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(R)
Preliminary
SP6659
1.5MHz, 600mA Synchronous Buck Regulator
FEATURES 94% Efficiency Possible 600mA Output Current at VIN = 3V 2.5V to 5.5V Input Voltage Range 1.5MHz constant frequency operation No Schottky Diode Required Output Voltages as low as 0.6V Slope Compensated Current Mode Operation for Excellent Line and Load Transient Response 100 % Duty Cycle in LDO Mode <1A Shutdown Current, Quiescent Current of 300 A Over-temperature protected Offered in Low Profile TSOT-23 package
VFB VIN
VOUT
VIN
5
4
5
4
SP6659
5 Pin TSOT-23
1
RUN
SP6659
5 Pin TSOT-23
1
RUN
2
GND
3
SW
2
GND
3
SW
Adjustable
Fixed
Now Available in Lead Free Packaging
APPLICATIONS Cell Phones Wireless and DSL Modems DSC's Portable Instruments DESCRIPTION
The SP6659 is a 600mA synchronous buck regulator using a constant frequency, current mode architecture. The output voltage can be programmed using an external resistor divider. The 2.5V to 5.5V input voltage range is ideal for portable applications that use a Li-Ion battery. Switching frequency is internally set at 1.5MHz, allowing the use of small surface mount inductors and capacitors. The internal synchronous switch increases efficiency and eliminates the need for an external Schottky diode. The output voltage can be programmed using an external resistor divider. Low output voltages are easily supported with the 0.6V feedback reference voltage. The SP6659 is available in a low profile 5 pin TSOT-23 package. TYPICAL APPLICATION SCHEMATICS
(R)
(R)
2.2H V IN RUN
4 3
2.2H
C2
SW
22pF
V OUT
V IN
4
SP6659
3
SW
V OUT
SP6659
4.7F Ceramic
1 5 2
R2 V FB R1 GND
4.7F 10F Ceramic Ceramic
RUN 1
5 2
V OUT
10F Ceramic
GND
Adjustable
Fixed
Date: 07/20/05
SP6659 1.5MHz, 600mA Synchronous Buck Regulator
(c) Copyright 2005 Sipex Corporation
1
ABSOLUTE MAXIMUM RATINGS
Input Supply Voltage ......................................................... -0.3V to +6V RUN, VFBVoltages .................................................. -0.3V to (VIN + 0.3V) SW Voltage ............................................................ -0.3V to (VIN + 0.3V) P-Channel Switch Source Current ............................................. 800mA N-Channel Switch Sink Current .................................................. 800mA Peak Switch Sink and Source Current ........................................... 1.3A Operating Temperature ................................................. -40C to +85C Storage Temperature ................................................. -65C to +150 C Junction Temperature (Note 1) .................................................. 125 C These are stress ratings only and functional operation of the device at these ratings or any other above those indicated in the operation sections of the specifications below is not implied. Exposure to absolute maximum rating conditions for extended periods of time may affect reliability.
ELECTRICAL CHARACTERISTICS
Vin=Vrun=3.6V, Io=0mA, Tamb= -40C to +85C, typical values at 25C unless otherwise noted.
Parameter
Input Voltage Range Input DC Supply Current Active Mode Shutdown Mode
Min
2.5
Typ
Max
5.5
Units
V
Conditions
300 0.1 0.5880 0.6000 0.6000 0.6000 85 -1 -0.1 1.455 1.746 0.4 0.01 1.500 1.800
400 1 0.6120 0.6135 0.6180 300 1 0.1 1.545 1.854
A A
Vfb = 0.5V, Vin = Vrun Vin = 3.6V, Vrun = ZeroV Ta=+25C
Vfb (Feedback Voltage)
0.5865 0.5820
V
0CVfb Input Bias Current Vfb Line Regulation Vfb Load Regulation Regulated Output Voltage
nA %/V %/mA V V V
Vfb = 1.0V Vin = 2.5V to 5.5V ILoad = 0mA to 600mA SP6659EK1-1.5, -40C < Ta < +85C SP6659EK1-1.8, -40C < Ta < +85C
Minimum Output Voltage Peak inductor current Oscillator frequency P-channel ON resistance N-channel ON resistance SW Leakage Current
0.6 0.7 0.8 1.15 1.4 0.4 0.4 0.01 0.2 1 0.01 1.5 1.8 0.6 0.6 1.0 1.3 1.5
A mHz A V
Vfb = 0.5V Closed Loop, ILoad=100mA ISW = 100mA ISW = -100mA Vrun=ZeroV, Vin = 3.6V Vsw=ZeroV, Vsw = Vin
Run Threshold Voltage Run Leakage Current
A
Note 1: Junction Temperature TJ is calculated from the ambient temperature TA and ower dissipation PD according to the following formula: TJ = TA + PD X 220C/W
PIN DESCRIPTION
PIN # 1 2 3 4 PIN NAME RUN GND SW V IN DESCRIPTION Power down control pin. Forcing this pin above 1.5V enables the device. Forcing this pin below 0.3V shuts down the device. Ground pin. Switching node. Power supply pin Adjustable Version: VFB, Feedback Input Pin. Connect FB to the center point of the external resistor divider. The feedback threshold voltage is 0.6V. 5 VFB/ VOUT Fixed Output Version: VOUT, Output Voltage Feedback Pin. An internal resistive divider drops the output voltage down for comparison to the internal reference voltage.
Date: 07/20/05 SP6659 1.5MHz, 600mA Synchronous Buck Regulator (c) Copyright 2005 Sipex Corporation
2
TYPICAL PERFORMANCE CHARACTERISTICS Refer to the typical application schematic, TAMB= +27C
Figure 1: Fast VIN Startup (Scope: 50s/div)
CH 1: Switch Node, 5V/ div CH 2: Inductor Current, 1A/ div CH 3: VOUT, 1V/ div CH 4: VIN, 5V/ div
Figure 2: Load Transient 0mA to 600mA
CH 1: Output Voltage, 100mV per division ACCoupled CH 2: Load Current, 500mA/ div CH 3: Inductor Current, 500mA/ div
Figure 3: Load Transient 50mA to 650mA
CH 1: Output Voltage, 100mV per division ACCoupled CH 2: Load Current, 500mA/ div CH 3: Inductor Current, 500mA/ div
Figure 4: Load Transient 100mA to 700mA
CH 1: Output Voltage, 100mV per division ACCoupled CH 2: Load Current, 500mA/ div CH 3: Inductor Current, 500mA/ div
Date: 07/20/05
SP6659 1.5MHz, 600mA Synchronous Buck Regulator
(c) Copyright 2005 Sipex Corporation
3
TYPICAL PERFORMANCE CHARACTERISTICS
SP6659 Efficiency vs. Load Current VOUT = 1.2V 100 90 80 70 60 50 40 1 10 100 1000 Load Current (mA)
Figure 5: Efficiency Vs. Load Current, Vout =1.2V
Efficiency (%)
Vin = 2.7V Vin = 3.3V Vin = 4.2V
100 90
Efficiency (%)
SP6659 Efficiency vs. Load Current VOUT = 1.8V
80 70 60 50 40 1 10 100 1000 Load Current (mA)
Figure 6: Efficiency Vs. Load Current, Vout =1.8V
Vin = 2.7V Vin = 3.3V Vin = 4.2V
Date: 07/20/05
SP6659 1.5MHz, 600mA Synchronous Buck Regulator
(c) Copyright 2005 Sipex Corporation
4
FUNCTIONAL DIAGRAMS
OSC
SLOPE COMP
4 CIN
+ -
VIN 2.7 - 5.5V
BLANKING
+
ISENSE COMP R
-
VOUT
5 R1
0.6V
+ EA -
+ COMP -
Q _ Q RS LATCH PWM LOGIC DRV
_ S _ R
SW
3
NONOVERLAP CONTROL
VOUT
0.65V
+ OV DET + Izero COMP 0.6V
R2
VIN
COUT
2
RUN
1 REF
GND
SHUTDOWN
Fixed Output Version
OSC
SLOPE COMP
4
BLANKING
ISENSE COMP
+
R
CIN
+ -
VIN 2.7 - 5.5V
-
VFB
5
0.6V
+ EA -
+ COMP + OV DET -
Q _ Q RS LATCH
_ S _ R
PWM LOGIC
SW
3 R1 COUT
NONOVERLAP CONTROL
DRV
VOUT
C2
0.65V
VIN
RUN
1 REF
+ Izero COMP 0.6V SHUTDOWN
R2
2
GND
Adjustable Output Version
Date: 07/20/05
SP6659 1.5MHz, 600mA Synchronous Buck Regulator
(c) Copyright 2005 Sipex Corporation
5
APPLICATION INFORMATION
V OUT
(R)
A resistive divider based on the following equation determines the output voltage: VOUT = 0.6 (1+ R2 ) R1
R2
SP6659
V FB
R1 GND
The external resistive divider is connected to the output as shown in Figure 7 .
Figure 7: Setting the SP6659 Output Voltage.
THEORY OF OPERATION
The SP6659 is a monolithic switching mode Step-Down DC-DC converter. It utilizes internal MOSFETs to achieve high efficiency and can generate very low output voltage by using its internal reference at 0.6V. It operates at a fixed switching frequency, and uses slope compensated, current-mode architecture. This Step-Down DC-DC converter supplies 600mA of output current at VIN = 3V. The entire input voltage range is from 2.5V to 5.5V. __________________ CURRENT MODE PWM CONTROL Slope compensated current mode PWM control provides stable switching and cycleby-cycle current limit for excellent load and line responses and protection of the internal main switch (P-Channel MOSFET) as well as the synchronous rectifier (N-Channel MOSFET). During normal operation, the internal P-Channel MOSFET is turned on for a certain time to ramp the inductor current at each rising edge of the internal oscillator, and switched off when the peak inductor current is above the error voltage. The
current comparator, ICOMP, limits the peak inductor current. When the main switch is off, the synchronous rectifier will be turned on immediately and stay on until either the inductor current starts to reverse, as indicated by the current reversal comparator, IZERO, or the beginning of the next clock cycle. The OVDET comparator controls output transient overshoots by turning the main switch off and keeping it off until the fault is no longer present. _______________________ IDLE MODE OPERATION At very light loads, the SP6659 automatically enters Idle Mode (Figure 8). In the Idle Mode, the inductor current may reach zero Amps or reverse on each pulse. The PWM control loop will automatically skip pulses to maintain output regulation. The bottom MOSFET is turned off by the current reversal comparator, IZERO, and the switch voltage will ring. This is discontinuous mode operation, and is normal behavior for the switching regulator.
Date: 07/20/05
SP6659 1.5MHz, 600mA Synchronous Buck Regulator
(c) Copyright 2005 Sipex Corporation
6
THEORY OF OPERATION _______________________ DROPOUT OPERATION When the input voltage decreases toward the value of the output voltage, the SP6659 allows the main switch to remain on for more than one switching cycle and increases the duty cycle until it reaches 100%. The duty cycle D of a step-down converter is defined as:
D = TON X
________________________ MAXIMUM LOAD CURRENT The SP6659 will operate with an input supply voltage as low as 2.5V, however, the maximum load current decreases at lower inputs due to a large IR drop on the main switch and synchronous rectifier. The slope compensation signal reduces the peak inductor current as a function of the duty cycle to prevent sub-harmonic oscillations at duty cycles greater than 50%. Conversely, the current limit increases as the duty cycle decreases. _______________________ INDUCTOR SELECTION For most designs, the SP6659 operates with inductors of 1H to 4.7H. Low inductance values are physically smaller but require faster switching, which can result in some efficiency loss. The inductor value can be derived from the following equation:
OSC
X 100%
VOUT X 100% VIN
L = VOUT X (VIN - VOUT) VIN X IL X OSC
Figure 8. SP6659 Idle Mode Operation
where TON is the main switch on time, and OSC is the oscillator frequency (1.5Mhz). The output voltage then is the input voltage minus the voltage drop across the main switch and the inductor. At low input supply voltage, the R DSON of the P-Channel MOSFET increases, and the efficiency of the converter decreases. Caution must be exercised to ensure that the heat dissipated does not exceed the maximum junction temperature of the IC.
Where IL is the inductor Ripple Current. Large value inductors lower ripple current and small value inductors result in higher ripple current. Choose inductors at ripple current of approximately 35% of the maximum load current 600mA, or ~ 210mA. For output voltages above 2.0V, when lightload efficiency is important, the minimum recommended inductor is 2.2H. For optimum voltage-positioning load transients, choose an inductor with DC series resistance in the 50m to 150m range. For higher efficiency at heavy loads (above
Date: 07/20/05
SP6659 1.5MHz, 600mA Synchronous Buck Regulator
(c) Copyright 2005 Sipex Corporation
7
THEORY OF OPERATION 200mA), or minimal load regulation (but some transient overshoot), the resistance should be kept below 100m. The DC current rating of the inductor should be at least equal to the maximum load current plus half the ripple current to prevent core saturation (600mA+105mA). Table 1 lists some typical surface mount inductors that meet target applications for the SP6659. ________________ INPUT CAPACITOR SELECTION The input capacitor reduces the surge current drawn from the input and switching noise from the device. The input capacitor impedance at the switching frequency shall be less than input source impedance to prevent high frequency switching current from passing to the input. A low ESR (Equivalent Series Resistance) input capacitor sized for maximum RMS current must be used. Ceramic capacitors with X5R or X7R dielectrics are highly recommended because of their low ESR and small temperature coefficients. A 4.7F ceramic capacitor for most applications is sufficient. ______________ OUTPUT CAPACITOR SELECTION The output capacitor is required to keep the output voltage ripple small and to ensure regulation loop stability. The output capacitor must have low impedance at the switching frequency. Ceramic capacitors with X5R or X7R dielectrics are recommended due to their low ESR and high ripple current. The output ripple VOUT is determined by:
Part #
L (H)
Max DCR (m) 56.2 71.2 86.2 108.7
Rated DC Current (Amps) 2.52 1.5 1.44 1.15
Size WxLxH (mm)
1.4 Sumida CR43 2.2 3.3 4.7 1.5 Sumida CDRH4D18 2.2 3.3 4.7 1.5 Toko D312C 2.2 3.3 4.7
4.5x4.0x3.5
75 110 162 120 140 180 240
1.32 1.04 0.84 1.29 1.14 0.98 0.79 3.6x3.6x1.2 4.7x4.7x2.0
Table 1: Typical Surface Mount Inductors
VOUT
VOUT X (VIN - VOUT) VIN X L X OSC
+ X ESR
{
1
(8X OSC X COUT)
}
Date: 07/20/05
SP6659 1.5MHz, 600mA Synchronous Buck Regulator
(c) Copyright 2005 Sipex Corporation
8
PACKAGE: 5 PIN TSOT23
D e1
N
N/2 +1 E/2
E1/2 B E1 E B SEE VIEW C
VIEW A-A
INDEX AREA (D/2 X E1/2) 1 e b 2 N/2
O1
Gauge Plane Seating Plane o1 L1 L o
VIEW C
5 Pin TSOT JEDEC MO-193 (AB) Variation MIN NOM MAX SYMBOL A 1.1 A1 0 0.1 A2 0.7 0.9 1 b 0.3 0.5 c 0.08 0.2 2.90 BSC D 0.95 BSC e 1.90 BSC e1 2.80 BSC E 1.60 BSC E1 L 0.3 0.45 0.6 0.60 REF L1 0.25 BSC L2 o 0 4 8 o1 4 10 12 Note: Dimensions in (mm)
BASE METAL
A
A2 SEATING PLANE C A1
SIDE VIEW
WITH PLATING
b
c
Section B-B
____________________________ THERMAL RESISTANCE Thermal Resistance is specified with approximately 1 square of 1 ounce of copper.
OJA .......................................................................220C/W OJC .......................................................................110C/W
Date: 07/20/05 SP6659 1.5MHz, 600mA Synchronous Buck Regulator (c) Copyright 2005 Sipex Corporation
9
ORDERING INFORMATION
Part Number Operating Temperature Range Package Type
SP6659EK1 ......... ...............................-40C to +85C ........................................................... 5 Pin TSOT23 SP6659EK1/TR .... ...............................-40C to +85C ........................................................... 5 Pin TSOT23 SP6659EK1-1.5 .... ...............................-40C to +85C ........................................................... 5 Pin TSOT23 SP6659EK1-1.5/TR...............................-40C to +85C .......................................................... 5 Pin TSOT23 SP6659EK1-1.8 .... ...............................-40C to +85C ........................................................... 5 Pin TSOT23 SP6659EK1-1.8/TR...............................-40C to +85C .......................................................... 5 Pin TSOT23 Available in lead free packaging. To order add "-L" suffix to part number. Example: SP6659EK1/TR = standard; SP6659EK1-L/TR = lead free /TR = Tape and Reel Pack quantity is 2,500 for TSOT23.
Corporation
ANALOG EXCELLENCE
Sipex Corporation Headquarters and Sales Office 233 South Hillview Drive Milpitas, CA 95035 TEL: (408) 934-7500 FAX: (408) 935-7600
Sipex Corporation reserves the right to make changes to any products described herein. Sipex does not assume any liability arising out of the application or use of any product or circuit described herein; neither does it convey any license under its patent rights nor the rights of others.
Date: 07/20/05
SP6659 1.5MHz, 600mA Synchronous Buck Regulator
(c) Copyright 2005 Sipex Corporation
10

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