RT9535A

Copyright © 2016 Richtek Technology Corporation. All rights reserved.

is a registered trademark of Richtek Technology Corporation.

DS9535A-04

February

2016

www.richtek.com

5

Operation

The RT9535A is a current mode PWM step-down

switching charger controller. The battery DC charge

current is programmed by a resistor R4 at the ISET pin

and the ratio of sense resistor RS2 over RS1 in the

typical application circuit. Amplifier CA converts the

charge current through RS1 to a much lower sampled

ISET pin. Amplifier EA compares the output of CA with

2.5V reference voltage and drives the PWM loop to

DC components. High DC accuracy is achieved with

to go through R4 and generates a ramp signal that is

fed to the PWM control comparator, forming the current

mode inner loop. An internal LDO generates a 5V to

power high-side MOSFET gate driver. For batteries like

lithium that require both constant current and constant

voltage charging, the 0.5% 2.5V reference and the

voltage amplifier VA reduce the charge current when

battery voltage reaches the normal charge voltage level.

For NiMH and NiCd, VA can be used for over-voltage

protection.