19-0329; Rev 0; 12/94
UAL
IT MAN
TION K
A
EET
EVALU
ATA SH
OWS D
FOLL
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:
150µA Operating
<1µA Shutdown
o
2.7V to 11.0V Supply Range
o
8-Pin DIP/SO/µMAX 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 regula-
tors operate with an input-to-output voltage differential lim-
ited 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 tran-
sistors (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 pro-
vides 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 applica-
tions include portable telephones and other battery-pow-
ered 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 shut-
down-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, per-
mitting 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
0°C to +70°C
0°C to +70°C
0°C to +70°C
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
8 Plastic DIP
8 SO
8 µMAX
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
R
B
12Ω
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
2.2µF
ON
ON
7
6
5
BASE
BLIM
OUT
C2
68µF
PFO
CC
GND
C3
10nF
POWER-FAIL
OUTPUT
MAX687
MAX688
MAX689
MAX687
DIP/SO/µMAX
________________________________________________________________
Maxim Integrated Products
1
Call toll free 1-800-998-8800 for free samples or literature.
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 V
OUT
+ 0.3V
PFO (MAX688/MAX689) ......................................-0.3V to 12V
All Remaining Pins .....................................-0.3V to V
IN
+ 0.3V
PFO Sink Current ...............................................................10mA
PFO Source Current (MAX687)...........................................10mA
Continuous Power Dissipation (T
A
= +70°C)
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
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
(V
IN
= 3.8V, SHDN = V
IN
(MAX688/MAX689), R
B
= 0Ω, C1 = 2.2µF, C2 = 10µF, C3 = 10nF, T
A
= T
MIN
to T
MAX
, unless otherwise
noted. Typical values are at T
A
= +25°C.)
PARAMETER
LINEAR REGULATOR
Supply Voltage
V
IN
(Note 1)
V
IN
= 3.8V, I
BASE
= 1mA
MAX687/MAX688
Output Voltage
V
OUT
MAX689
Dropout Voltage (Note 2)
3.8V
≤
V
IN
≤
11.0V,
1µA
≤
I
BASE
≤
10mA
V
IN
= 3.5V, I
BASE
= 1mA
3.5V
≤
V
IN
≤
11.0V,
1µA
≤
I
BASE
≤
10mA
3.8V
≤
V
IN
≤
11.0V,
I
BASE
= 1mA
3.5V
≤
V
IN
≤
11.0V,
I
BASE
= 1mA
On
Supply Current
I
GND
V
IN
= 3.8V,
PNP = FZT749,
no load
V
BASE
= V
IN
- 1V
R
B
is connected from BASE to BLIM (Ω),
R
B
= 0Ω to 100Ω
(Note 3)
C2
PNP = FZT749, I
LOAD
= 100mA (Note 4)
10
Standby,
MAX688/MAX689
Shutdown
BASE Sink Current
Base-Current Limit
Start-Up Time
Start-Up Overshoot
Load Capacitance
I
BASE
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
µs
%
µF
µA
mV
11.0
3.4
3.47
3.1
3.15
mV
V
V
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
V
IN
- V
OUT
PNP = FZT749, I
LOAD
= 200mA, C2 = 20µF
MAX687/MAX688
Line Regulation
MAX689
Load Regulation
1µA
≤
I
BASE
≤
10mA
70
100
130
R
B
+ 5Ω R
B
+ 5Ω R
B
+ 5Ω
300
2
2
_______________________________________________________________________________________
High-Accuracy, Low-Dropout
Linear Regulators
ELECTRICAL CHARACTERISTICS (continued)
(V
IN
= 3.8V, SHDN = V
IN
(MAX688/MAX689), R
B
= 0Ω, C1 = 2.2µF, C2 = 10µF, C3 = 10nF, T
A
= T
MIN
to T
MAX
, unless otherwise
noted. Typical values are at T
A
= +25°C.)
PARAMETER
MAX687: ON, PFO, SHDN
PFO Threshold Voltage Below
V
NOM
(Note 5)
PFO Hysteresis
Shutdown Threshold Voltage
Below V
PFT
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
V
SON
SHDN Threshold Voltages
SHDN Hysteresis
SHDN Input Current
PFO, SHDN Transient Rejection
PFO Output Voltage Low
PFO Off Leakage Current
Output Noise Voltage
e
n
V
OL
V
SSY
V
SSD
On, SHDN falling
Standby
Shutdown
Rising SHDN, standby→on
V
SHDN
= 1.23V
Glitch immunity
I
SINK
= 1.2mA, V
IN
= 2.7V
V
PFO
= 11V, V
SHDN
> 1.25V
10Hz
≤
f
≤
10kHz, I
LOAD
= 200mA
10Hz
≤
f
≤
1MHz, I
LOAD
= 200mA
66
105
-25
100
0.06
0.3
1
70
25
1.25
1.0
1.2
0.2
mV
nA
µs
V
µA
µV
RMS
V
V
PFT
Falling V
OUT
, com-
parators monitor V
OUT
MAX688
MAX689
3.07
2.77
3.13
2.85
7
3.19
2.89
V
mV
V
PFT
- V
SD
Falling V
OUT
, comparators monitor V
OUT
V
SD
V
OH
V
OL
V
IH
V
IL
Falling V
OUT
, comparators monitor V
OUT
I
SOURCE
= 50µA, part on, V
IN
= 2.7V
I
SINK
= 1.2mA, V
IN
= 2.7V
Output turns on
Output remains off
0.2
1.0
0.2
100
20
2.96
V
OUT
- 0.3
0.06
0.3
V
NOM
-
V
PFT
Falling V
OUT
, comparators monitor V
OUT
110
170
7
70
mV
mV
mV
V
V
V
V
nA
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
MAX687/MAX688/MAX689
Note 1:
Minimum V
IN
for regulated V
OUT
depends on the characteristics of the external PNP transistor, and on the load. The refer-
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
IN
- V
OUT
when V
OUT
is 50mV below its value at V
IN
= V
NOM
+ 1V.
Note 3:
The start-up time specification is the time taken from ON or SHDN rising to BASE sinking current. V
OUT
rise time is longer
and is a function of load capacitance, C2, and load resistance, R
L
.
Note 4:
Minimum load capacitance is a function of R
L
. 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
L
. Guaranteed by design.
Note 5:
The nominal output voltage, V
NOM
, is defined under the default conditions of testing: V
IN
= 3.8V, I
BASE
= 1mA, T
A
= T
MIN
to T
MAX
.
_______________________________________________________________________________________
3
High-Accuracy, Low-Dropout
Linear Regulators
MAX687/MAX688/MAX689
__________________________________________Typical Operating Characteristics
(Circuits of Figures 1 and 2, V
IN
= 5V, Q1 = FZT749, T
A
= +25°C, unless otherwise noted.)
MAX687
OUTPUT VOLTAGE DISTRIBUTION
MAX687/9-02
MAX688
OUTPUT VOLTAGE DISTRIBUTION
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
MAX687/9-01
MAX689
OUTPUT VOLTAGE DISTRIBUTION
3.01595
3.01420
3.01245
MAX687/9-03
3.32289
3.31932
3.31576
3.32145
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
R
B
= 0Ω
1.0
0.9
0.8
Q1 = 2N2907
R
B
= 0Ω
6
5
GND CURRENT (mA)
4
3
2
1
0
0.7
V
IN
- V
OUT
(V)
0.6
0.5
0.4
0.3
0.2
0.1
0
1800
0
200
400
600
800
1000
LOAD CURRENT (mA)
V
IN
- V
OUT
(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 (µA)
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
V
IN
- V
OUT
(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
V
IN
- V
OUT
(V)
4
_______________________________________________________________________________________
High-Accuracy, Low-Dropout
Linear Regulators
____________________________Typical Operating Characteristics (continued)
(Circuits of Figures 1 and 2, V
IN
= 5V, Q1 = FZT749, T
A
= +25°C, 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 = 20µF
0
V
IN
= 3.6V Min
I
LOAD
= 200mA
V
IN
= 4.3V Min
I
LOAD
= 20mA
MAX687/9-16
0.3000
SHUTDOWN SUPPLY CURRENT (µA)
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
V
OUT
3.3V
1mV/div
V
OUT
3.3V
1mV/div
V
IN
5V/div
V
IN
3.6V
V
IN
3.4V
I
LOAD
= 70mA
C1 = 2.2µF
C2 = 20µF
C3 = 10nF
2ms/div
I
LOAD
= 200mA
C1 = 2.2µF
C2 = 20µF
C3 = 10nF
2ms/div
V
IN
3.6V
V
IN
3.4V
1ms/div
V
OUT
1V/div
SHDN
5V/div
I
LOAD
= 500mA
C1 = 2.2µF
C2 = 68µF
C3 = 10nF
LOAD-TRANSIENT RESPONSE
LOAD-TRANSIENT RESPONSE
V
OUT
3.3V
10mV/div
V
OUT
3.3V
10mV/div
500mA
I
LOAD
200mA/div
0mA
100µs/div
100µs/div
500mA
I
LOAD
200mA/div
0mA
V
IN
= 3.4V
V
IN
= 3.5V
_______________________________________________________________________________________
5
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