RT9736A Datasheet, PDF (14/16 Pages) Richtek Technology Corporation – Dual Channel, Low Resistance Load Switch

RT9736A
Application Information
The RT9736A is a small, low R_ON, dual channel load switch
with EN controlled pins, and is equipped with a charge
pump circuitry to drive the internal N-MOSFET switch.
The product contains two N-MOSFETs that can operate
between input voltage range of 0.8V to 5.5V. It also
supports a maximum current of 6A each channel (T_A =
25°C, 15% Duty Cycle Per Channel, pulse < 300μs). Each
switch is independently controlled by EN pins (EN1 and
EN2), which can directly interface with low-voltage control
signals.
Input and Output
VINx (input) is the power source connection to the internal
circuitry and the Drain of the MOSFET. VOUTx (output) is
the Source of the MOSFET. In a typical application, current
flows through the switch from VINx to VOUTx toward the
load. If VOUTx is greater than VINx, current will flow from
VOUTx to VINx since the MOSFET is bidirectional when
on.
Chip Enable Input
The switch will be disabled when the ENx pin is in a logic
low condition. During this condition, the internal circuitry
and MOSFET will be turned off, reducing the supply current
to 0.1μA typical. Floating the ENx may cause
unpredictable operation. ENx should not be allowed to go
negative with respect to GND.
Supply Filter/Bypass Capacitor
A 1μF or greater low-ESR ceramic capacitor from VIN to
GND, located at the device is strongly recommended to
prevent the input voltage drooping during high current
application. However, higher capacitor values will further
reduce the voltage droop on the input. Furthermore, without
the bypass capacitor, an output short may cause sufficient
ringing on the input (from source lead inductance) to
destroy the internal control circuitry. The input transient
must not exceed 6V of the absolute maximum supply
voltage even for a short duration.
Output Filter Capacitor
A 10 to 1 ratio of supply capacitor to output capacitor from
VOUTx to GND is recommended to prevent the in-rush
currents during low supply voltage start-up. Because the
integrated body diode in the load switch, higher output
capacitor can cause output voltage to exceed supply
voltage when the system supply is removed. A output
capacitor smaller then supply capacitor is recommended
to prevent the current flow through the integrated body
diode from output to system supply.
Charge Pump
The switch has an internal charge pump circuit that is
supplied from VDD pin to afford sufficient bias voltage to
both N-Channel MOSFETs. The recommended VDD voltage
range is 2.5V to 5.5V, and must above VIN for optimal low
R_ON performance, or the value of R_ON will be greater than
the value listed in the ELECTRICAL CHARACTERISTICS
table.
On-Resistance vs. Input Voltage
(VIN > VDD, Single Channel)
100
TA = 25°C, IOUT = −200mA
90
80
VDD = 2.5V
VDD = 3.3V
70
VDD = 3.6V
VDD = 4.2V
60
VDD = 5V
VDD = 5.5V
50
40
30
0.8 1.2 1.6 2 2.4 2.8 3.2 3.6 4 4.4 4.8 5.2 5.6
Input Voltage (V)
Adjustable Rise Time
The RT9736A provides an external adjustable rise time
function. The adjustable rise time is used to prevent large
inrush current and output voltage overshoot while the switch
is being powered-up. The external capacitor connected
from SS pins to GND is charged by a 1μA current source
to set each rise time.
Copyright ©2014 Richtek Technology Corporation. All rights reserved.
www.richtek.com
14
is a registered trademark of Richtek Technology Corporation.
DS9736A-01 June 2014