MAX1953/MAX1954/MAX1957
Low-Cost, High-Frequency, Current-Mode PWM
Buck Controller
8 _______________________________________________________________________________________
Pin Description
PIN
MAX1953 MAX1954 MAX1957
NAME FUNCTION
1
—
—
ILIM
ILIM Sets the Current-Limit Threshold for the Low-Side N-Channel
MOSFET, as well as the Current-Sense Amplifier Gain. Connect to IN
for 320mV, leave floating for 210mV, or connect to GND for 105mV
current-limit threshold.
—
1
—
HSD
HSD Senses the Voltage at the Drain of the High-Side N-Channel
MOSFET. Connect to the high-side MOSFET drain using a Kelvin
connection.
—
—
1
REFIN
REFIN Sets the FB Regulation Voltage. Drive REFIN with the desired
FB regulation voltage using an external resistor-divider. Bypass to
GND with a 0.1µF capacitor.
2
2
2
COMP
Compensation and Shutdown Control Pin. Connect an RC network to
compensate control loop. Drive to GND to shut down the IC.
3
3
3
FB
Feedback Input. Regulates at V
FB
= 0.8V (MAX1953/MAX1954) or
REFIN (MAX1957). Connect FB to a resistor-divider to set the output
voltage (MAX1953/MAX1954). Connect to output through a decoupling
resistor (MAX1957).
4
4
4
GND
Ground
5
5
5
IN
Input Voltage (3V to 5.5V). Provides power for the IC. For the
MAX1953/MAX1957, IN serves as the current-sense input for the high-
side MOSFET. Connect to the drain of the high-side MOSFET
(MAX1953/MAX1957). Bypass IN to GND close to the IC with a
0.22µF (MAX1954) capacitor. Bypass IN to GND close to the IC with
10µF and 4.7µF in parallel (MAX1953/MAX1957) capacitors. Use
ceramic capacitors.
6
6
6
DL
Low - S i d e G ate- D r i ve Outp ut. D r i ves the synchr onous- r ecti fi er M O S FE T.
S w i ng s fr om P GN D to V
IN
.
7
7
7
PGND
Power Ground. Connect to source of the synchronous rectifier close to
the IC.
8
8
8
DH
High-Side Gate-Drive Output. Drives the high-side MOSFET. DH is a
floating driver output that swings from V
LX
to V
BST
.
9
9
9
LX
Master Controller Current-Sense Input. Connect LX to the junction of
the MOSFETs and inductor. LX is the reference point for the current
limit.
10
10
10
BST
Boost Capacitor Connection for High-Side Gate Driver. Connect a
0.1µF ceramic capacitor from BST to LX and a Schottky diode to IN.
