MAX1692 Datasheet, PDF (6/12 Pages) Maxim Integrated Products – Low-Noise, 5.5V-Input, PWM Step-Down Regulator

Low-Noise, 5.5V-Input,
PWM Step-Down Regulator
Pin Description
PIN NAME
FUNCTION
1
IN
Supply Voltage Input. Input range from +2.7V to +5.5V. Bypass with a 10µF capacitor.
2
BP
Supply Bypass Pin. Internally connected to IN. Bypass with a 0.1µF capacitor. Do not connect to an
external power source other than IN.
3
GND Ground
4
REF
1.25V, 1.2% Reference Output. Capable of delivering 50µA to external loads. Bypass with a 0.22µF capaci-
tor to GND.
5
FB
Feedback Input
6
LIM
Current-Limit Select Input. Connect LIM to GND for 0.6A current limit or LIM to IN for 1.2A current limit.
Oscillator Sync and Low-Noise, Mode-Control Input.
7
SYNC/
PWM
SYNC/PWM = IN (Forced PWM Mode)
SYNC/PWM = GND (PWM/PFM Mode)
An external clock signal connected to this pin allows for LX switching synchronization.
8
SHDN
Active-Low, Shutdown-Control Input. Reduces quiescent current to 0.1µA. In shutdown, output becomes
high impedance.
9
LX
Inductor Connection to the Drains of the Internal Power MOSFETs
10
PGND Power Ground
SHDN
REF
GND
SYNC/
PWM
FB
PFM CURRENT COMPARATOR
CHIP
BP
SUPPLY
10Ω
MAX1692
REF
12mV
120mV
IN
1Ω
P
LIM COMPARATOR
0.1X
LX
SENSE FET
RAMP
GEN
SYNC
SLOPE COMPENSATION
CELL
FB
PWM
REF
PWM
COMPARATOR
CONTROL AND
DRIVER LOGIC
PWM ON
SIGNAL
40mV
FB
OONN
REF
PFM
REF
COMPARATOR
OVERVOLTAGE
COMPARATOR
NEGLIM
COMPARATOR
5mV IN PFM
ADJ. IN PWM
SENSE FET
0.1X
N
1Ω
PGND
Figure 1. Simplified Functional Diagram
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