MAX1637
Miniature, Low-Voltage,
Precision Step-Down Controller
6 _______________________________________________________________________________________
____________________________________Typical Operating Characteristics (continued)
(V
OUT
= 3.3V, T
A
= +25°C, unless otherwise noted.)
______________________________________________________________Pin Description
PIN
High-Side Current-Sense InputCSH1
FUNCTIONNAME
Low-Side Current-Sense InputCSL2
Compensation Pin. Connect a small capacitor to GND to set the integration time constant.CC4
Feedback Input. Connect to center of resistor divider.FB3
Shutdown Control Input. Turns off entire IC. When low, reduces supply current below 0.5µA (typ). Drive with
logic input or connect to RC network between GND and V
CC
for automatic start-up.
SHDN
6
Analog GroundGND8
Oscillator Frequency Select and Synchronization Input. Tie to V
CC
for 300kHz operation; tie to GND for
200kHz operation.
SYNC7
1.100V Reference Output. Capable of sourcing 50µA for external loads. Bypass with 0.22µF minimum.REF5
Gate-Drive and Boost-Circuit Power Supply. Can be driven from a supply other than V
CC
. If the same supply
is used by both V
CC
and V
GG
, isolate V
CC
from V
GG
with a 20Ω resistor. Bypass to PGND with a 4.7µF
capacitor. V
GG
current = (Q
G1
+ Q
G2
) x f, where Q
G
is the MOSFET gate charge at V
GS
= V
GG
.
V
GG
10
Power GroundPGND12
Low-Side Gate-Driver OutputDL11
High-Side Gate-Driver OutputDH14
Low-Noise Mode Control. Forces fixed-frequency PWM operation when high.
SKIP
16
Inductor ConnectionLX15
Boost Capacitor ConnectionBST13
Main Analog Supply-Voltage Input to the Chip. V
CC
powers the PWM controller, logic, and reference. Input
range is 3.15V to 5.5V. Bypass to GND with a 0.1µF capacitor close to the pin.
V
CC
9
