Datasheet

MAX8576–MAX8579
3V to 28V Input, Low-Cost, Hysteretic
Synchronous Step-Down Controllers
8 _______________________________________________________________________________________
PIN
MAX8576/
MAX8577
MAX8578/
MAX8579
NAME
FUNCTION
11FB
Feedback Input. Regulates at V
FB
= 0.59V. Connect FB to a resistor-divider to set the output
voltage. See the Setting the Output Voltage section.
22S S
S oft- S tar t. U se an exter nal cap aci tor ( C
SS
) to ad j ust the soft- star t ti m e. An i nter nal 80kΩ r esi stor g i ves
ap p r oxi m atel y 4m s soft- star t ti m e for a 0.01µF exter nal cap aci tor . An i nter nal 250nA cur r ent si nk i n
hi ccup m od e g i ves ap p r oxi m atel y 10% d uty cycl e d ur i ng faul t cond i ti ons.
3—VL
Internal 5V Linear-Regulator Output. Bypass with a 4.7µF or larger ceramic capacitor. Must be
connected to IN for operation from a 3.3V to 5.5V input.
—3V
CC
Supply Input (3V to 5.5V). Bypass with a 4.7µF or larger ceramic capacitor to GND.
4 4 GND Ground
5 5 DL Low-Side Gate-Drive Output. Drives the synchronous-rectifier MOSFET.
6 6 BST
Boost-Capacitor Connection for High-Side Gate-Drive Output. Connect a 0.1µF ceramic
capacitor from BST to LX and a Schottky or switching diode and a 4.7Ω series resistor from
BST to VL (MAX8576/MAX8577) or V
CC
(MAX8578/MAX8579). See Figure 4.
7 7 LX External Inductor Connection. Connect LX to the junctions of the MOSFETs and inductor.
8 8 DH High-Side Gate-Drive Output. Drives the high-side MOSFET.
9—IN
Supply Voltage Input of the Internal Linear Regulator (3V to 28V). Connect to VL for operation
from 3V to 5.5V input. Connect a 0.47µF or larger ceramic capacitor from IN to GND.
—9EN
Enable Input. A logic low on EN shuts down the converter and discharges the soft-start
capacitor. Drive high or connect to V
CC
for normal operation.
10 10
OCSET
Overcurrent-Limit Set. Programs the high-side peak current-limit threshold by setting the
maximum-allowed V
DS
voltage drop across the high-side MOSFET. Connect a resistor from IN
to OCSET; an internal 50µA current sink sets the maximum voltage drop relative to V
IN
. See the
Setting the Current Limit section.
Pin Description