RT8243A/B/C
5
DS8243A/B/C-07 November 2014 www.richtek.com
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Pin No. Pin Name Pin Function
1 FB1
SMPS1 Feedback Input. Connect FB1 to a resistive voltage divider from SMPS1
output to GND for adjustable output from 2V to 5.5V.
2 ENTRIP1
Channel 1 Enable and Current Limit Setting Input. Connect resistor to GND to set
the threshold for Channel 1 synchronous R
DS(ON)
sense. The GND-PHASE1
current limit threshold is 1/10th the voltage seen at ENTRIP1 over a 0.5V to 3V
range. There is an internal 10A current source from LDO5 to ENTRIP1. Leave
ENTRIP1 floating or drive it above 4.5V to shut down channel 1.
3 TON ON-Time/Frequency Adjustment Input. Connect to GND with 56k to 100k.
4 ENTRIP2
Channel 2 Enable and Current Limit Setting Input. Connect resistor to GND to set
the threshold for Channel 2 synchronous R
DS(ON)
sense. The GND-PHASE2
current limit threshold is 1/10th the voltage seen at ENTRIP2 over a 0.5V to 3V
range. There is an internal 10A current source from LDO5 to ENTRIP2. Leave
ENTRIP2 floating or drive it above 4.5V to shut down channel 2.
5 FB2
SMPS2 Feedback Input. Connect FB2 to a resistive voltage divider from SMPS2
output to GND for adjustable output from 2V to 5.5V.
6 PGOOD
Power Good Output for Channel 1 and Channel 2 (RT8243A).
Power Good Output for Channel 1, Channel 2 and SECFB (RT8243B/C).
7 BOOT2
Boost Flying Capacitor Connection for SMPS2. Connect to an external capacitor
according to the typical application circuits.
8 UGATE2
Upper Gate Driver Output for SMPS2. UGATE2 swings between PHASE2 and
BOOT2.
9 PHASE2
Switch Node for SMPS2. PHASE2 is the internal lower supply rail for the UGATE2
high side gate driver. PHASE2 is also the current sense input for the SMPS2.
10 LGATE2 Lower Gate Drive Output for SMSP2. LGATE2 swings between GND and LDO5.
11 VIN Supply Input for LDO5.
12 ENLDO
Master Enable Input. LDO5/LDO3 is enabled if it is within logic high level and
disabled if it is less than the logic low level. Leave ENLDO floating to default
enable LDO5/LDO3.
13
ENM
(RT8243A)
Mode Selection with Enable Input. Pull up to LDO5 (Ultrasonic mode) or LDO3
(DEM) to turn on both switch Channels. Short to GND for shutdown.
SECFB
(RT8243B/C)
Change Pump Feedback Pin. The SECFB is used to monitor the optional external
charge pump. Connect a resistive divider from the change pump output to GND to
detect the output. If SECFB drops below its feedback threshold, an ultrasonic
pulse occurs to refresh the charge pump driven by LGATE1 or LGATE2.
If SECFB drops below its UV threshold, the switcher channels stop working and
enter into discharge-mode. Pull up to LDO5 or LDO3 to disable SECFB UVP
function.
14 LDO5
5V Linear Regulator Output. LDO5 is the supply voltage for the low side MOSFET
driver and also the analog supply voltage for the device. Bypass a minimum 4.7F
ceramic capacitor to GND
15 LDO3
3.3V Linear Regulator Output. Bypass a minimum 4.7F ceramic capacitor to
GND.
Functional Pin Description
