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19-1892; Rev 0; 1/01
High-Side Power Supply
_______________General Description
The MAX1822 high-side supply, using a regulated charge pump, generates a regulated output voltage 11V greater than the input supply voltage to power high-side switching and control circuits. The MAX1822 allows low-resistance N-channel MOSFETs (FETs) to be used in circuits that normally require costly, less efficient P-channel FETs and PNP transistors. The highside output also eliminates the need for logic FETs in +5V and other low-voltage switching circuits. A +3.5V to +16.5V input supply range and a typical quiescent current of only 150A make the MAX1822 ideal for a wide range of line- and battery-powered switching and control applications where efficiency is crucial. Also provided is a logic-level power-ready output (PR) to indicate when the high-side voltage reaches the proper level. The MAX1822 comes in an 8-pin SO package and requires three inexpensive external capacitors. The MAX1822 is a pin-for-pin replacement to the MAX622.
____________________________Features
o +3.5V to +16.5V Operating Supply Voltage Range o Output Voltage Regulated to VCC + 11V (typ) o 150A (typ) Quiescent Current o Power-Ready Output
MAX1822
Ordering Information
PART MAX1822ESA TEMP. RANGE -40C to +85C PIN-PACKAGE 8 SO
________________________Applications
High-Side Power Control with N-Channel FETs Low-Dropout Voltage Regulators Power Switching from Low Supply Voltages H-Switches Stepper Motor Drivers Battery-Load Management Portable Computers
Typical Operating Circuit
+3.5V TO +16.5V
Pin Configuration
TOP VIEW
0.1F CERAMIC C1
1 7 6 C2 2
C1+ C1C2+ C2-
8 VCC VOUT MAX1822 PR GND 4 3 5
C3 C1+ +12.5V TO +27.5V C2PR 1 2 8 7 VCC C1C2+ VOUT
MAX1822
3 6 5 GND 4
SO
________________________________________________________________ Maxim Integrated Products
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High-Side Power Supply MAX1822
ABSOLUTE MAXIMUM RATINGS
VCC ......................................................................................+17V VOUT ....................................................................................+30V IOUT ..........................................................................25mA Continuous Total Power Dissipation (TA = +70C) 8-pin SO (derate 5.88mW/C above +70C)...............471mW Operating Temperature Range ...........................-40C to +85C Storage Temperature Range .............................-65C to +160C Lead Temperature (soldering, 10s) .................................+300C
Stresses beyond those listed under "Absolute Maximum Ratings" may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(VCC = +5V, TA = TMIN to TMAX, unless otherwise noted.)
PARAMETER Supply Voltage SYMBOL VCC IOUT = 0, VCC = 3.5V, C1 = C2 = 0.047F, C3 = 1F IOUT = 0, VCC = 4.5V, C1 = C2 = 0.047F, C3 = 1F IOUT = 0, VCC = 16.5V, C1 = C2 = 0.01F, C3 = 1F (Note 2) High-Side Voltage (Note 1) VOUT IOUT = 50A, VCC = 3.5V, C1 = C2 = 0.047F, C3 = 1F IOUT = 250A, VCC = 5V, C1 = C2 = 0.047F, C3 = 1F IOUT = 500A, VCC = 16.5V, C1 = C2 = 0.01F, C3 = 1F (Note 2) Power-Ready Threshold Power-Ready Output High Power-Ready Output Low Output Voltage Ripple Switching Frequency PRT PROH PROL VR FO IOUT = 0, VCC = 5V, C1 = C2 = 0.047F, C3 = 1F, TA = +25C IOUT = 0, VCC = 16.5V, C1 = C2 = 0.047F, C3 = 1F, TA = +25C IOUT = 0 (Note 3) ISOURCE = 100A ISINK = 1mA C1 = C2 = 0.01F, C3 = 10F, IOUT = 1mA, VCC = 16.5V 50 90 150 150 500 A 350 CONDITIONS MIN 3.5 11.5 14.5 26.5 8.5 15 26.5 12 3.8 13.5 4.3 12.5 15.5 27.5 10.5 TYP MAX 16.5 16.5 17.5 29.5 V 16.5 18 29.5 14.5 5 0.4 V V V mV kHz UNITS V
Quiescent Supply Current
IQ
Note 1: High-side voltage measured with respect to ground. Note 2: For VCC > +13V on the MAX1822, use C1 = C2 = 0.01F. Note 3: Power-Ready Threshold is the voltage with respect to ground at VOUT when PR switches high (PR = VCC).
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High-Side Power Supply
__________________________________________Typical Operating Characteristics
MAX1822 SUPPLY CURRENT vs. C3 CAPACITOR VALUE
MAX1822 toc01
MAX1822
MAX1822 SUPPLY CURRENT vs. C3 CAPACITOR VALUE
VCC = +16.5V IOUT = 0 TA = +25C C1 = C2 = 0.01F
MAX1822 toc02
400 C* = 0.01F 350 SUPPLY CURRENT (A) 300 250 200 150 100 C* = 0.1F 50 1 2 3 4 5 6 VCC = +5V, IOUT = 0 TA = +25C C1 = C2 = C* 7 8 9 C* = 0.022F C* = 0.047F C* = 0.033F
400 350 SUPPLY CURRENT (A) 300 250 200 150 100 50
10
1
2
3
4
5
6
7
8
9
10
C3 CAPACITOR VALUE (F)
C3 CAPACITOR VALUE (F)
MAX1822 SUPPLY CURRENT vs. SUPPLY VOLTAGE
MAX1822 toc03
MAX1822 MAXIMUM OUTPUT CURRENT vs. C1 = C2 CAPACITOR VALUE
900 800 MAXIMUM IOUT (A) 700 600 500 400 300 200 100 0 NOTE: MAXIMUM IOUT IS THE LOAD CURRENT AT THE POINT WHERE VOUT BEGINS TO LOSE REGULATION. 0.01 C1 = C2 CAPACITANCE VALUE (F) 0.1 VCC = +5V C3 = 10F TA = +25C
MAX1822 toc04
1.4 1.2 SUPPLY CURRENT (mA) 1.0 0.8 0.6 C1 = C2 = 0.01F 0.4 0.2 0 2 4 6 8 10 VCC (V) 12
IOUT = 0 C3 = 1F TA = +25C
1000
C1 = C2 = 0.47F
14
16
18
MAX1822 OUTPUT VOLTAGE vs. OUTPUT CURRENT
VCC = +5V C3 = 10F TA = +25C C1 = C2 = 0.47F VOUT (V) VOUT (V) 15
MAX1822 toc05
MAX1822 OUTPUT VOLTAGE vs. OUTPUT CURRENT
VCC = +12V C3 = 10F TA = +25C C1 = C2 0.047F C1 = C2 0.01F C1 = C2 0.022F
MAX1822 toc05
17
24 23 22 21 20
16
14 C1 = C2 = 0.22F C1 = C2 = 0.01F 12 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 IOUT (mA) 18 0
13
19
1
2
3
4
5
6
7
8
9
10
IOUT (mA)
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High-Side Power Supply MAX1822
Typical Operating Characteristics (continued)
MAX1822 OUTPUT VOLTAGE RIPPLE vs. RESERVOIR CAPACITOR C3
MAX1822 toc07
MAX1822 TURN-ON TIME vs. SUPPLY VOLTAGE
IOUT = 0 TA = +25C
MAX1822 toc08
200 180 160 VOUT RIPPLE (mV) 140 120 100 80 60 40 20 0 1
TA = +25C
10
TURN-ON TIME (ms) 9 10
VCC = +16.5V IOUT = 1mA C1 = C2 = 0.01F VCC = +5V IOUT = 500A C1 = C2 = 0.047F
1
0.1 2 3 4 5 6 7 8 0 5 10 VCC (V) 15 20 RESERVOIR CAPACITOR (F)
Pin Description
PIN 1 2 3 4 5 6 7 8 NAME C1+ C2PR GND VOUT C2+ C1VCC FUNCTION Positive terminal to primary charge-pump capacitor Negative terminal to secondary charge-pump capacitor Power-Ready Output. High when VOUT is VCC + 8.5V with respect to GND. Ground High-Side Voltage Out Positive terminal to secondary charge-pump capacitor Negative terminal to primary charge-pump capacitor Input Supply
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_______________________________________________________________________________________
High-Side Power Supply MAX1822
VOUT
S8 11V 8.5V
C3 VINT
S7 C2 S6 S4 RC OSCILLATOR + CONTROL LOGIC OVERVOLTAGE COMPARATOR
POWER-READY COMPARATOR
S3 VCC C1 S2 PR PR DRIVER S1 S5
GND TWO-STAGE CHARGE PUMP (SWITCHES SHOWN IN REFRESH MODE)
Figure 1. MAX1822 Block Diagram
Detailed Description
Charge-Pump Operation
The MAX1822 is a multistage charge-pump power supply. Although the charge pump is capable of multiplying VCC up to four times, the output is regulated to VCC + 11V by an internal feedback circuit for inputs above 4V. The charge pump typically operates at 90kHz, but regulates by pulse skipping. When VOUT exceeds VCC + 11V, the oscillator shuts off. As VOUT dips below VCC + 11V, the oscillator turns on.
VOUT reaches approximately VCC + 8.5V. PR also goes low if VOUT falls below this level during operation, i.e., if the output is overloaded. The PR high level is VCC.
Applications Information
Quiescent Supply Current
MAX1822 quiescent supply current varies with VCC and with the values of C1, C2, and C3 (Typical Operating Characteristics). Even with no external load, the device must still pump to overcome internal losses. Large ratios between C3 and C1 or C2 require more charge-pump cycles to restore VOUT. As VCC falls below 5V, quiescent current rises fairly rapidly to about 1mA at 4V (Typical Operating Characteristics). This rise occurs because VOUT no longer pulse skips to regulate at low input voltages; the oscillator runs continuously, so supply current is higher. Figure 2 shows the test circuit for the MAX1822 quiescent supply current.
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Power-Ready Output
The Power-Ready Output (PR) signals control circuitry when the high-side voltage reaches a preset level. This feature can be used to protect external FET switches from excess dissipation and damage by preventing them from turning on, except when adequate gate drive levels are present. When power is applied, PR remains low until
_______________________________________________________________________________________
High-Side Power Supply MAX1822
Output Ripple
C3 1.0F VSUPPLY A 1 C2 0.047F V 6 C2 0.047F 2 C2+ C2MAX1822 7 8 VCC VOUT 5
C4 1000F LOW ESR
C1+ C1-
VOUT ripple is typically 50mVp-p with VCC = +5V, C1 and C2 = 0.047F, and C3 = 1F (Typical Operating Characteristics). Ripple can be reduced by increasing the ratio between the output storage capacitors C3 and C1 and C2. This is usually accomplished by increasing C3 and keeping C1 and C2 in the 0.01F to 0.047F range. For example, if C1 and C2 are 0.047F (VCC must not exceed 13V) and C3 is 10F, output ripple typically falls to 15mV (Typical Operating Characteristics).
GND 4
Capacitor Selection
Capacitor type is unimportant when selecting capacitors for the MAX1822. However, when VCC exceeds 13V, C1 and C2 must be no greater than 0.01F. Using larger value capacitors with input voltages above 13V causes excessive amounts of energy to pass through
Figure 2. MAX1822 Quiescent Supply-Current Test Circuit
6-CHANNEL LOAD SWITCH +5V C4 1F VOUT 5 C3 10F
8 1 C2 0.047F 7 6 C2 0.047F 2 C1+ C1C2+ C2MAX1822 VCC
ALL PULLUP RESISTORS = 1M
ALL TRANSISTORS = 1RF541 (NOTE 2) TO 1A LOAD
14 74C906
TO 1A LOAD
GND 4 2 1 TO 1A LOAD 4 3
TO 1A LOAD 6 SW1 SW2 SW3 SW4 SW5 SW6 12 13 ALL CAPACITORS = 1F (NOTE 1) 7 NOTE 1: 1F CAPACITORS SUPPRESS SWITCHING TRANSIENTS, SIZE DEPENDS ON LOAD CURRENTS. NOTE 2: POWER TRANSISTOR TYPE DEPENDS ON LOAD-CURRENT REQUIREMENTS. 10 11 TO 1A LOAD 8 9 TO 1A LOAD 5
Figure 3. Single MAX1822 Driving Six High-Side Switches 6 _______________________________________________________________________________________
High-Side Power Supply MAX1822
H-BRIDGE MOTOR CONTROL +5V 14 8 1 C1 0.047F 7 6 C2 0.047F 2 C2GND 4 REVERSE FORWARD C1MAX1822 C2+ 6 9 IN1 IN2 GND 7 D3 3 DG303 S3 S1 D4 12 5 IRF541 IRF541 C1 VCC VOUT 5 V+ C3 10F 4 D1 S2 10 IRF541 IRF541
11
D2
S4 13
DC MOTOR +5V
+
-
Figure 4. H-Bridge Motor Controller
internal switches during charge-pump cycles. This may damage the device.
high-side output current from the MAX1822 at a given supply voltage, calculated as follows: RMIN = VOUT x (number of channels) IOUT
Output Protection
The MAX1822 is not internally short-circuit protected. In applications where the output is susceptible to short circuit, external output short-circuit protection must be provided. Accomplish this by connecting a resistor between VOUT and the load to limit output current to less than 25mA. The resistor value is determined by the following formula: RCL VCC 25mA
where VOUT is the high-side output voltage and IOUT is the output current of the MAX1822. For example, assuming an output current of 1mA and six channels, as in Figure 3, the minimum pullup resistor value that will not excessively load the MAX1822 is about 100k, assuming all six channels are pulled low at the same time. The value of the pullup resistor also affects the turn-on time of each FET, and hence the amount of energy dissipated in the FET during turn-on. The rate of rise of VGS is limited by the RC time constant of the pullup resistor and FET gate capacitance; waste power will be dissipated in the FET equal to (ILOAD)2 x rDS during the RC time period.
Typical Applications
One MAX1822 Drives Six High-Side Switches
Multiple subsystems or modules can be turned on and off using a single MAX1822 and an open-drain hex buffer such as the 74C906 (Figure 3). The drains of all buffer outputs are pulled through resistors to the MAX1822's VOUT. The pullup resistance depends on the number of channels being used with the MAX1822 and power-dissipation limitations. The minimum pullup resistor value is determined by the number of channels paralleled on each high-side power supply and the
H-Bridge Motor Driver
An H-bridge motor driver is shown in Figure 4. The motor direction can be controlled by toggling between IN1 and IN2 of the DG303 analog switch. Each switch section turns on the appropriate FET pair, which passes current through the motor in the desired direction.
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High-Side Power Supply MAX1822
4-CHANNEL LOAD SWITCH--NO PULLUP RESISTORS +3.5V TO +16.5V C3 10F C4 1F 1 C1 0.01F 7 6 C2 0.01F C1MAX1822 C2+ 12 19 4 2 C2GND 4 7 14 17 C1+ 8 VCC VOUT 5 16 V+ 2 N01 9 N02 N03 N04 NC1 NC2 NC3 NC4 COM4 18 MAX333 13 COM2 8 COM1 3
ALL TRANSISTORS = IRF541 (NOTE 1) TO LOAD
TO LOAD
TO LOAD COM3
TO LOAD
5 VIN1 NOTE 1: TRANSISTOR TYPE DEPENDS ON LOAD-CURRENT REQUIREMENTS. NOTE 2: 1F CAPACITORS SUPRESS SWITCHING TRANSIENTS--VALUE DEPENDS ON LOAD CURRENT. 1 SW1 SW2 SW3 SW4 IN2 10 IN3 11 IN4 20
ALL CAPACITORS = 1F (NOTE 2)
Figure 5. MAX1822 Powering a MAX333 Quad Analog Switch, Realizing a 4-Channel Load Switch with No Pullup Resistors
4-Channel Load Switch with No Pullup Resistors
Multiple high-side switches can be driven from a single MAX1822 high-side power supply with no pullup resistors on the FET gates. In Figure 5, a MAX1822 supplies high-side voltage to a MAX333 quad analog switch to control any one of four high-side switches. The FET gates are normally connected to ground when the MAX333 logic inputs are low.
depends on the magnitude of the load change in the application and can be reduced or eliminated if the load remains relatively constant. With C6 = 1000F, the output transient to a 1A load pulsed at 20Hz is typically less than 150mV. The regulator is turned on by applying VBATT to the Enable/Shutdown input and turned off by pulling this input to ground. The regulator output voltage, VOUT, is set by the ratio of R1 to R2, calculated as follows: V R2 = R1 OUT - 1 0.2 If the application does not require logic shutdown, connect the MAX1822 VCC pin directly to the battery and eliminate D2.
Low-Dropout Regulator
In Figure 6, a MAX1822 high-side power supply powers an LM10 reference and op-amp combination, providing sufficient gate drive to turn on the FET. This allows the regulator to achieve less than 70mV dropout at 1A load using an IRF541, and just under 20mV for a SMP60N06. The 200mV reference section is configured for a gain of 25 (e.g., 200mV x 25 = 5V) and connects to the noninverting input of the op amp; the regulator's output connects directly to the inverting input. The op amp amplifies the error between its inputs and varies the gate drive to the FET, regulating the output. Capacitor C6 reduces transients due to load changes; its size
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_______________________________________________________________________________________
High-Side Power Supply MAX1822
C4 0.1F 225 C5 0.1F 1 C1 0.01F 7 6 C2 0.01F C1C2+ 2 2 C1+ 200 5 R2 24k 3 7 1 R1 8 6 1k Q1 IRF541 VBATT DROPOUT VOLTAGE (mV) 8 VCC C3 10F VOUT 175 150 125 100 75 50 25 C6 1000F +5V 0 0.1
DROPOUT VOLTAGE vs. LOAD CURRENT
TA = +25C
MAX1822 Fig 06
MAX1822
PR
D1 R3 1k 3 1N914
IRF541
IRFZ40
LM10 4
SMP60N06
C2-
GND 4
1 LOAD CURRENT (A)
10
ENABLE/SHUTDOWN
D2 1N914
Figure 6. Ultra-Low Dropout Positive Voltage Regulator with Logic-Controlled Enable/Shutdown.
Chip Information
TRANSISTOR COUNT: 158
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High-Side Power Supply MAX1822
________________________________________________________Package Information
SOICN.EPS
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
10 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 (c) 2001 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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