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19-0329; Rev 0; 12/94
UAL IT MAN TION K T VALUA A SHEE E T WS DA FOLLO
High-Accuracy, Low-Dropout Linear Regulators
____________________________Features
o Fixed Outputs: 3.3V (MAX687/MAX688) 3.0V (MAX689) o Directly Drives External PNP Transistor o 10mA Min Base-Current Drive for >1A Output o Low Dropout Voltage: 100mV Dropout at 650mA Output (FZT749) 40mV Dropout at 200mA Output (FZT749) 0.8V Dropout at 4A Output o Power-Fail Output Monitors the Output Voltage o Automatic, Latched Shutdown when Output Falls Out of Regulation (MAX687) o Precision Threshold Shutdown Control (MAX688/MAX689) o Low Supply Current: 150A Operating <1A Shutdown o 2.7V to 11.0V Supply Range o 8-Pin DIP/SO/MAX Packages o <2mV Line Transient with 3.4V to 3.6V Input o Output Accuracy <2%
_______________General Description
The MAX687/MAX688/MAX689 low-dropout linear regulators operate with an input-to-output voltage differential limited only by an external PNP transistor. Outputs are fixed at 3.3V (MAX687/MAX688) or 3.0V (MAX689). The only external components required are a PNP pass transistor and output, compensation, and bypass capacitors. Base drive to the external transistor is at least 10mA, permitting output currents to exceed 1A when using high-gain transistors ( > 100). Output current limiting is implemented by limiting the external transistor's base current. Output voltage monitoring and shutdown functions are included. The 3.3V MAX687 automatically shuts down whenever the output voltage drops below 2.96V. An internal power-fail comparator also monitors the output and provides an early warning of low output voltage before the device shuts down. When shut down, the output is latched off until the ON input is pulsed. Turning off the power supply in this way prevents battery damage due to excessive discharge or cell-reversal. Typical applications include portable telephones and other battery-powered equipment where the power supply must be disabled when the battery voltage is low. The MAX688 and MAX689 do not have an automatic shutdown function, and are identical except for their output voltages. Each device has an active-low shutdown-control input, used to turn its output on or off at any time. As SHDN falls, the device enters a standby mode before fully shutting down. When in standby, the reference and comparators are fully operational, permitting the transition from normal mode to standby mode to occur at a precise voltage level on SHDN.
MAX687/MAX688/MAX689
______________Ordering Information
PART MAX687CPA MAX687CSA MAX687CUA MAX687EPA MAX687ESA TEMP. RANGE 0C to +70C 0C to +70C 0C to +70C -40C to +85C -40C to +85C PIN-PACKAGE 8 Plastic DIP 8 SO 8 MAX 8 Plastic DIP 8 SO
________________________Applications
High-Efficiency Linear Regulator Battery-Powered Devices Portable Instruments Portable Telephones Power Supply or Backup Supply for Memory
Ordering Information continued at end of data sheet.
__________Typical Operating Circuit
+3.5V to +5V INPUT Q1 FZT749 RB 12 3.3V @ 500mA
__________________Pin Configuration
TOP VIEW
IN IN 1 (ON) SHDN 2 PFO 3 GND 4 ( ) ARE FOR MAX687 8 CC BASE BLIM OUT GND C1 2.2F ON ON 7 6 5 BASE
BLIM OUT C2 68F PFO CC GND C3 10nF POWER-FAIL OUTPUT
MAX687 MAX688 MAX689
MAX687
DIP/SO/MAX
________________________________________________________________ Maxim Integrated Products
1
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High-Accuracy, Low-Dropout Linear Regulators MAX687/MAX688/MAX689
ABSOLUTE MAXIMUM RATINGS
Input Supply Voltage IN to GND ............................................12V Terminal Voltages to GND PFO (MAX687) ........................................-0.3V to VOUT + 0.3V PFO (MAX688/MAX689) ......................................-0.3V to 12V All Remaining Pins .....................................-0.3V to VIN + 0.3V PFO Sink Current ...............................................................10mA PFO Source Current (MAX687)...........................................10mA Continuous Power Dissipation (TA = +70C) Plastic DIP (derate 9.09mW/C above +70C) ............727mW SO (derate 5.88mW/C above +70C) .........................471mW MAX (derate 4.1mW/C above +70C) ......................330mW Operating Temperature Ranges MAX68_C_A .......................................................0C to +70C MAX68_E_A ....................................................-40C to +85C Storage Temperature Range .............................-65C to +165C Lead Temperature (soldering, 10sec) .............................+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
(VIN = 3.8V, SHDN = VIN (MAX688/MAX689), RB = 0, C1 = 2.2F, C2 = 10F, C3 = 10nF, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25C.) PARAMETER LINEAR REGULATOR Supply Voltage VIN (Note 1) VIN = 3.8V, IBASE = 1mA MAX687/MAX688 Output Voltage VOUT MAX689 Dropout Voltage (Note 2) 3.8V VIN 11.0V, 1A IBASE 10mA VIN = 3.5V, IBASE = 1mA 3.5V VIN 11.0V, 1A IBASE 10mA 3.8V VIN 11.0V, IBASE = 1mA 3.5V VIN 11.0V, IBASE = 1mA On Supply Current IGND VIN = 3.8V, PNP = FZT749, no load VBASE = VIN - 1V RB is connected from BASE to BLIM (), RB = 0 to 100 (Note 3) C2 PNP = FZT749, ILOAD = 100mA (Note 4) 10 Standby, MAX688/MAX689 Shutdown BASE Sink Current Base-Current Limit Start-Up Time Start-Up Overshoot Load Capacitance IBASE 10 2.7 3.2 3.13 2.9 2.85 3.3 3.3 3.0 3.0 40 0.4 0.4 45 150 11 < 0.02 20 1.4 mV/V 1.4 60 250 25 1 40 mA mA s % F A mV 11.0 3.4 3.47 3.1 3.15 mV V V SYMBOL CONDITIONS MIN TYP MAX UNITS
VIN - VOUT PNP = FZT749, ILOAD = 200mA, C2 = 20F MAX687/MAX688
Line Regulation MAX689 Load Regulation 1A IBASE 10mA
70 100 130 RB + 5 RB + 5 RB + 5 300 2
2
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High-Accuracy, Low-Dropout Linear Regulators
ELECTRICAL CHARACTERISTICS (continued)
(VIN = 3.8V, SHDN = VIN (MAX688/MAX689), RB = 0, C1 = 2.2F, C2 = 10F, C3 = 10nF, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25C.) PARAMETER MAX687: ON, PFO, SHDN PFO Threshold Voltage Below VNOM (Note 5) PFO Hysteresis Shutdown Threshold Voltage Below VPFT Shutdown Threshold Voltage PFO Output Voltage High PFO Output Voltage Low ON Threshold Voltage ON Input Leakage Current MAX688/MAX689: SHDN, PFO PFO Threshold Voltage PFO Hysteresis VSON SHDN Threshold Voltages SHDN Hysteresis SHDN Input Current PFO, SHDN Transient Rejection PFO Output Voltage Low PFO Off Leakage Current Output Noise Voltage en VOL VSSY VSSD On, SHDN falling Standby Shutdown Rising SHDN, standbyon V SHDN = 1.23V Glitch immunity ISINK = 1.2mA, VIN = 2.7V V PFO = 11V, V SHDN > 1.25V 10Hz f 10kHz, ILOAD = 200mA 10Hz f 1MHz, ILOAD = 200mA 66 105 -25 100 0.06 0.3 1 70 25 1.25 1.0 1.2 0.2 mV nA s V A VRMS V VPFT Falling VOUT, comparators monitor VOUT MAX688 MAX689 3.07 2.77 3.13 2.85 7 3.19 2.89 V mV VPFT - VSD Falling VOUT, comparators monitor VOUT VSD VOH VOL VIH VIL Falling VOUT, comparators monitor VOUT ISOURCE = 50A, part on, VIN = 2.7V ISINK = 1.2mA, VIN = 2.7V Output turns on Output remains off 0.2 1.0 0.2 100 20 2.96 VOUT - 0.3 0.06 0.3 VNOM VPFT Falling VOUT, comparators monitor VOUT 110 170 7 70 mV mV mV V V V V nA SYMBOL CONDITIONS MIN TYP MAX UNITS
MAX687/MAX688/MAX689
Note 1: Minimum VIN for regulated VOUT depends on the characteristics of the external PNP transistor, and on the load. The reference and comparators are functional down to the minimum voltage specified, but the output may not be in regulation. Note 2: Dropout voltage is defined as VIN - VOUT when VOUT is 50mV below its value at VIN = VNOM + 1V. Note 3: The start-up time specification is the time taken from ON or SHDN rising to BASE sinking current. VOUT rise time is longer and is a function of load capacitance, C2, and load resistance, RL. Note 4: Minimum load capacitance is a function of RL. Minimum C2 = 10F for loads up to 100mA and 1F/10mA for higher loads. ESR of C2 should be no larger than 1/100 of RL. Guaranteed by design. Note 5: The nominal output voltage, VNOM, is defined under the default conditions of testing: VIN = 3.8V, IBASE = 1mA, TA = TMIN to TMAX.
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High-Accuracy, Low-Dropout Linear Regulators MAX687/MAX688/MAX689
__________________________________________Typical Operating Characteristics
(Circuits of Figures 1 and 2, VIN = 5V, Q1 = FZT749, TA = +25C, unless otherwise noted.)
MAX687 OUTPUT VOLTAGE DISTRIBUTION
3.31932 3.31576
MAX687/9-02
MAX688 OUTPUT VOLTAGE DISTRIBUTION
3.32145 3.31920 3.31696 3.31472 3.31248 3.31024 3.30800 3.30576 3.30352 3.30128 3.29904 3.29679 3.29455 3.29231 3.29007 3.28783 3.01595 3.01420 3.01245
MAX687/9-01
MAX689 OUTPUT VOLTAGE DISTRIBUTION
MAX687/9-03
3.32289
OUTPUT VOLTAGE (V)
3.30862 3.30505 3.30149 3.29792 3.29435 3.29078 3.28722 3.28365
OUTPUT VOLTAGE (V)
3.31219
OUTPUT VOLTAGE (V) 0 50 100 150 NUMBER OF UNITS 200 250
3.01071 3.00896 3.00721 3.00547 3.00372 3.00198 3.00023 2.99848 2.99674 2.99499 2.99324 2.99150 2.98975
0
50
100 150 NUMBER OF UNITS
200
250
0
50
100
150
200
250
NUMBER OF UNITS
DROPOUT VOLTAGE vs. LOAD CURRENT
MAX687/9-05
DROPOUT VOLTAGE vs. LOAD CURRENT
MAX687/9-5
GND CURRENT vs. LOAD CURRENT
MAX687/9-06
0.30 0.25 0.20 0.15 0.10 0.05 0 0 200 600 1000 1400 OBSERVE MAXIMUM POWER DISSIPATION LIMIT OF EXTERNAL PASS TRANSISTOR. Q1 = FZT749 RB = 0
1.0 0.9 0.8 Q1 = 2N2907 RB = 0
6 5 GND CURRENT (mA) 4 3 2 1 0
0.7 VIN - VOUT (V) 0.6 0.5 0.4 0.3 0.2 0.1 0 1800 0 200 400 600 800 1000 LOAD CURRENT (mA)
VIN - VOUT (V)
0
200
400
600
800
1000 1200
LOAD CURRENT (mA)
LOAD CURRENT (mA)
GND CURRENT vs. DROPOUT VOLTAGE
MAX687/9-7
GND CURRENT vs. DROPOUT VOLTAGE
MAX687/9-8
NO-LOAD SUPPLY CURRENT vs. TEMPERATURE
144 142 SUPPLY CURRENT (A) 140 138 136 134 132 130
MAX687/9-9
7 6 GND CURRENT (mA) 5 4 3 300mA LOAD 2 1 0 100mA LOAD 10mA LOAD
7 6 GND CURRENT (mA) 5 4 3 2 1 0 0 1 2 3 4 5 6 7 8 VIN - VOUT (V) 300mA LOAD 100mA LOAD 10mA LOAD
146
128 126 -55 -25 0 25 50 75 100 125 TEMPERATURE (C)
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 VIN - VOUT (V)
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High-Accuracy, Low-Dropout Linear Regulators
____________________________Typical Operating Characteristics (continued)
(Circuits of Figures 1 and 2, VIN = 5V, Q1 = FZT749, TA = +25C, unless otherwise noted.)
SHUTDOWN SUPPLY CURRENT vs. TEMPERATURE
MAX687/9-10
MAX687/MAX688/MAX689
OUTPUT VOLTAGE vs. TEMPERATURE
MAX687/9-11
MAX687/MAX688 RIPPLE REJECTION vs. FREQUENCY
70 RIPPLE REJECTION (dB) 60 50 40 30 20 10 C2 = 20F 0 VIN = 3.6V Min ILOAD = 200mA VIN = 4.3V Min ILOAD = 20mA
MAX687/9-16
0.3000 SHUTDOWN SUPPLY CURRENT (A) 0.2500 0.2000 0.1500 0.1000 0.0500 0 -55 -25 0 25 50 75 100
3.315 3.310 OUTPUT VOLTAGE (V) 3.305 3.300 3.295 3.290 3.285 3.280
80
125
-55
-25
0
TEMPERATURE (C)
25 50 75 TEMPERATURE (C)
100
125
10
100
1k 10k FREQUENCY (Hz)
100k
LINE-TRANSIENT RESPONSE
LINE-TRANSIENT RESPONSE
MAX687/MAX688 POWER-UP AND EXIT FROM SHUTDOWN
VOUT 3.3V 1mV/div
VOUT 3.3V 1mV/div
VIN 5V/div
VIN 3.6V VIN 3.4V ILOAD = 70mA C1 = 2.2F C2 = 20F C3 = 10nF 2ms/div ILOAD = 200mA C1 = 2.2F C2 = 20F C3 = 10nF 2ms/div
VIN 3.6V VIN 3.4V 1ms/div
VOUT 1V/div
SHDN 5V/div ILOAD = 500mA C1 = 2.2F C2 = 68F C3 = 10nF
LOAD-TRANSIENT RESPONSE
LOAD-TRANSIENT RESPONSE
VOUT 3.3V 10mV/div
VOUT 3.3V 10mV/div
500mA ILOAD 200mA/div 0mA 100s/div 100s/div
500mA ILOAD 200mA/div 0mA
VIN = 3.4V
VIN = 3.5V
_______________________________________________________________________________________
5
High-Accuracy, Low-Dropout Linear Regulators MAX687/MAX688/MAX689
______________________________________________________________Pin Description
PIN 1 NAME IN ON (MAX687) 2 2 SHDN (MAX688/ MAX689) SHDN is a three-level input that controls the mode of operation. The device is on when V SHDN > 1.25V. The output is disabled and the supply current is reduced (IIN < 25A, standby mode) when V SHDN < 1.2V, and is fully off (IIN < 1A, shutdown mode) when V SHDN < 0.2V. Connect SHDN to IN if the shutdown function is not used. PFO is low when SHDN is low (below 0.2V). Power-Fail Output. PFO trips when VOUT is 170mV below nominal VOUT at IBASE = 1mA. PFO sources and sinks current in the MAX687, but is an open drain in the MAX688/MAX689. When shut down, PFO is always low and sinks current. Leave PFO open if not used. Ground Regulator Output. MAX687/MAX688, 3.3V; MAX689, 3.0V. Base current limit. A resistor (RB) connected between BASE and BLIM sets the maximum base drive to the PNP transistor: IBASE 0.1V / (RB + 5). This limits quiescent current rise during dropout and also provides current limiting without using a current-sense resistor in the collector of the external PNP, thus not impacting dropout. Output current limiting accuracy depends on how well the external PNP beta (hFE) is controlled. Connect to BASE if not used. Base drive for the external PNP transistor. Current limiting is controlled using a resistor (RB) connected between BASE and BLIM. For maximum output current, connect BASE to BLIM. Compensation Capacitor. Connect a non-polarized capacitor (10nF to 100nF) from CC to GND. Positive input voltage, 2.7V to 11.0V ON activates the regulator when pulsed high. In order for the regulator to remain on, ON must remain high until VOUT exceeds the internal shutdown threshold voltage. The MAX687 is shut down when VOUT < 2.96V, and remains latched off until ON is pulsed high. When powered up, the MAX687 does not start up until ON is pulsed high. Connect to VIN if not used. FUNCTION
3 4 5
PFO GND OUT
6
BLIM
7 8
BASE CC
_______________Detailed Description
The MAX687/MAX688/MAX689 are precision lowdropout linear regulators employing external PNP transistors to achieve a wide range of output currents at voltages of 3.0V or 3.3V. The maximum base current for the PNP can be limited using a resistor. Limiting the base drive keeps high currents from being wasted when the device is in dropout (e.g., at low input voltages), and limits the regulator's output current. The dropout voltage is limited only by the PNP transistor's VCE(SAT). The Power-Fail Output (PFO) goes low when the output voltage drops 170mV below the nominal level. The three devices differ in their output voltages, in their shutdown-control functions, and in PFO's output drive (see Table 1).
Table 1. Device Functions
FUNCTION VOUT Shutdown Control PFO MAX687 3.3V Automatic at low VOUT. Latched. Use ON to start. Sources & Sinks MAX688 3.3V External SHDN Open Drain MAX689 3.0V External SHDN Open Drain
The MAX687's output voltage is internally monitored; a falling VOUT is signaled by PFO going low. As the output falls further, the MAX687 automatically enters a lowpower shutdown mode, where the base drive to the external PNP is cut off. PFO trips at a minimum of 110mV below the nominal VOUT, and shutdown occurs by 2.96V. PFO is guaranteed to trip before the device
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High-Accuracy, Low-Dropout Linear Regulators
shuts down. Once the MAX687 is shut down, it can only be turned on again when (a) the ON pin is pulsed high, and (b) the conditions that triggered shutdown have changed (e.g., the load has been reduced or the input voltage has increased). In order for the MAX687 to latch into its on state, the ON pulse must remain high until the output voltage has risen above the shutdown threshold. The internal shutdown can be used to prevent deep discharge of a battery, for example, to provide "self backup" of CMOS RAM or to protect the battery itself. The RC circuit attached to the ON input in Figure 1 achieves automatic start-up at power-on by delivering a brief pulse whenever the input voltage is suddenly applied. This circuit is not suitable for applications where the input voltage rises slowly. The RC values should be chosen to keep ON high until the output rises above about 3.13V. The values shown in Figure 1 for C4 and R1 (0.1F and 10k) are suitable for most applications. To ensure start-up when the input voltage is very close to the circuit's dropout voltage, when the circuit is used to drive a very large capacitive load, or for high-power circuits (ILOAD > 3A), increase the value of R1 to increase the ON pulse width. The 3.3V MAX688 and the 3.0V MAX689 incorporate the same PFO warning whenever V OUT droops. However, the MAX688/MAX689 do not automatically shut down when the output voltage drops even further. Instead, the SHDN input controls external shutdown. As SHDN is pulled low, the chip first enters a low-current standby state (<25A). The threshold at which standby mode is entered is precisely controlled (2%) so the output can be turned off at a well-defined point. 70mV of hysteresis between the standby and on states prevents chatter between the two modes. The voltage applied to the SHDN pin can be derived from a resistive divider from VIN. When VSHDN is less than 1.2V, the output is off. The device is fully shut down (<1A) when SHDN is pulled below 200mV. SHDN is not latched, and as SHDN is raised, the MAX688/MAX689 exit shutdown and enter the standby mode. At the higher SHDN threshold, the output is turned on. Figure 1 shows a typical circuit for the MAX687, and Figure 2 shows the same circuit configured for the MAX688/MAX689. The accuracy of the output current limit depends on accurate knowledge of the PNP pass transistor's current gain (hFE). With RB = 12, BLIM limits base current to 6mA (IBASE = 0.1V / (RB + 5)). See BaseCurrent Limiting section. The PFO comparators on all three devices, and the internal shutdown comparator on the MAX687, reject high-speed spikes (<100s). This reduces the PFO output's noise sensitivity, and stops the MAX687 from being shut down inadvertently when there is noise on the input supply.
MAX687/MAX688/MAX689
_______________Transistor Selection
Specifications
The PNP pass transistor must meet specifications for * current gain, * power dissipation, and * collector current. The hFE influences the maximum output current the circuit can deliver. The largest guaranteed output current
+5V INPUT
Q1 FZT749
3.3V @ 500mA
+5V INPUT
Q1 FZT749
3.3V/ 3.0V @ 500mA
RB 12 C4 0.1F C1 2.2F ON R1 10k GND ON CAN BE DRIVEN DIRECTLY FROM LOGIC WHEN R1 AND C4 ARE NOT USED. GND GND BASE IN BLIM OUT C2 68F PFO CC C3 10nF BASE IN POWER FAIL C1 2.2F ON / OFF
RB 12 BLIM OUT
R2 100k
MAX687
MAX688 MAX689
SHDN GND
C2 68F PFO CC C3 10nF POWER FAIL
Figure 1. MAX687 Operating Circuit
Figure 2. MAX688/MAX689 Operating Circuit
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High-Accuracy, Low-Dropout Linear Regulators MAX687/MAX688/MAX689
is given by ILOAD(MAX) = 10mA x hFE(MIN). The transistor's rated power dissipation must exceed the actual power dissipated in the transistor. The power dissipated (PD) equals the maximum load current (ILOAD(MAX)) times the maximum input to output voltage differential: PD = ILOAD(MAX) x (VIN(MAX) - VOUT). The rated transistor collector current must exceed the maximum load current. Suitable transistors include the Zetex FZT749, and the 2N2907A (see Table 2). Connect the bypass capacitor directly between pins 1 and 4 of the IC, using short leads. Connect the emitter of the PNP transistor directly to the bypass capacitor using a very short trace.
Output Capacitor (C2)
The output filter capacitor must be at least 10F. For currents above 100mA, use 1F of capacitance for every 10mA of load current (e.g., 20F for 200mA load, 50F for 500mA). Low-ESR capacitors give best stability and transient response. Ensure that the capacitor's ESR is less than 1% of the load resistance. See Table 2 for a list of manufacturers. Sanyo OS-CON capacitors are recommended for applications operating at temperatures below 0C.
Base-Current Limiting
A comparator monitors the voltage across the external base-current-limiting resistor (between BASE and BLIM). This sets the maximum base current. If BASE and BLIM are shorted, base current is limited nominally to 20mA due to an internal 5 resistor in series with the external resistance. Choose the base-current-limiting resistor, R B , so the drop across it at rated load is approximately 50mV. RB =
Compensation Capacitor (C3)
Connect a compensation capacitor from CC to GND. 10nF is recommended, although higher values (up to 100nF) may also be used. Higher C3 values eliminate power-on overshoot, but extend power-up times. Current flowing into or out of CC causes the regulator's reference voltage to change, resulting in shifted output voltage and trip thresholds. Use non-polarized capacitors (e.g., ceramic, polyester, etc.) to keep leakage currents below 25nA. Aluminum and tantalum electrolytic capacitors are unsuitable because of their high leakage currents.
(50mV) x hFE(MIN)
ILOAD(MAX)
- 5
The base drive is controlled so the voltage on BLIM is limited to 100mV below the voltage on BASE; with a 50mV nominal drop across RB + 5, base-current drive is limited to twice the nominal. This limits base current when the external PNP is heavily saturated, such as when the regulator is in dropout due to low input voltage. In addition, if the external PNP's hFE is defined within reasonable limits, base-current control effectively limits output current without a dropout voltage penalty.
__________________Power-Fail Output
The PFO output trips when VOUT is 170mV below nominal VOUT at IBASE = 1mA. PFO sources and sinks current in the MAX687, but is an open drain in the MAX688/MAX689 and only sinks current. When shut down, PFO is always low regardless of the voltage at OUT. Leave PFO open if it is not used.
________________Capacitor Selection
Bypass Capacitor (C1)
Connect a bypass capacitor from IN to GND. 4.7F makes the circuit insensitive to layout, and is sufficient for any load. Smaller values may be used--down to 0.33F--with low-ESR capacitors, good board layout, and a low-impedance incoming supply.
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High-Accuracy, Low-Dropout Linear Regulators
__________Applications Information
High-Power Output Circuit
Figure 3 shows a pseudo-Darlington transistor configuration to increase load-current capability and maintain a low dropout voltage with a 4A load. A heatsink must be added when high power is dissipated in the pass transistor. Figure 4 shows the (VIN - VOUT) voltage required to maintain regulation for different load currents. Figure 5 shows an oscilloscope plot of the transient response of a 200mA to 4A load step.
DROPOUT VOLTAGE vs. LOAD CURRENT
0.9 0.8 VIN - VOUT (V) 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 0 1000 2000 3000 4000 LOAD CURRENT (mA) Q1 = TIP42 Q2 = 2N4403 BASE = BLIM
MAX687/9-04
MAX687/MAX688/MAX689
1.0
+5V INPUT
Q1 T1P42 Q2 2N4403 1k 10
3.3V/ 3.0V @ 4A
Figure 4. Dropout Voltage vs. Load Current of Figure 3
LOAD-TRANSIENT RESPONSE
VOUT +3.3V, 20mV/div
BASE IN C1 220F ON / OFF SHDN GND
BLIM OUT
R2 100k C2 470F x3
MAX688 MAX689
PFO CC C3 10nF
POWER FAIL
IOUT 1A/div
50s/div
Figure 3. 4A Low-Dropout Circuit
Figure 5. Transient Response for a 200mA to 4A Load Step Using Circuit of Figure 3
_______________________________________________________________________________________
9
High-Accuracy, Low-Dropout Linear Regulators MAX687/MAX688/MAX689
Table 2a. Component Suppliers
DEVICE CAPACITORS 267 series Matsuo Surface Mount MANUFACTURER PRODUCTION METHOD
Table 2b. Manufacturers' Phone and Fax Numbers
MANUFACTURER Central Semiconductor Matsuo COUNTRY USA USA USA USA Nichicon Japan USA Sanyo Japan TELEPHONE FAX
(516) 435-1110 (516) 435-1824 (714) 969-2491 (714) 960-6492 (602) 244-3370 (602) 244-4015 (708) 843-7500 (708) 843-2798 +81-7-52318461 +81-7-52564158
F95 Tantalum series Nichicon 595 Tantalum series Sprague OS-CON series low-ESR organic semiconductor LXF series
Motorola Sanyo Through-Hole United Chemi-Con
BIPOLAR TRANSISTORS ZTX749 T1P42 2N4403 2N2907A CMPT2907A PZT2907AT1 FZT749 Zetex Motorola Through-Hole Motorola Motorola Central Semiconductor Motorola Zetex Surface Mount Zetex Sprague United Chemi-Con
(619) 661-6835 (619) 661-1055 +81-7-20706306 +81-7-20701174
USA USA USA UK
(603) 224-1961 (603) 224-1430 (714) 255-9500 (714) 255-9400 (516) 543-7100 (516) 864-7630 +44-61-6275105 +44-61-6275467
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High-Accuracy, Low-Dropout Linear Regulators
_Ordering Information (continued)
PART MAX688CPA MAX688CSA MAX688CUA MAX688EPA MAX688ESA MAX689CPA MAX689CSA MAX689CUA MAX689EPA MAX689ESA TEMP. RANGE 0C to +70C 0C to +70C 0C to +70C -40C to +85C -40C to +85C 0C to +70C 0C to +70C 0C to +70C -40C to +85C -40C to +85C PIN-PACKAGE 8 Plastic DIP 8 SO 8 MAX 8 Plastic DIP 8 SO 8 Plastic DIP 8 SO 8 MAX 8 Plastic DIP 8 SO
MAX687/MAX688/MAX689
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High-Accuracy, Low-Dropout Linear Regulators MAX687/MAX688/MAX689
________________________________________________________Package Information
DIM
C A 0.101mm 0.004 in B A1 L
e
A A1 B C D E e H L
INCHES MAX MIN 0.044 0.036 0.008 0.004 0.014 0.010 0.007 0.005 0.120 0.116 0.120 0.116 0.0256 0.198 0.188 0.026 0.016 6 0
MILLIMETERS MIN MAX 0.91 1.11 0.10 0.20 0.25 0.36 0.13 0.18 2.95 3.05 2.95 3.05 0.65 4.78 5.03 0.41 0.66 0 6
E
H
8-PIN MAX MICROMAX SMALL OUTLINE PACKAGE
D
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.
12 __________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 (408) 737-7600 (c) 1994 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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Price & Availability of MAX688

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