MAX8869 MAXIM [Maxim Integrated Products], MAX8869 Datasheet - Page 7

• Manufacturer Part Number: MAX8869
• Description: 1A, Microcap, Low-Dropout, Linear Regulator Foldback Output Current Limit
• Manufacturer: MAXIM [Maxim Integrated Products]

Figure 1. Functional Diagram
Figure 2. Typical Operating Circuit with Preset Output Voltage
The MAX8869 features Dual Mode operation. Connect
SET to GND (Figure 2) for preset voltage mode (see
Ordering Information ). In adjustable mode, set the out-
put between +0.8V to +5.0V through two external resis-
tors connected as a voltage-divider to SET (Figure 3).
The output voltage is set by the following equation:
V
IN
1µF
ON
C
IN
SHDN
GND
C
OFF
SS
SS
IN
V
OUT
_______________________________________________________________________________________
IN
IN
IN
IN
SHDN
SS
= V
Output Voltage Selection
6μA
SET
SHUTDOWN
REFERENCE
MAX8869
LOGIC
0.8V
GND
OUT
OUT
OUT
OUT
RST
SET
(1 + R1 / R2)
V
SS
MAX8869
ERROR AMP
C
1µF
OUT
RESET
OUTPUT
1A, Microcap, Low-Dropout,
SHUTDOWN
736mV
COMPARATOR
V
DUAL MODE
OUT
where V
Since the input bias current at SET is nominally 50nA,
large resistance values can be used for R1 and R2 to
minimize power consumption without losing efficiency.
Up to 80kΩ is acceptable for R2.
In preset voltage mode, the impedance between SET
and ground should be less than 10kΩ. Otherwise, spu-
rious conditions could cause the voltage at SET to
exceed the 80mV Dual Mode threshold.
A logic low on SHDN disables the MAX8869. In shut-
down, the pass transistor, control circuitry, reference,
and all biases are turned off, reducing supply current to
typically 0.1µA. Connect SHDN to IN for normal opera-
tion. In shutdown, RST is low and the soft-start capaci-
tor is discharged.
The MAX8869 features a low V
asserts when the output voltage falls out of regulation.
The open-drain RST goes low when OUT falls 8%
DETECTOR
92% V
WITH FOLDBACK
MOSFET DRIVER
CURRENT LIMIT
V
80mV
SS
OUT
3ms
SET
= +0.8V. To simplify resistor selection:
IN
DELAY TIMER
Linear Regulator
R1 = R2 (V
THERMAL
SENSOR
OUT
OUT
/ V
NMOS
SET
RST Comparator
OUT
PMOS
R1
R2
- 1)
indicator that
Shutdown
OUT
RST
SET
7