Maxim MAX689CSA, MAX689CUA, MAX689EPA, MAX688CSA, MAX688EPA Datasheet

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19-0329; Rev 0; 12/94

EVALUATION KIT MANUAL

FOLLOWS DATA SHEET

High-Accuracy, Low-Dropout

Linear Regulators

_______________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 (β > 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.

________________________Applications

High-Efficiency Linear Regulator Battery-Powered Devices Portable Instruments Portable Telephones Power Supply or Backup Supply for Memory

__________________Pin Configuration

____________________________Features

♦ Fixed Outputs:

3.3V (MAX687/MAX688)

3.0V (MAX689)

♦ Directly Drives External PNP Transistor ♦ 10mA Min Base-Current Drive for >1A Output ♦ Low Dropout Voltage:

100mV Dropout at 650mA Output (FZT749) 40mV Dropout at 200mA Output (FZT749)

0.8V Dropout at 4A Output

♦ Power-Fail Output Monitors the Output Voltage ♦ Automatic, Latched Shutdown when Output Falls Out

of Regulation (MAX687)

♦ Precision Threshold Shutdown Control

(MAX688/MAX689)

♦ Low Supply Current:

150µA Operating <1µA Shutdown

♦ 2.7V to 11.0V Supply Range ♦ 8-Pin DIP/SO/µMAX Packages ♦ <2mV Line Transient with 3.4V to 3.6V Input ♦ Output Accuracy <±2%

______________Ordering Information

PART

MAX687CPA

MAX687CSA MAX687CUA 0°C to +70°C MAX687EPA MAX687ESA -40°C to +85°C

Ordering Information continued at end of data sheet.

TEMP. RANGE PIN-PACKAGE

0°C to +70°C 0°C to +70°C

-40°C to +85°C 8 Plastic DIP

8 Plastic DIP 8 SO 8 µMAX

8 SO

__________Typical Operating Circuit

+3.5V to +5V INPUT

Q1

FZT749

12Ω



3.3V @ 500mA

MAX687/MAX688/MAX689

TOP VIEW

(ON) SHDN

( ) ARE FOR MAX687

1 2

MAX687 MAX688

PFO

GND

MAX689

DIP/SO/µMAX

________________________________________________________________

BASE

BLIM

OUT

2.2µF

C1

GND

BASE

BLIM

MAX687

GND

Maxim Integrated Products

Call toll free 1-800-998-8800 for free samples or literature.

OUT

PFO

C2

68µF

POWER-FAIL

OUTPUT

C3 10nF

High-Accuracy, Low-Dropout Linear Regulators

ABSOLUTE MAXIMUM RATINGS

Input Supply Voltage IN to GND............................................12V

Terminal Voltages to GND

(MAX687)........................................-0.3V to V

PFO

(MAX688/MAX689) ......................................-0.3V to 12V

PFO

All Remaining Pins .....................................-0.3V to V

Sink Current ...............................................................10mA

PFO

Source Current (MAX687)...........................................10mA

PFO

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.

OUT

+ 0.3V + 0.3V

Continuous Power Dissipation (T

Plastic DIP (derate 9.09mW/°C above +70°C) ............727mW

SO (derate 5.88mW/°C above +70°C).........................471mW

µMAX (derate 4.1mW/°C above +70°C) ......................330mW

Operating Temperature Ranges

MAX68_C_A .......................................................0°C to +70°C

MAX68_E_A ....................................................-40°C to +85°C

Storage Temperature Range.............................-65°C to +165°C

Lead Temperature (soldering, 10sec).............................+300°C

ELECTRICAL CHARACTERISTICS

(VIN= 3.8V, SHDN = VIN(MAX688/MAX689), RB= 0Ω, C1 = 2.2µF, C2 = 10µF, C3 = 10nF, TA= T noted. Typical values are at T

LINEAR REGULATOR

Supply Voltage

MAX687/MAX688/MAX689

Output Voltage

Dropout Voltage (Note 2)

Line Regulation

Supply Current

BASE Sink Current

Base-Current Limit

= +25°C.)

OUT

GND

BASE

CONDITIONS

(Note 1)

MAX687/MAX688

MAX689

PNP = FZT749, I

OUT

MAX687/MAX688

MAX689 1µA ≤ I

VIN= 3.8V, PNP = FZT749, no load

BASE

RBis connected from BASE to BLIM (Ω), RB= 0Ω to 100Ω

(Note 3)

PNP = FZT749, I

≤ 10mA

BASE

= VIN- 1V

= 200mA, C2 = 20µF

LOAD

= 100mA (Note 4)

LOAD

VIN= 3.8V, I

3.8V ≤ VIN≤ 11.0V, 1µA ≤ I

VIN= 3.5V, I

3.5V ≤ VIN≤ 11.0V, 1µA ≤ I

3.8V ≤ VIN≤ 11.0V, I

= 1mA

BASE

3.5V ≤ VIN≤ 11.0V, I

= 1mA

BASE

On Standby,

MAX688/MAX689 Shutdown

BASE

≤ 10mA

BASE

≤ 10mA

= 1mA

= +70°C)

to T

MIN

3.2 3.3 3.4

3.13 3.3 3.47

2.9 3.0 3.1

2.85 3.0 3.15

70 100 130

+ 5Ω RB+ 5Ω RB+ 5Ω

, unless otherwise

MAX

0.4 1.4

150 250

11 25

< 0.02 1

UNITSMIN TYP MAXSYMBOLPARAMETER

V2.7 11.0V

mV40VIN- V

mV/V

mV45 60Load Regulation

µA

mA10 20 40I

µs300Start-Up Time

%2Start-Up Overshoot

µF10C2Load Capacitance

2 _______________________________________________________________________________________

High-Accuracy, Low-Dropout

Linear Regulators

ELECTRICAL CHARACTERISTICS (continued)

(VIN= 3.8V, SHDN = VIN(MAX688/MAX689), RB= 0Ω, C1 = 2.2µF, C2 = 10µF, C3 = 10nF, TA= T noted. Typical values are at T

= +25°C.)

CONDITIONS

MAX687: ON, PFO, SHDN

PFT

NOM

PFT

SD OH OL

- V

IH IL

Falling V

Falling V Falling V

SOURCE

SINK

, comparators monitor V

OUT

, comparators monitor V

OUT

, comparators monitor V

OUT

= 50µA, part on, VIN= 2.7V VV

= 1.2mA, VIN= 2.7V V0.06 0.3V Output turns on Output remains off 0.2V

OUT

PFO Threshold Voltage Below V

(Note 5)

NOM

Shutdown Threshold Voltage Below V

PFT

Shutdown Threshold Voltage PFO Output Voltage High PFO Output Voltage Low

ON Threshold Voltage

MAX688/MAX689: SHDN, PFO

PFO Threshold Voltage

SHDN Threshold Voltages

PFT

SON

SSY

SSD

Falling V parators monitor V

OUT

, com-

On, SHDN falling Standby Shutdown

MAX688

OUT

MAX689 2.77 2.85 2.89

Rising SHDN, standby→on V

= 1.23V nA-25 25SHDN Input Current

SHDN

Glitch immunity I

PFO Output Voltage Low

PFO Off Leakage Current Output Noise Voltage

Note 1: Minimum VINfor regulated V

ence 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 V Note 3: The start-up time specification is the time taken from ON or SHDN

depends on the characteristics of the external PNP transistor, and on the load. The refer-

OUT

- V

and is a function of load capacitance, C2, and load resistance, R

Note 4: Minimum load capacitance is a function of RL. Minimum C2 = 10µF for loads up to 100mA and 1µF/10mA for higher loads.

ESR of C2 should be no larger than 1/100 of R

Note 5: The nominal output voltage, V

, is defined under the default conditions of testing: VIN= 3.8V, I

NOM

= 1.2mA, VIN= 2.7V

SINK

= 11V, V

PFO

10Hz ≤ f ≤ 10kHz, I 10Hz ≤ f ≤ 1MHz, I

when V

OUT

. Guaranteed by design.

> 1.25V

SHDN

= 200mA

LOAD

= 200mA

LOAD

is 50mV below its value at VIN= V

rising to BASE sinking current. V

NOM

to T

, unless otherwise

MAX

OUT

MIN

- 0.3V

1.0V

3.07 3.13 3.19

1.25V

1.0 1.2V

0.2V

105

+ 1V.

rise time is longer

OUT

= 1mA, TA= T

BASE

MIN

UNITSMIN TYP MAXSYMBOLPARAMETER

µV

to T

MAX687/MAX688/MAX689

mV110 170 mV7PFO Hysteresis mV20 70V

V2.96V

nA0.2 100ON Input Leakage Current

mV7PFO Hysteresis

mV70SHDN Hysteresis

µs100PFO, SHDN Transient Rejection

V0.06 0.3V

µA1

RMS

MAX

_______________________________________________________________________________________ 3

High-Accuracy, Low-Dropout Linear Regulators

__________________________________________Typical Operating Characteristics

(Circuits of Figures 1 and 2, VIN= 5V, Q1 = FZT749, TA = +25°C, unless otherwise noted.)

MAX689

50 100 250200150

NUMBER OF UNITS

OUTPUT VOLTAGE DISTRIBUTION

3.32289

3.31932

3.31576

3.31219

3.30862

3.30505

3.30149

3.29792

OUTPUT VOLTAGE (V)

3.29435

3.29078

3.28722

3.28365

0 50 100 250200150

MAX687

NUMBER OF UNITS

3.32145

3.31920

3.31696

MAX687/9-02

3.31472

3.31248

3.31024

3.30800

3.30576

3.30352

3.30128

3.29904

OUTPUT VOLTAGE (V)

3.29679

3.29455

3.29231

3.29007

3.28783

OUTPUT VOLTAGE DISTRIBUTION

MAX688

0 50 100

NUMBER OF UNITS

MAX687/9-01

250200150

OUTPUT VOLTAGE DISTRIBUTION

3.01595

3.01420

3.01245

3.01071

3.00896

3.00721

3.00547

3.00372

3.00198

3.00023

OUTPUT VOLTAGE (V)

2.99848

2.99674

2.99499

2.99324

2.99150

2.98975

MAX687/9-03

DROPOUT VOLTAGE 

0.30

vs. LOAD CURRENT

Q1 = FZT749 RB = 0Ω

0.25

MAX687/MAX688/MAX689

0.20

(V)

OUT

0.15

- V

0.10

0.05

0 200 600 1000 1400 1800

OBSERVE MAXIMUM POWER DISSIPATION LIMIT OF  EXTERNAL PASS TRANSISTOR.

MAX687/9-05

1.0

0.9

0.8

0.7

(V)

0.6

OUT

0.5

- V

0.4

0.3

0.2

0.1 0

LOAD CURRENT (mA)

GND CURRENT vs. DROPOUT VOLTAGE

7 6

GND CURRENT (mA)

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0

300mA LOAD

100mA LOAD

VIN - V

OUT

10mA LOAD

(V)

MAX687/9-7

GND CURRENT (mA)

7 6

DROPOUT VOLTAGE

vs. LOAD CURRENT

Q1 = 2N2907 RB = 0Ω

0 200 600 1000

400 800

LOAD CURRENT (mA)

GND CURRENT vs. DROPOUT VOLTAGE

300mA LOAD

100mA LOAD

0812345 76

VIN - V

OUT

10mA LOAD

(V)

GND CURRENT 

vs. LOAD CURRENT

MAX687/9-5

GND CURRENT (mA)

0 200 400 600 800 1000 1200

LOAD CURRENT (mA)

NO-LOAD SUPPLY CURRENT 

vs. TEMPERATURE

146 144

MAX687/9-8

142 140 138 136 134 132

SUPPLY CURRENT (µA)

130 128 126

-55 -25 0 25 50 75 100 125 TEMPERATURE (°C)

MAX687/9-06

MAX687/9-9

4 _______________________________________________________________________________________

High-Accuracy, Low-Dropout

Linear Regulators

____________________________Typical Operating Characteristics (continued)

(Circuits of Figures 1 and 2, VIN= 5V, Q1 = FZT749, TA = +25°C, unless otherwise noted.)

SHUTDOWN SUPPLY CURRENT 

vs. TEMPERATURE

-55 -25 0 25 50 75 100 125 TEMPERATURE (°C)

SHUTDOWN SUPPLY CURRENT (µA)

0.3000

0.2500

0.2000

0.1500

0.1000

0.0500

LINE-TRANSIENT RESPONSE

= 70mA

LOAD

C1 = 2.2µF C2 = 20µF C3 = 10nF

2ms/div

LOAD-TRANSIENT RESPONSE

OUT

3.3V 1mV/div

IN

3.6V

IN

3.4V

3.315

MAX687/9-10

3.310

3.305

3.300

3.295

OUTPUT VOLTAGE (V)

3.290

3.285

3.280

-55 -25 0 25 50 75 100 125

= 200mA

LOAD

C1 = 2.2µF C2 = 20µF C3 = 10nF

OUTPUT VOLTAGE 

vs. TEMPERATURE

TEMPERATURE (°C)

LINE-TRANSIENT RESPONSE

2ms/div

RIPPLE REJECTION vs. FREQUENCY

80 70

MAX687/9-11

= 3.6V Min

= 200mA

LOAD

40 30

RIPPLE REJECTION (dB)

20 10

C2 = 20µF

10 100 1k 10k 100k

POWER-UP AND EXIT FROM SHUTDOWN

OUT

3.3V 1mV/div

IN

3.6V V

IN

3.4V

= 500mA

LOAD

C1 = 2.2µF C2 = 68µF C3 = 10nF

LOAD-TRANSIENT RESPONSE

MAX687/MAX688

= 4.3V Min

= 20mA

LOAD



FREQUENCY (Hz)



MAX687/MAX688



1ms/div

MAX687/MAX688/MAX689

MAX687/9-16

IN

5V/div

OUT

1V/div

SHDN 5V/div

OUT

3.3V 10mV/div

500mA



LOAD

200mA/div

0mA

VIN = 3.4V

100µs/div

= 3.5V

100µs/div

_______________________________________________________________________________________

OUT

3.3V 10mV/div

500mA

LOAD

200mA/div

0mA



High-Accuracy, Low-Dropout Linear Regulators

______________________________________________________________Pin Description

NAME FUNCTION

1 IN Positive input voltage, 2.7V to 11.0V

(MAX687)

SHDN

(MAX688/

MAX689)

3 PFO

4 GND Ground 5 OUT Regulator Output. MAX687/MAX688, 3.3V; MAX689, 3.0V.

6 BLIM

MAX687/MAX688/MAX689

7 BASE 8 CC Compensation Capacitor. Connect a non-polarized capacitor (10nF to 100nF) from CC to GND.

ON activates the regulator when pulsed high. In order for the regulator to remain on, ON must remain high until V 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 VINif not used.

SHDN is a three-level input that controls the mode of operation. The device is on when V The output is disabled and the supply current is reduced (IIN< 25µA, standby mode) when V and is fully off (IIN< 1µA, shutdown mode) when V tion is not used. PFO is low when SHDN is low (below 0.2V).

Power-Fail Output. PFO trips when V 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.

Base current limit. A resistor (RB) connected between BASE and BLIM sets the maximum base drive to the PNP transistor: I vides 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.

exceeds the internal shutdown threshold voltage. The MAX687 is shut down when V

OUT

< 0.2V. Connect SHDN to IN if the shutdown func-

SHDN

is 170mV below nominal V

OUT

≤ 0.1V / (RB + 5Ω). This limits quiescent current rise during dropout and also pro-

BASE

OUT

at I

= 1mA. PFO sources and

BASE

SHDN

OUT

> 1.25V.

SHDN

< 2.96V,

< 1.2V,

_______________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 V 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).

6 _______________________________________________________________________________________

. The Power-Fail Output (PFO) goes low when

CE(SAT)

Table 1. Device Functions

FUNCTION MAX687 MAX688 MAX689

OUT

Shutdown

Control

PFO Sources & Sinks Open Drain Open Drain

The MAX687’s output voltage is internally monitored; a falling V

OUT

put 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 V by 2.96V. PFO is guaranteed to trip before the device

3.3V 3.3V 3.0V

Automatic at low

. Latched.

OUT

Use ON to start.

External

SHDN

is signaled by PFO going low. As the out-

, and shutdown occurs

OUT

External

SHDN

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 (0.1µF and 10kΩ) 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 (I

> 3A), increase the value

LOAD

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 (<25µA). 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 V

is less than 1.2V,

SHDN

the output is off. The device is fully shut down (<1µA) 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= 12Ω, BLIM limits base current to 6mA (I

Current Limiting

= 0.1V / (RB+ 5Ω)). See

BASE

section.

Base-

The PFO comparators on all three devices, and the internal shutdown comparator on the MAX687, reject high-speed spikes (<100µs). This reduces the PFOoutput’s noise sensitivity, and stops the MAX687 from being shut down inadvertently when there is noise on the input supply.

_______________Transistor Selection

The PNP pass transistor must meet specifications for

• current gain,

• power dissipation, and

• collector current.

The hFEinfluences the maximum output current the circuit can deliver. The largest guaranteed output current

Specifications

MAX687/MAX688/MAX689

+5V INPUT

C4

0.1µF

2.2µF

GND

ON CAN BE DRIVEN DIRECTLY FROM LOGIC WHEN R1 AND C4 ARE NOT USED.

Figure 1. MAX687 Operating Circuit

Q1 FZT749

12Ω

MAX687

GND

BLIM

OUT

PFO

BASE

C1

R1 10kΩ

_______________________________________________________________________________________ 7

68µF

C2

C3 10nF

3.3V @ 500mA

POWER FAIL

12Ω

3.3V/ 3.0V @ 500mA

BLIM

OUT

PFO

C3 10nF

+5V INPUT

2.2µF

ON / OFF

GND

Figure 2. MAX688/MAX689 Operating Circuit

Q1 FZT749

BASE

C1

SHDN

MAX688 MAX689

GND

C2 68µF

POWER FAIL

R2 100k

High-Accuracy, Low-Dropout Linear Regulators

is given by I sistor’s rated power dissipation must exceed the actual power dissipated in the transistor. The power dissipated (PD) equals the maximum load current (I times the maximum input to output voltage differential: PD = I sistor collector current must exceed the maximum load current. Suitable transistors include the Zetex FZT749, and the 2N2907A (see Table 2).

LOAD(MAX)

x (V

IN(MAX)

= 10mA x h

- V

OUT

. The tran-

FE(MIN)

LOAD(MAX)

). The rated tran-

)

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 5Ω resistor in series with the external resistance. Choose the base-current-limiting resistor, RB, so the drop across it at rated load is approximately 50mV.

mV x h

()

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+ 5Ω, base-current drive

MAX687/MAX688/MAX689

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 hFEis defined within reasonable limits, base-current control effectively limits output current without a dropout voltage penalty.

FE(MIN)

LOAD(MAX)

−Ω505

________________Capacitor Selection

Connect a bypass capacitor from IN to GND. 4.7µF makes the circuit insensitive to layout, and is sufficient for any load. Smaller values may be used—down to

0.33µF—with low-ESR capacitors, good board layout, and a low-impedance incoming supply.

Bypass Capacitor (C1)

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 10µF. For currents above 100mA, use 1µF of capacitance for every 10mA of load current (e.g., 20µF for 200mA load, 50µF 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 0°C.

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.

__________________Power-Fail Output

The PFO output trips when V nal V rent 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.

OUT

at I

= 1mA. PFO sources and sinks cur-

BASE

is 170mV below nomi-

OUT

8 _______________________________________________________________________________________

High-Accuracy, Low-Dropout

Linear Regulators

__________Applications Information

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- V maintain regulation for different load currents. Figure 5 shows an oscilloscope plot of the transient response of a 200mA to 4A load step.

+5V INPUT

C1 220µF

ON / OFF

High-Power Output Circuit

) voltage required to

OUT

Q1

T1P42

Q2

2N4403

10Ω1kΩ

MAX688 MAX689

BLIM

OUT

PFO

C3 10nF

BASE

SHDN

GND

3.3V/ 3.0V @ 4A

C2 470µF x3

POWER FAIL

R2 100kΩ

DROPOUT VOLTAGE vs. LOAD CURRENT

1.0 Q1 = TIP42

0.9

Q2 = 2N4403 BASE = BLIM

0.8

0.7

(V)

0.6

OUT

0.5

- V

0.4

0.3

0.2

0.1

0 40001000 2000 3000

LOAD CURRENT (mA)

MAX687/9-04

Figure 4. Dropout Voltage vs. Load Current of Figure 3

LOAD-TRANSIENT RESPONSE

50µs/div



OUT

+3.3V, 20mV/div

OUT

1A/div

MAX687/MAX688/MAX689

Figure 3. 4A Low-Dropout Circuit

_______________________________________________________________________________________ 9

Figure 5. Transient Response for a 200mA to 4A Load Step Using Circuit of Figure 3

High-Accuracy, Low-Dropout Linear Regulators

Table 2a. Component Suppliers

DEVICE MANUFACTURER

CAPACITORS

267 series Matsuo

595 Tantalum series Sprague OS-CON series

low-ESR organic semiconductor

LXF series United Chemi-Con

BIPOLAR TRANSISTORS

ZTX749 Zetex T1P42 Motorola 2N4403 Motorola 2N2907A Motorola CMPT2907A Central Semiconductor PZT2907AT1 Motorola

MAX687/MAX688/MAX689

FZT749 Zetex

Sanyo

PRODUCTION

METHOD

Surface MountF95 Tantalum series Nichicon

Through-Hole

Surface Mount

Table 2b. Manufacturers’ Phone and Fax Numbers

MANU-

FACTURER

Central Semiconductor

Matsuo USA (714) 969-2491 (714) 960-6492 Motorola USA (602) 244-3370 (602) 244-4015

Nichicon

Sanyo

Sprague USA (603) 224-1961 (603) 224-1430 United

Chemi-Con

Zetex

COUNTRY TELEPHONE FAX

USA (516) 435-1110 (516) 435-1824

USA (708) 843-7500 (708) 843-2798

Japan

USA (619) 661-6835 (619) 661-1055

Japan

USA (714) 255-9500 (714) 255-9400

USA (516) 543-7100 (516) 864-7630

+81-7-5231-

8461

+81-7-2070-

6306

+44-61-627-

5105

+81-7-5256-

4158

+81-7-2070-

1174

+44-61-627-

5467

10 ______________________________________________________________________________________

High-Accuracy, Low-Dropout

Linear Regulators

_Ordering Information (continued)

PART

MAX688CPA

MAX688CSA MAX688CUA 0°C to +70°C MAX688EPA MAX688ESA -40°C to +85°C MAX689CPA MAX689CSA MAX689CUA 0°C to +70°C MAX689EPA MAX689ESA -40°C to +85°C

TEMP. RANGE PIN-PACKAGE

0°C to +70°C 0°C to +70°C

-40°C to +85°C 8 Plastic DIP

0°C to +70°C 8 Plastic DIP 0°C to +70°C

-40°C to +85°C 8 Plastic DIP

8 Plastic DIP 8 SO 8 µMAX

8 SO

8 SO 8 µMAX

8 SO

MAX687/MAX688/MAX689

______________________________________________________________________________________ 11

High-Accuracy, Low-Dropout Linear Regulators

________________________________________________________Package Information

INCHES MILLIMETERS

DIM

0.101mm

0.004 in

A1B

E H

8-PIN µMAX

MICROMAX SMALL OUTLINE

MAX687/MAX688/MAX689

PACKAGE



A

A1

B C D E

e

H

L

MIN

0.036

0.004

0.010

0.005

0.116

0.188

0.016 0°

MAX

MIN

0.044

0.91

0.008

0.10

0.014

0.25

0.007

0.13

0.120

2.95

0.120

2.95



0.198

0.026 6°



4.78

0.41 0°

MAX

1.11

0.20

0.36

0.18

3.05

0.650.0256



5.03

0.66 6°

Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are

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.

implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.

__________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 (408) 737-7600

Maxim MAX689CSA, MAX689CUA, MAX689EPA, MAX688CSA, MAX688EPA Datasheet

Specifications and Main Features

Frequently Asked Questions

User Manual