The ISL6237 dual step-down, switch-mode power-supply
(SMPS) controller generates logic-supply voltages in
battery-powered systems. The ISL6237 includes two
pulse-width modulation (PWM) controllers, 5V/3.3V and
1.5V/1.05V. The output of SMPS1 can also be adjusted from
0.7V to 5.5V. The SMPS2 output can be adjusted from 0.5V to
2.5V by setting REFIN2 voltage. This device features a linear
regulator providing 3.3V/5V, or adjustable from 0.7V to 4.5V
output via LDOREFIN. The linear regulator provides up to
100mA output current with automatic linear-regulator
bootstrapping to the BYP input. When in switchover, the LDO
output can source up to 200mA. The ISL6237 includes
on-board power-up sequencing, power-good (POK_) outputs,
digital soft-start, and internal soft-stop output discharge that
prevents negative voltages on shutdown.
Constant on-time PWM control scheme operates without
sense resistors and provides 100ns response to load
transients while maintaining a relatively constant switching
frequency. The unique ultrasonic pulse-skipping mode
maintains the switching frequency above 25kHz, which
eliminates noise in audio applications. Other features include
pulse skipping, which maximizes efficiency in light-load
applications, and fixed-frequency PWM mode, which reduces
RF interference in sensitive applications.