input voltage to vary from 3V to 60V with virtually no change in device performance. A 100kHz oscillator is the basic clock for all internal timing. It turns "on" the output switch via the logic and driver circuitry. Special adaptive anti-sat circuitry detects onset of saturation in the power switch and adjusts driver current instantaneously to limit switch saturation. This minimizes driver dissipation and provides very rapid turnoff of the switch. A 1.2V bandgap reference biases the positive input of the error amplifier. The negative input is brought out for output voltage sensing. This feedback pin has a second
7
LT1 170/LT1 171/LT1172
OPERATIO
function; when pulled low with an external resistor, it programs the LT1170/LT1171/LT1172 to disconnect the main error amplifier output and connects the output of the flyback amplifier to the comparator input. The LT1170/ LT1171/LT1172 will then regulate the value of the flyback pulse with respect to the supply voltage.* This flyback pulse is directly proportional to output voltage in the traditional transformer coupled flyback topology regulator. By regulating the amplitude of the flyback pulse, the output voltage can be regulated with no direct connection between input and output. The output is fully floating up to the breakdown voltage of the transformer windings. Multiple floating outputs are easily obtained with additional windings. A special delay network inside the LT1170/ LT1171/LT1172 ignores the leakage inductance spike at the leading edge of the flyback pulse to improve output regulation. The error signal developed at the comparator input is brought out externally. This pin (VC) has four different functions. It is used for frequency compensation, current limit adjustment, soft starting, and total regulator shutdown. During normal regulator operation this pin sits at a voltage between 0.9V (low output current) and 2.0V (high output current). The error amplifiers are current output (gm) types, so this voltage can be externally clamped for adjusting current limit. Likewise, a capacitor coupled external clamp will provide soft start. Switch duty cycle goes to zero if the VC pin is pulled to ground through a diode, placing the LT1170/LT1171/LT1172 in an idle mode. Pulling the VC pin below 0.15V causes total regulator shutdown, with only 50A supply current for shutdown circuitry biasing. See AN19 for full application details. Extra Pins on the MiniDIP and Surface Mount Packages The 8- and 16-pin versions of the LT1172 have the emitters of the power transistor brought out separately from the ground pin. This eliminates errors due to ground pin voltage drops and allows the user to reduce switch current limit 2:1 by leaving the second emitter (E2) disconnected. The first emitter (E1) should always be connected to the ground pin. Note that switch "on" resistance doubles when E2 is left open, so efficiency will suffer somewhat
*See note under block diagram.
8
U
when switch currents exceed 300mA. Also, note that chip dissipation will actually increase with E2 open during normal load operation, even though dissipation in current limit mode will decrease. See "Thermal Considerations" next. Thermal Considerations When Using the MiniDIP and SW Packages The low supply current and high switch efficiency of the LT1172 allow it to be used without a heat sink in most applications when the TO-220 or TO-3 package is selected. These packages are rated at 50C/W and 35C/W respectively. The miniDIPs, however, are rated at 100C/W in ceramic (J) and 130C/W in plastic (N). Care should be taken for miniDIP applications to ensure that the worst case input voltage and load current conditions do not cause excessive die temperatures. The following formulas can be used as a rough guide to calculate LT1172 power dissipation. For more details, the reader is referred to Application Note 19 (AN19), "Efficiency Calculations" section. Average supply current (including driver current) is: IIN 6mA + ISW (0.004 + DC/40) ISW = switch current DC = switch duty cycle Switch power dissipation is given by: PSW = (ISW)2 * (RSW)(DC) RSW = LT1172 switch "on" resistance (1 maximum) Total power dissipation is the sum of supply current times input voltage plus switch power: PD(TOT) = (IIN)(VIN) + PSW In a typical example, using a boost converter to generate 12V at 0.12A from a 5V input, duty cycle is approximately 60%, and switch current is about 0.65A, yielding: IIN = 6mA + 0.65(0.004 + DC/40) = 18mA PSW = (0.65)2 * (1)(0.6) = 0.25W PD(TOT) = (5V)(0.018A) + 0.25 = 0.34W
LT1 170/LT1 171/LT1172
OPERATIO
Temperature rise in a plastic miniDIP would be 130C/W times 0.34W, or approximately 44C. The maximum ambient temperature would be limited to 100C (commercial temperature limit) minus 44C, or 56C. In most applications, full load current is used to calculate die temperature. However, if overload conditions must also be accounted for, four approaches are possible. First, if loss of regulated output is acceptable under overload conditions, the internal thermal limit of the LT1172 will protect the die in most applications by shutting off switch current. Thermal limit is not a tested parameter, however, and should be considered only for noncritical applications with temporary overloads. A second approach is to use the larger TO-220 (T) or TO-3 (K) package which, even without a heat sink, may limit die temperatures to safe levels under overload conditions. In critical situations, heat sinking of these packages is required; especially if overload conditions must be tolerated for extended periods of time. The third approach for lower current applications is to leave the second switch emitter (miniDIP only) open. This increases switch "on" resistance by 2:1, but reduces switch current limit by 2:1 also, resulting in a net 2:1 reduction in I2R switch dissipation under current limit conditions. The fourth approach is to clamp the VC pin to a voltage less than its internal clamp level of 2V. The LT1172 switch current limit is zero at approximately 1V on the VC pin and 2A at 2V on the VC pin. Peak switch current can be externally clamped between these two levels with a diode. See AN19 for details.
Synchronizing with Bipolar Transistor
VIN
LT1170
GND
U
LT1170/LT1171/LT1172 Synchronizing The LT1170/LT1171/LT1172 can be externally synchronized in the frequency range of 120kHz to 160kHz. This is accomplished as shown in the accompanying figures. Synchronizing occurs when the VC pin is pulled to ground with an external transistor. To avoid disturbing the DC characteristics of the internal error amplifier, the width of the synchronizing pulse should be under 0.3s. C2 sets the pulse width at 0.2s. The effect of a synchronizing pulse on the LT1170/LT1171/LT1172 amplifier offset can be calculated from: KT V tS fS IC + C q R3 VOS = IC KT = 26mV at 25C q tS = pulse width fS = pulse frequency IC = VC source current ( 200A) VC = operating VC voltage (1V to 2V) R3 = resistor used to set mid-frequency "zero" in frequency compensation network.
( )( )
With tS = 0.2s, fS = 150kHz, VC = 1.5V, and R3 = 2k, offset voltage shift is 3.8mV. This is not particularly bothersome, but note that high offsets could result if R3 were reduced to a much lower value. Also, the synchronizing transistor must sink higher currents with low values of R3, so larger drives may have to be used. The transistor must be capable of pulling the VC pin to within 200mV of ground to ensure synchronizing.
Synchronizing with MOS Transistor
VIN
LT1170
VC C2 39pF R3 C1 2N2369 R2 2.2k FROM 5V LOGIC
1170/1/2 OP01
GND
VC D1 1N4158 VN2222* R2 2.2k * SILICONIX OR EQUIVALENT D2 1N4158 FROM 5V LOGIC
1170/1/2 OP02
R1 3k
C2 100pF
R3 C1
9
LT1 170/LT1 171/LT1172
TYPICAL APPLICATIO S
Flyback Converter
VIN 20V TO 30V
VIN C4* 100F
D2 MUR110 VSW
+
LT1170
FB GND VC R3 1.5k C2 0.15F *REQUIRED IF INPUT LEADS 2" R2 1.24k 0 IPRI 0 IPRI
E2 LT1172 E1 GND VC
OPTIONAL SHUTDOWN
VN2222
C4 0.047F
D2, D3 = ER82.004 600mA SCHOTTKY. OTHER FAST SWITCHING TYPES MAY BE USED. * VIN AND BATTERY MAY BE TIED TOGETHER. MAXIMUM VALUE FOR VBAT IS EQUAL TO THE NEGATIVE OUTPUT + 1V. WITH HIGHER BATTERY VOLTAGES, HIGHEST EFFICIENCY IS OBTAINED BY RUNNING THE LT1172 VIN PIN FROM 5V. SHUTTING OFF THE 5V SUPPLY WILL AUTOMATICALLY TURN OFF THE LT1172. EFFICIENCY IS ABOUT 80% AT IOUT = 25mA. R1, R2, R3 ARE MADE LARGE TO MINIMIZE BATTERY DRAIN IN SHUTDOWN, WHICH IS APPROXIMATELY VBAT /(R1 + R2 + R3). ** FOR HIGH EFFICIENCY, L1 SHOULD BE MADE ON A FERRITE OR MOLYPERMALLOY CORE. PEAK INDUCTOR CURRENTS ARE ABOUT 600mA AT POUT = 0.7. INDUCTOR SERIES RESISTANCE SHOULD BE LESS THAN 0.4 FOR HIGH EFFICIENCY. *** OUTPUT RIPPLE IS ABOUT 200mVP-P TO 400mVP-P WITH C2 = 2F TANTALUM. IF LOWER RIPPLE IS DESIRED, INCREASE C2, OR ADD A 10 , 1F TANTALUM OUTPUT FILTER. 1170/1/2 TA04
10
+
U
L2 OPTIONAL FILTER 5H C4 100F VIN N* = 1/3 D3 25V 1W 1 N* D1 VOUT 5V 6A
VSNUB
CLAMP TURN-ON SPIKE
a b 0V c VOUT + Vf N * VIN d R1 3.74k 0 IPRI/N I IPRI
+ Vf V PRIMARY FLYBACK VOLTAGE = OUT N LT1170 SWITCH VOLTAGE AREA "a" = AREA "b" TO MAINTAIN ZERO DC VOLTS ACROSS PRIMARY SECONDARY VOLTAGE AREA "c" = AREA "d" TO MAINTAIN ZERO DC VOLTS ACROSS SECONDARY
+
C1 2000F
0V
PRIMARY CURRENT
SECONDARY CURRENT
LT1170 SWITCH CURRENT
SNUBBER DIODE CURRENT 0 (I )(L ) t = PRI L VSNUB
1170/1/2 TA03
LCD Contrast Supply
5V* VIN VSW
L1** 50H
VBAT* 3V TO 20V
+
R2 100k R1 200k D1 1N914
C1 1F TANTALUM VOUT -10V TO -26V D2
FB
R3 15k
C3 0.0047F
D3
C2*** 2F TANTALUM
LT1 170/LT1 171/LT1172
TYPICAL APPLICATIO S
Driving High Voltage FET (for Off-Line Applications, See AN25)
G VIN D1 VSW D Q1
10V TO 20V
+
LT1170
GND
1170/1/2 TA05
Negative-to-Positive Buck-Boost Converter
L1** 50H
VIN
C4* 100F
+
LT1170 FB R3 2.2k C1 0.22F R2 1.24k
OPTIONAL INPUT FILTER L3
GND
VIN -20V
* REQUIRED IF INPUT LEADS 2" ** PULSE ENGINEERING 92114, COILTRONICS 50-2-52 THIS CIRCUIT IS OFTEN USED TO CONVERT -48V TO 5V. TO GUARANTEE FULL SHORT-CIRCUIT PROTECTION, THE CURRENT LIMIT CIRCUIT SHOWN IN AN19, FIGURE 39, SHOULD BE ADDED WITH C1 REDUCED TO 200pF.
* REQUIRED IF INPUT LEADS 2" ** PULSE ENGINEERING 92114 COILTRONICS 50-2-52
C3* 100F
+
LT1170 FB GND VC C1 R3 R2 1.24k Q1 2N3906
OPTIONAL INPUT FILTER L3
VIN -20V
U
VC
(Note that maximum output currents are divided by 2 for LT1171, by 4 for LT1172.)
External Current Limit
VX LT1170 R2
2V
R1 500 D1
GND
VC
1170/1/2 TA06
External Current Limit
L2 OPTIONAL OUTPUT FILTER
D1
VIN
VSW
C3
+
VSW
LT1170 VIN GND R1 1k Q1 C1 1000pF RS C2 VC FB
+
C2 1000F Q1
R1 11.3k
VOUT 12V 2A
-
R2
NOTE THAT THE LT1170 GND PIN IS NO LONGER COMMON TO VIN-.
1170/1/2 TA08
1170/1/2 TA07
Negative Buck Converter +
D1 VIN VSW L1** 50H
C2 1000F
R1 4.64k R4 12k
LOAD -5.2V 4.5A
OPTIONAL OUTPUT FILTER L2 4H
+
C4 200F
1170/1/2 TA09
11
LT1 170/LT1 171/LT1172
TYPICAL APPLICATIO S
Positive-to-Negative Buck-Boost Converter
D3 1N4001 R5 470, 1W VIN 10V TO 30V
VIN
C4 1F
+
LT1170 R1 10.7k GND VC FB R3 5k C2 0.1F R2 1.24k D2 1N914 R4 47
INPUT VOLTAGE > VBAT + 2V < 35V D1 1N5819
C1 + 200F 35V
C2 2.2F 35V TANTALUM
+
RUN = 0V SHUTDOWN = 5V
INPUT VOLTAGE 4.5V TO 20V 1k 1N5818 L1** 300H Q1* E2 10F TANT V IN VSW
+
LT1172
E1 GND
2F
12
U
R6 78k
+
VSW
C5 100F*
* REQUIRED IF INPUT LEADS 2" ** PULSE ENGINEERING 92114, COILTRONICS 50-2-52 TO AVOID STARTUP PROBLEMS FOR INPUT VOLTAGES BELOW 10V, CONNECT ANODE OF D3 TO VIN, AND REMOVE R5. C1 MAY BE REDUCED FOR LOWER OUTPUT CURRENTS. C1 (500F)(IOUT). FOR 5V OUTPUTS, REDUCE R3 TO 1.5k, INCREASE C2 TO 0.3F, AND REDUCE R6 TO 100.
+
C3 2F
+
D1
C1 1000F
R6 470
VOUT -12V 2A
L1** 50H
1170/1/2 TA10
High Efficiency Constant Current Charger
R3 25k ICHRG = 1.244V * R4 = 1A AS SHOWN R3 * R5
VSW LT1171 VIN GND FB VC C4 0.01F V
+
R2 1k
- +
R4 1k
* L2 REDUCES RIPPLE CURRENT INTO THE BATTERY BY ABOUT 20 :1. IT MAY BE OMITTED IF DESIRED.
LT1006 V-
+
C3 0.47F
L1 100H, 1A R5 0.05
L2* 10H, 1A
2N3904 R7 22k R8 1k D2 MBR340
+
C4 200F 25V
1A
+
BATTERY 2V TO 25V
1170/1/2 TA11
Backlight CCFL Supply (see AN45 for details)
L2*** 33pF 3kV
A
LAMP
0.02F Q2* B
D1 1N914
D2 1N914
50k INTENSITY ADJUST
R3 10k
R1 560
VC
FB C6 1 F
* Q1,Q2 = BCP56 OR MPS650/561 1170/1/2 TA12 ** COILTRONICS CTX300-4 *** SUMIDA 6345-020 OR COILTRONICS 110092-1 A MODIFICATION WILL ALLOW OPERATION DOWN TO 4.5V. CONSULT FACTORY.
+
LT1 170/LT1 171/LT1172
TYPICAL APPLICATIO S
Positive Buck Converter
VIN D3
C3 2.2F
+
+
C5* 100F GND VC
C4* 470F
+
GND VC
VIN -15V
* REQUIRED IF INPUT LEADS 2"
U
* REQUIRED IF INPUT LEADS 2" ** PULSE ENGINEERING 92114 COILTRONICS 50-2-52
VIN
L2 4H
VSW
LT1170 R1 3.74k FB R3 470 C1 1F D1 R2 1.24k r
D2 1N914
OPTIONAL OUTPUT FILTER
C5 200F
+
C2 1F L1** 50H C4 1000F
R4 10 5V, 4.5A 100mA MINIMUM
1170/1/2 TA13
+
Negative Boost Regulator
D2
VIN VSW LT1170 FB R2 1.24k D1 VOUT -28V, 1A
1170/1/2 TA14
R1 27k
+
C3 10F
+
C1 1000F
RO (MINIMUM LOAD)
L1 50H
R3 3.3k C2 0.22F
Driving High Voltage NPN
C1 D2
R2**
R1* Q1 D1
VIN VSW LT1170
* SETS IB (ON) ** SETS IB (OFF)
GND
1170/1/2 TA15
13
LT1 170/LT1 171/LT1172
TYPICAL APPLICATIO S
Forward Converter
D1 T1 R4 C2 1 M N D2 VIN VSW VIN 20V TO 30V LT1170 FB GND VC Q1 R3 C3 R6 330 R5 1 R2 1.24k D4 D3 C1 2000F
VIN
+
C1 330F 35V C6 0.02F
D1 MBR330p
MODE LOGIC 220pF <0.3V = NORMAL MODE >2.5V = SHUTDOWN OPEN = BURST MODE
14
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L1 25H
VOUT 5V, 6A
+
R1 3.74k
C4
1170/1/2 TA16
High Efficiency 5V Buck Converter
10H 3A 100F 16V
VSW LT1170 FB VC
VIN
+
GND
D2 1N4148
OPTIONAL OUTPUT FILTER
R1 680 C4 0.1F
C5 0.03F
C3 4.7F TANT
+
L1 50H R2* 0.013
+
VC VIN LT1432 MODE GND DIODE V+ VLIM VOUT
x
C2 390F 16V
VOUT 5V 3A**
* R2 IS MADE FROM PC BOARD COPPER TRACES. ** MAXIMUM CURRENT IS DETERMINED BY THE CHOICE OF LT1070 FAMILY. SEE APPLICATION SECTION.
1170/1/2 TA17
LT1 170/LT1 171/LT1172
PACKAGE DESCRIPTIO
CORNER LEADS OPTION (4 PLCS)
0.045 - 0.068 (1.143 - 1.727) FULL LEAD OPTION 0.300 BSC (0.762 BSC)
0.008 - 0.018 (0.203 - 0.457)
NOTE: LEAD DIMENSIONS APPLY TO SOLDER DIP/PLATE OR TIN PLATE LEADS
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Dimensions in inches (millimeters) unless otherwise noted.
J8 Package 8-Lead CERDIP (Narrow 0.300, Hermetic)
(LTC DWG # 05-08-1110)
0.005 (0.127) MIN
0.405 (10.287) MAX 8 7 6 5
0.023 - 0.045 (0.584 - 1.143) HALF LEAD OPTION
0.025 (0.635) RAD TYP 1 2 3
0.220 - 0.310 (5.588 - 7.874)
4
0.200 (5.080) MAX 0.015 - 0.060 (0.381 - 1.524)
0 - 15
0.045 - 0.065 (1.143 - 1.651) 0.014 - 0.026 (0.360 - 0.660) 0.100 (2.54) BSC
0.125 3.175 MIN
J8 1298
15
LT1 170/LT1 171/LT1172
PACKAGE DESCRIPTIO
0.320 - 0.350 (8.13 - 8.89)
0.760 - 0.775 (19.30 - 19.69) 0.060 - 0.135 (1.524 - 3.429)
0.420 - 0.480 (10.67 - 12.19)
0.300 - 0.325 (7.620 - 8.255)
0.009 - 0.015 (0.229 - 0.381)
(
+0.035 0.325 -0.015 8.255 +0.889 -0.381
)
*THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS. MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.010 INCH (0.254mm)
16
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Dimensions in inches (millimeters) unless otherwise noted. K Package 4-Lead TO-3 Metal Can
(LTC DWG # 05-08-1311)
1.177 - 1.197 (29.90 - 30.40) 0.655 - 0.675 (16.64 - 19.05) 0.151 - 0.161 (3.84 - 4.09) DIA 2 PLC 0.167 - 0.177 (4.24 - 4.49) R
0.470 TP P.C.D.
0.038 - 0.043 (0.965 - 1.09) 18
72
0.490 - 0.510 (12.45 - 12.95) R
K4(TO-3) 1098
N8 Package 8-Lead PDIP (Narrow 0.300)
(LTC DWG # 05-08-1510)
0.400* (10.160) MAX 8 7 6 5
0.255 0.015* (6.477 0.381)
1
2
3
4 0.130 0.005 (3.302 0.127)
0.045 - 0.065 (1.143 - 1.651)
0.065 (1.651) TYP 0.125 (3.175) 0.020 MIN (0.508) MIN 0.018 0.003 (0.457 0.076)
N8 1098
0.100 (2.54) BSC
LT1 170/LT1 171/LT1172
PACKAGE DESCRIPTIO
0.256 (6.502)
0.060 (1.524)
0.060 (1.524)
0.183 (4.648)
0.075 (1.905) 0.300 (7.620) BOTTOM VIEW OF DD PAK HATCHED AREA IS SOLDER PLATED COPPER HEAT SINK +0.012 0.143 -0.020 0.067 (1.70) 0.028 - 0.038 BSC (0.711 - 0.965) 0.013 - 0.023 (0.330 - 0.584)
0.010 - 0.020 x 45 (0.254 - 0.508) 0.008 - 0.010 (0.203 - 0.254) 0- 8 TYP
0.014 - 0.019 (0.355 - 0.483) TYP *DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE **DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE
0.016 - 0.050 (0.406 - 1.270)
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Dimensions in inches (millimeters) unless otherwise noted. Q Package 5-Lead Plastic DD Pak
(LTC DWG # 05-08-1461)
0.060 (1.524) TYP
0.390 - 0.415 (9.906 - 10.541) 15 TYP
0.165 - 0.180 (4.191 - 4.572)
0.045 - 0.055 (1.143 - 1.397) +0.008 0.004 -0.004
0.330 - 0.370 (8.382 - 9.398)
0.059 (1.499) TYP
(
+0.203 0.102 -0.102
)
0.095 - 0.115 (2.413 - 2.921) 0.050 0.012 (1.270 0.305)
Q(DD5) 1098
(
+0.305 3.632 -0.508
)
S8 Package 8-Lead Plastic Small Outline (Narrow 0.150)
(LTC DWG # 05-08-1610)
0.189 - 0.197* (4.801 - 5.004) 8 7 6 5
0.228 - 0.244 (5.791 - 6.197)
0.150 - 0.157** (3.810 - 3.988)
1
2
3
4
0.053 - 0.069 (1.346 - 1.752)
0.004 - 0.010 (0.101 - 0.254)
0.050 (1.270) BSC
SO8 1298
17
LT1 170/LT1 171/LT1172
PACKAGE DESCRIPTIO
0.291 - 0.299** (7.391 - 7.595) 0.010 - 0.029 x 45 (0.254 - 0.737) 0 - 8 TYP
0.009 - 0.013 (0.229 - 0.330)
NOTE 1 0.016 - 0.050 (0.406 - 1.270)
NOTE: 1. PIN 1 IDENT, NOTCH ON TOP AND CAVITIES ON THE BOTTOM OF PACKAGES ARE THE MANUFACTURING OPTIONS. THE PART MAY BE SUPPLIED WITH OR WITHOUT ANY OF THE OPTIONS *DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE **DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE
18
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Dimensions in inches (millimeters) unless otherwise noted.
SW Package 16-Lead Plastic Small Outline (Wide 0.300)
(LTC DWG # 05-08-1620)
0.398 - 0.413* (10.109 - 10.490) 16 15 14 13 12 11 10 9
NOTE 1
0.394 - 0.419 (10.007 - 10.643)
1
2
3
4
5
6
7
8
0.093 - 0.104 (2.362 - 2.642)
0.037 - 0.045 (0.940 - 1.143)
0.050 (1.270) BSC
0.004 - 0.012 (0.102 - 0.305)
0.014 - 0.019 (0.356 - 0.482) TYP
S16 (WIDE) 1098
LT1 170/LT1 171/LT1172
PACKAGE DESCRIPTIO
0.390 - 0.415 (9.906 - 10.541)
0.230 - 0.270 (5.842 - 6.858) 0.460 - 0.500 (11.684 - 12.700) 0.570 - 0.620 (14.478 - 15.748) 0.330 - 0.370 (8.382 - 9.398) 0.700 - 0.728 (17.78 - 18.491) 0.620 (15.75) TYP
BSC
0.067 (1.70)
0.028 - 0.038 (0.711 - 0.965)
Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
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Dimensions in inches (millimeters) unless otherwise noted.
T Package 5-Lead Plastic TO-220 (Standard)
(LTC DWG # 05-08-1421)
0.165 - 0.180 (4.191 - 4.572)
0.147 - 0.155 (3.734 - 3.937) DIA
0.045 - 0.055 (1.143 - 1.397)
SEATING PLANE 0.152 - 0.202 0.260 - 0.320 (3.861 - 5.131) (6.60 - 8.13)
0.095 - 0.115 (2.413 - 2.921) 0.155 - 0.195* (3.937 - 4.953) 0.013 - 0.023 (0.330 - 0.584)
0.135 - 0.165 (3.429 - 4.191)
* MEASURED AT THE SEATING PLANE
T5 (TO-220) 0399
19
LT1 170/LT1 171/LT1172
TYPICAL APPLICATIO
VIN 28V
GND
C5* 100F
+
* REQUIRED IF INPUT LEADS 2"
RELATED PARTS
PART NUMBER LT1070/LT1071/LT1072 LT1074/LT1076 LT1082 LT1268/LT1268B LT1269/LT1271 LT1270/LT1270A LT1370 LT1371 LT1372/LT1377 LT1373 LT1374 LT1375/LT1376 LT1425 LT1507 LT1533 DESCRIPTION 5A/2.5A/1.25A High Efficiency Switching Regulators 5.5A/2A Step-Down Switching Regulators 1A, High Voltage, High Efficiency Switching Regulator 7.5A, 150kHz Switching Regulators 4A High Efficiency Switching Regulators 8A and 10A High Efficiency Switching Regulators 500kHz High Efficiency 6A Switching Regulator 500kHz High Efficiency 3A Switching Regulator 500kHz and 1MHz High Efficiency 1.5A Switching Regulators 250kHz Low Supply Current High Efficiency 1.5A Switching Regulator 4A, 500kHz Step-Down Switching Regulator 1.5A, 500kHz Step-Down Switching Regulators Isolated Flyback Switching Regulator 500kHz Monolithic Buck Mode Switching Regulator Ultralow Noise 1A Switching Regulator COMMENTS 40kHz, VIN to 60V, VSW to 75V 100kHz, Also for Positive-to-Negative Conversion VIN to 75V, VSW to 100V, Telecom VIN to 30V, VSW to 60V 100kHz/60kHz, VIN to 30V, VSW to 60V 60kHz, VIN to 30V, VSW to 60V High Power Boost, Flyback, SEPIC Good for Boost, Flyback, Inverting, SEPIC Directly Regulates VOUT Low 1mA Quiescent Current Synchronizable, VIN to 25V Up to 1.25A Out from an SO-8 6W Output, 5% Regulation, No Optocoupler Needed 1.5A Switch, Good for 5V to 3.3V Push-Pull, <100VP-P Output Noise
20
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417 q (408) 432-1900 FAX: (408) 434-0507q TELEX: 499-3977 q www.linear-tech.com
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Positive Current Boosted Buck Converter
470 2W C3 0.47F C6 0.002F 1: N N 0.25 D1 R6 470 VIN VSW LT1170 FB VC R3 680 C1 0.33F C4 0.01F VIN 7 6 4 8 200pF R4 1.24k VOUT 5V, 10A C2 5000F LM308 2 R5 5k R7 1k R2 1.24k D2
- +
3
R1 5k
+
1170/1/2 TA18
117012fe LT/TP 1299 2K REV E * PRINTED IN USA
(c) LINEAR TECHNOLOGY CORPORATION 1991

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