RT9554A

2

DS9554A-00

June 2014

www.richtek.com

©

Copyright

2014 Richtek Technology Corporation. All rights reserved.

is a registered trademark of Richtek Technology Corporation.

Functional Pin Description

Function Block Diagram

Operation

The RT9554A consists of one current sensing amplifier

and one comparator, and it provides the following

functions : over-current protection and voltage comparison

between AC_REAL and AC_REF. Users can connect one

resistor between the FLAG pin and supply voltage. Either

over-current condition or the occurs AC_REAL voltage is

larger than AC_REF, the FLAG pin is pulled low.

Over Current Protection

With 1m

Ω order of resistor shunts between CSP and CSN,

the current sensing amplifier amplifies the voltage between

CSP and CSN by 200 and compares the result with the

BAT_REF voltage. If the output voltage of current sensing

amplifier is larger than the BAT_REF voltage, the FLAG

pin is pulled low.

AC_REAL & AC_REF Comparison

A comparator is designed for the voltage comparison

between AC_REAL and AC_REF. If the voltage of

AC_REAL is larger than AC_REF, the FLAG pin is pulled

low.

POR

GND

Comparator

+

-

+

-

Comparator

+

-

VRON

AC_REAL

BAT_REF

CSN

CSP

VCC

EN

x 200

FLAG

AC_REF

Pin No.

Pin Name

Pin Function

1

VCC

Power Supply Input. Connect this pin to 5V and place a minimum 0.1

F

decoupling capacitor .The decoupling capacitor should be placed to this pin

as close as possible.

2

EN

Enable Control Input.

3

FLAG

Open-Drain Output. Connected to an external resistor. When over-current

occurs, this pin will be pulled low.

4

AC_REF

Comparator Inverting Input.

5

AC_REAL

Comparator Non-Inverting Input.

6

BAT_REF

Over-Current Threshold Setting. It is used to set over-current threshold from

0.4V to 2V.

7

CSN

Negative Current Sense Input.

8

CSP

Positive Current Sense Input.

9 (Exposed Pad)

GND

Ground. The exposed pad must be soldered to a large PCB and connected to

GND for maximum power dissipation