DS9535A Datasheet, PDF (5/18 Pages) Richtek Technology Corporation – High Efficiency Switching Mode Battery Charge

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
current ICHG (ICHG = IBATT x RS1 / RS2) fed into the
ISET pin. Amplifier EA compares the output of CA with
2.5V reference voltage and drives the PWM loop to
force them to be equal. Note that ICHG has both AC and
DC components. High DC accuracy is achieved with
averaging filter R3 and C3 at ISET pin. ICHG is mirrored
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.
RT9535A
Copyright © 2016 Richtek Technology Corporation. All rights reserved.
DS9535A-04 February 2016
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
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