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RT9745A
Dual Channel, Low Resistance Load Switch
General Description
Features
The RT9745A is a small, low RON, dual channel load switch
with EN controlled pin. The product contains two NMOSFETs that can operate between an input voltage range
of 0.8V to 5.5V. Also, it supports a maximum continuous
current of 6A each channel. Each switch is independently
controlled by EN pins (EN1 and EN2), which can directly
interface with low-voltage control signals.

Integrated Dual Channel Load Switch

Input Voltage Range : 0.8V to 5.5V
Low RON Resistance
 RON = 27mΩ
Ω at VIN = 5V (VDD = 5V)
 RON = 27mΩ
Ω at VIN = 3.6V (VDD = 5V)
 RON = 27mΩ
Ω at VIN = 1.8V (VDD = 5V)
6A Maximum Continuous Switch Current Per
Channel
Low Quiescent Current
 75μ
μA (Both Channels)
 55μ
μA (Single Channel)
Low Control Input Threshold Enables Use of 1.4V/
1.8V/2.5V/3.3V Logics
Configurable Rise Time
Quick Output Discharge (QOD)
Adaptive Discharge Current
14T-Lead WDFN Package with Thermal Pad


The RT9745A is available in the WDFN-14TL 3x2 package
with exposed pad for high power and heat dissipation.

Ordering Information

RT9745A
Package Type
QW : WDFN-14TL 3x2 (W-Type)
Note :

Lead Plating System
G : Green (Halogen Free and Pb Free)



Richtek products are :

RoHS compliant and compatible with the current require-
Applications
ments of IPC/JEDEC J-STD-020.


Suitable for use in SnPb or Pb-free soldering processes.


Marking Information

0P : Product Code

W : Date Code

0PW

UltrabookTM
Notebooks/Netbooks
Tablet PC
Consumer Electronics
Set-Top Boxes/Residential Gateways
Telecom Systems
Solid State Drives (SSD)
Simplified Application Circuit
VIN1
CIN1
Enable
Dual Power
Supply
or
Dual DC/DC
Converter
EN1
Enable
EN2
RL1
SS1
CSS1
SS2
CSS2
VIN2
VOUT2
GND
Copyright © 2014 Richtek Technology Corporation. All rights reserved.
VOUT1
COUT1
VDD
CIN2
DS9745A-00 August 2014
VOUT1
RT9745A
VOUT2
COUT2
RL2
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
1
RT9745A
Pin Configurations
(TOP VIEW)
VIN1
VIN1
EN1
VDD
EN2
VIN2
VIN2
1
14
2
13
3
4
12
GND
5
6
7
11
10
15
9
8
VOUT1
VOUT1
SS1
GND
SS2
VOUT2
VOUT2
WDFN-14TL 3x2
Functional Pin Description
Pin No.
Pin Name
Pin Function
1, 2
VIN1
Input Voltage for Switch 1. Bypass this input with a ceramic capacitor to
GND. Recommended voltage range for this pin for optimal RON performance
is 0.8V to VDD.
3
EN1
Enable Control Input for Switch 1 (Active High). Do not leave floating.
4
VDD
Charge Pump Voltage Input. Power supply to the device. Recommended
voltage range for this pin is 2.5V to 5.5V.
5
EN2
Enable Control Input for Switch 2 (Active High). Do not leave floating.
6, 7
VIN2
Input Voltage for Switch 2. Bypass this input with a ceramic capacitor to
GND. Recommended voltage range for this pin for optimal RON performance
is 0.8V to VDD.
8, 9
VOUT2
Switch 2 Output.
10
SS2
Switch 2 Slew Rate Control. Can be left floating.
11,
15 (Exposed Pad)
GND
Ground. The Exposed pad should be soldered to a large PCB and connected
to GND for maximum thermal dissipation.
12
SS1
Switch 1 Slew Rate Control. Can be left floating.
VOUT1
Switch 1 Output.
13, 14
Copyright © 2014 Richtek Technology Corporation. All rights reserved.
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is a registered trademark of Richtek Technology Corporation.
DS9745A-00 August 2014
RT9745A
Function Block Diagram
VIN1
SS1
EN1
Control Logic
VOUT1
VDD
Charge Pump
GND
VOUT2
EN2
Control Logic
SS2
VIN2
Operation
The RT9745A contains two N-MOSFETs which controlled
by EN pin independently.
Charge Pump
Enable Control
Adjustable Rise Time
Asserting ENx pin high enables the switch. Switch will
turn on as the EN signal is higher than VENH, and turn off
when the EN signal is lower than VENL. Thus, it can operate
under low voltage logic, please refer to the electrical
characteristics. This pin cannot be left floating and must
be tied either high or low voltage for proper functionality.
Connecting a capacitor to GND on the SSx pin sets the
slew rate for each channel. It could also be used to prevent
in-rush current.
Copyright © 2014 Richtek Technology Corporation. All rights reserved.
DS9745A-00 August 2014
Provides sufficient bias voltage to both N-MOSFETs.
is a registered trademark of Richtek Technology Corporation.
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3
RT9745A
Absolute Maximum Ratings









(Note 1)
VIN1, VIN2, EN1, EN2, VDD, VOUT1, VOUT2, SS1, SS2 ------------------------------------------------------Maximum Continuous Switch Current Per Channel, IMAX ------------------------------------------------------Maximum Pulsed Switch Current, Pulse <300μs, 2% Duty Cycle Per Channel, IPLS -------------------Power Dissipation, PD @ TA = 25°C
WDFN-14TL 3x2 -----------------------------------------------------------------------------------------------------------Package Thermal Resistance (Note 2)
WDFN-14TL 3x2, θJA ------------------------------------------------------------------------------------------------------WDFN-14TL 3x2, θJC -----------------------------------------------------------------------------------------------------Junction Temperature -----------------------------------------------------------------------------------------------------Lead Temperature (Soldering, 10 sec.) -------------------------------------------------------------------------------Storage Temperature Range --------------------------------------------------------------------------------------------ESD Susceptibility (Note 3)
HBM (Human Body Model) ----------------------------------------------------------------------------------------------CDM (Charged-Device Model) -------------------------------------------------------------------------------------------
Recommended Operating Conditions





−0.3V to 6V
6A
8A
3.11W
32.1°C/W
6.3°C/W
150°C
260°C
−65°C to 150°C
2kV
1kV
(Note 4)
VIN1,2, Input Voltage Range ---------------------------------------------------------------------------------------------VDD, Charge Pump Input Voltage Range -----------------------------------------------------------------------------VEN1,2, EN Voltage Range -----------------------------------------------------------------------------------------------Junction Temperature Range --------------------------------------------------------------------------------------------Ambient Temperature Range ---------------------------------------------------------------------------------------------
0.8V to VDD
2.5V to 5.5V
0V to VDD
−40°C to 125°C
−40°C to 85°C
Electrical Characteristics
(VIN = 0.8V to 5.5V, TA = 25°C, unless otherwise specified)
Parameter
Symbol
Test Conditions
Min
Typ
Max
Unit
EN Input Supply
Input Voltage
High-Level
VENH
1.4
--
5.5
Low-Level
VENL
0
--
0.5
--
--
1
A
Min
Typ
Max
Unit
--
75
115
A
ENx Pin Input Leakage Current IEN
VEN = 5.5V
V
(VDD = 5V, VIN = 0.8V to VDD, TA = 25°C, unless otherwise specified)
Parameter
Symbol
Test Conditions
Power Supplies and Currents
VDD Quiescent Current
(Both Channels)
IIN(VDD, ON)
IOUT1 = IOUT2 = 0A
VIN1,2 = VEN1,2 = VDD = 5V
IOUT1 = IOUT2 = 0A
VDD Quiescent Current
(Single Channel)
IIN(VDD, ON)
VIN1,2 = VEN1 = VDD = 5V,
VEN2 = GND
--
55
--
A
VDD Shutdown Current
IIN(VDD, OFF)
VEN1,2 = GND, VOUT1,2 = 0V
--
--
2
A
Copyright © 2014 Richtek Technology Corporation. All rights reserved.
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is a registered trademark of Richtek Technology Corporation.
DS9745A-00 August 2014
RT9745A
Parameter
Symbol
VIN1,2 Off-State Supply Current
IIN(VIN, OFF)
(Per Channel)
Test Conditions
Min
Typ
Max
VIN1,2 = 5V
--
--
8
VIN1,2 = 3.3V
--
--
3
VIN1,2 = 1.8V
--
--
2
VIN1,2 = 0.8V
--
--
1
VIN = 5V
--
27
30
VIN = 3.3V
--
27
30
VIN = 1.8V
--
27
30
VIN = 1.5V
--
27
30
VIN = 1.2V
--
27
30
VIN = 0.8V
--
27
30
VEN = 0V, VIN = 5V, IOUT = 15mA
--
220
300
VEN1,2 = GND,
VOUT1,2 = 0V
Unit
A
Resistance Characteristics
ON-State Resistance
Output Pull-down Resistance
RON
RPD
IOUT = 200mA,
VDD = 5V
m

Note 1. Stresses beyond those listed “Absolute Maximum Ratings” may cause permanent damage to the device. These are
stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in
the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions may
affect device reliability.
Note 2. θJA is measured at TA = 25°C on a high effective thermal conductivity four-layer test board per JEDEC 51-7. θJC is
measured at the exposed pad of the package.
Note 3. Devices are ESD sensitive. Handling precaution is recommended.
Note 4. The device is not guaranteed to function outside its operating conditions.
Copyright © 2014 Richtek Technology Corporation. All rights reserved.
DS9745A-00 August 2014
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
5
RT9745A
Typical Application Circuit
VIN1
0.8V to 5.5V
1, 2
CIN1
CIN2
VIN1
3 EN1
VDD
2.5V to 5.5V
4 VDD
Enable
5 EN2
6, 7
CIN3
13, 14
RT9745A
Enable
VIN2
0.8V to 5.5V
VOUT1
COUT1
SS1
CSS1
SS2
10
CSS2
VOUT2
11, 15 (Exposed Pad)
RL1
12
VIN2
CIN4
VOUT1
8, 9
VOUT2
COUT2
GND
RL2
Timing Diagram
VIN
+
-
CIN
Enable
VOUT
RT9745A
EN
VDD
VOUT
COUT
RL
GND
Single Channel Shown for Clarity
TEST CIRCUIT
VEN
50%
50%
VOUT
50%
tf
tr
tOFF
tON
50%
90%
VOUT
10%
90%
10%
tD
Figure 1. Test Circuit and tON/tOFF Waveforms
Copyright © 2014 Richtek Technology Corporation. All rights reserved.
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is a registered trademark of Richtek Technology Corporation.
DS9745A-00 August 2014
RT9745A
Timing Characteristics
Parameter
Test Conditions
Min
Typ
Max
Unit
VIN = EN = VDD = 5V, TA = 25C
TON
Turn-On Time
RL = 10, COUT = 0.1F, CSS = 1000pF
--
1220
--
TOFF
Turn-Off Time
RL = 10, COUT = 0.1F, CSS = 1000pF
--
4
--
TR
VOUT Rise Time
RL = 10, COUT = 0.1F, CSS = 1000pF
--
1350
--
TF
VOUT Fall Time
RL = 10, COUT = 0.1F, CSS = 1000pF
--
3
--
TD
ON Delay Time
RL = 10, COUT = 0.1F, CSS = 1000pF
--
400
--
s
VIN = 0.8V, EN = VDD = 5V, TA = 25C
TON
Turn-On Time
RL = 10, COUT = 0.1F, CSS = 1000pF
--
580
--
TOFF
Turn-Off Time
RL = 10, COUT = 0.1F, CSS = 1000pF
--
80
--
TR
VOUT Rise Time
RL = 10, COUT = 0.1F, CSS = 1000pF
--
280
--
TF
VOUT Fall Time
RL = 10, COUT = 0.1F, CSS = 1000pF
--
20
--
TD
ON Delay Time
RL = 10, COUT = 0.1F, CSS = 1000pF
--
400
--
s
VIN = EN = VDD = 3.3V, TA = 25C
TON
Turn-On Time
RL = 10, COUT = 0.1F, CSS = 1000pF
--
960
--
TOFF
Turn-Off Time
RL = 10, COUT = 0.1F, CSS = 1000pF
--
6
--
TR
VOUT Rise Time
RL = 10, COUT = 0.1F, CSS = 1000pF
--
940
--
TF
VOUT Fall Time
RL = 10, COUT = 0.1F, CSS = 1000pF
--
3
--
TD
ON Delay Time
RL = 10, COUT = 0.1F, CSS = 1000pF
--
400
--
s
VIN = 0.8V, EN = VDD = 3.3V, TA = 25C
TON
Turn-On Time
RL = 10, COUT = 0.1F, CSS = 1000pF
--
560
--
TOFF
Turn-Off Time
RL = 10, COUT = 0.1F, CSS = 1000pF
--
175
--
TR
VOUT Rise Time
RL = 10, COUT = 0.1F, CSS = 1000pF
--
280
--
TF
VOUT Fall Time
RL = 10, COUT = 0.1F, CSS = 1000pF
--
40
--
TD
ON Delay Time
RL = 10, COUT = 0.1F, CSS = 1000pF
--
400
--
Copyright © 2014 Richtek Technology Corporation. All rights reserved.
DS9745A-00 August 2014
s
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
7
RT9745A
Typical Operating Characteristics
Quiescent Current vs. VDD
Quiescent Current vs. VDD
50
Both Channels
Quiescent Current (μA) 1
Quiescent Current (μA)
50
40
85°C
25°C
−40°C
30
20
3.1
3.4
3.7
4
4.3
85°C
25°C
−40°C
30
20
10
10
2.8
40
VIN1 = VIN2 = VDD, VEN1 = 0V, VEN2 = 5V,
VOUT = Open, VUT1 = Off, VUT2 = On
VIN1 = VIN2 = VDD, VEN1 = VEN2 = 5V,
VOUT = Open, VUT1 = On, VUT2 = On
2.5
Single Channel
4.6
4.9
5.2
2.5
5.5
2.8
3.1
3.4
3.7
Off-State Supply Current (μA)
Shut-Down Current (μA)1
0.08
0.06
85°C
0.04
−40°C
0.02
25°C
0.00
3.4
3.7
4
4.3
4.6
4.9
5.2
0.4
0.2
85°C
25°C
−40°C
0.1
0.0
-0.1
-0.2
-0.3
-0.4
-0.5
VDD = 5.5V, VEN = 0V, VOUT = 0V
0.8 1.2 1.6
5.5
2
2.4 2.8 3.2 3.6
35
2.5V
1.8V
1.5V
1.2V
1.05V
0.8V
Single Channel
40
30
25
20
15
4.4 4.8 5.2 5.6
On-Resistance vs. Temperature
45
On-Resistance (mΩ)
On-Resistance (mΩ)
40
4
Input Voltage (V)
Single Channel
=
=
=
=
=
=
5.5
0.3
On-Resistance vs. Temperature
VIN
VIN
VIN
VIN
VIN
VIN
5.2
Single Channel
VDD (V)
45
4.9
0.5
Both Channels
VIN1 = VIN2 = VDD, VEN1 = VEN2 = 0V, VOUT = 0V
3.1
4.6
Off-State Supply Current vs. Input Voltage
Shut-Down Current vs. VDD
0.10
2.8
4.3
VDD (V)
VDD (V)
2.5
4
VIN
VIN
VIN
VIN
VIN
VIN
35
30
=
=
=
=
=
=
0.8V
1.05V
1.2V
1.5V
1.8V
2.5V
VIN
VIN
VIN
VIN
VIN
=
=
=
=
=
3.3V
3.6V
4.2V
5V
5.5V
25
20
VDD = 2.5V, IOUT = −200mA
-40
-15
10
15
35
60
Temperature (°C)
Copyright © 2014 Richtek Technology Corporation. All rights reserved.
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8
85
VDD = 5.5V, IOUT = −200mA
-40
-15
10
35
60
85
Temperature (°C)
is a registered trademark of Richtek Technology Corporation.
DS9745A-00 August 2014
RT9745A
On-Resistance vs. Input Voltage
45
On-Resistance vs. Input Voltage
45
Single Channel
40
On-Resistance (mΩ)
On-Resistance (mΩ)
40
Single Channel
35
85°C
30
25°C
25
−40°C
20
0.8
1.14
1.48
85°C
30
25°C
25
−40°C
20
VDD = 2.5V, IOUT = −200mA
15
35
1.82
2.16
VDD = 5.5V, IOUT = −200mA
15
2.5
0.8 1.2 1.6
2
Input Voltage (V)
VDD
VDD
VDD
VDD
VDD
VDD
32
30
=
=
=
=
=
=
360
2.5V
3.3V
3.6V
4.2V
5V
5.5V
Discharge Resistance (Ω)
On-Resistance (mΩ)
Single Channel
34
28
26
24
22
2
2.4 2.8 3.2 3.6
4
Single Channel
320
280
240
85°C
25°C
−40°C
200
160
120
80
40
TA = 25°C, IOUT = −200mA
0.8 1.2 1.6
VDD = 5.5V, VEN = 0V
0
0.8 1.2 1.6
4.4 4.8 5.2 5.6
2
4
4.4 4.8 5.2 5.6
On Delay Time vs. Input Voltage
Output Voltage vs. Enable Voltage
600
Single Channel
550
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
VDD
VDD
VDD
VDD
VDD
VDD
=
=
=
=
=
=
2.5V
3.3V
3.6V
4.2V
5V
5.5V
On Delay Time (ms)
Output Voltage (V)
2.4 2.8 3.2 3.6
Input Voltage (V)
Input Voltage (V)
2.6
2.4
2.2
4.4 4.8 5.2 5.6
Discharge Resistance vs. Input Voltage
400
20
4
Input Voltage (V)
On-Resistance vs. Input Voltage
36
2.4 2.8 3.2 3.6
500
−40°C
450
25°C
400
350
300
85°C
250
VIN = 2.5V, TA = 25°C
0
0.5
1
1.5
2
Enable Voltage (V)
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DS9745A-00 August 2014
2.5
VDD = 2.5V, CSS = 1nF
200
0.8
1
1.2
1.4
1.6
1.8
2
2.2
2.4
2.6
Input Voltage (V)
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RT9745A
On Delay Time vs. Input Voltage
VDD = 5.5V, CSS = 1nF
550
On Delay Time (ms)
On Delay Time vs. VDD
600
−40°C
500
On Delay Time (μs)
600
450
25°C
400
350
85°C
300
VIN1 = VIN2 = 2.5V, CSS = 1nF
500
−40°C
25°C
400
85°C
300
250
200
200
0.8 1.2 1.6
2
2.4 2.8 3.2 3.6
4
4.4 4.8 5.2 5.6
2.5
2.8
3.1
3.4
Input Voltage (V)
VDD = 2.5V, CSS = 1nF
4.6
4.9
5.2
5.5
VDD = 5.5V, CSS = 1nF
35
60
Off Fall Time (μs)
Off Fall Time (μs)
4.3
Off Fall Time vs. Input Voltage
40
70
−40°C
25°C
85°C
50
40
30
20
10
30
25
85°C
25°C
−40°C
20
15
10
5
0
0
0.8
1
1.2
1.4
1.6
1.8
2
2.2
2.4
2.6
0.8 1.2 1.6
2
Input Voltage (V)
2.4 2.8 3.2 3.6
4
4.4 4.8 5.2 5.6
Input Voltage (V)
Off Fall Time vs. VDD
Off Time vs. Input Voltage
5
300
VIN = 2.5V, CSS = 1nF
VDD = 2.5V, CSS = 1nF
250
4
85°C
3
25°C
2
−40°C
Off Time (μs)
Off Fall Time (μs)
4
VDD (V)
Off Fall Time vs. Input Voltage
80
3.7
1
−40°C
25°C
85°C
200
150
100
50
0
0
2.5
2.8
3.1
3.4
3.7
4
4.3
4.6
4.9
5.2
VDD (V)
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5.5
0.8
1
1.2
1.4
1.6
1.8
2
2.2
2.4
2.6
Input Voltage (V)
is a registered trademark of Richtek Technology Corporation.
DS9745A-00 August 2014
RT9745A
Off Time vs. Input Voltage
Off Time vs. VDD
20
150
15
85°C
25°C
−40°C
90
Off Time (μs)
Off Time (μs)
120
60
85°C
10
25°C
5
30
−40°C
VDD = 5.5V, CSS = 1nF
VIN = 2.5V, CSS = 1nF
0
0
0.8 1.2 1.6
2
2.4 2.8 3.2 3.6
4
2.5
4.4 4.8 5.2 5.6
2.8
3.1
3.4
Input Voltage (V)
On Time vs. Input Voltage
4.3
4.6
4.9
5.2
5.5
On Time vs. Input Voltage
1600
900
800
700
25°C
600
85°C
500
0.8
1
1.2
1.4
1.6
1200
1000
800
600
VDD = 2.5V, CSS = 1nF
400
−40°C
25°C
85°C
1400
−40°C
On Time (ms)
On Time (ms)
4
VDD (V)
1000
1.8
2
2.2
2.4
VDD = 5.5V, CSS = 1nF
400
2.6
0.8 1.2 1.6
2
Input Voltage (V)
On Rising Time (μs)
25°C
700
VIN = 2.5V, CSS = 1nF
2.5
2.8
3.1
3.4
3.7
4
4.3
4.6
4.9
5.2
VDD (V)
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DS9745A-00 August 2014
−40°C
25°C
85°C
800
600
400
200
85°C
600
4.4 4.8 5.2 5.6
1000
−40°C
800
4
On Rising Time vs. Input Voltage
On Time vs. VDD
900
2.4 2.8 3.2 3.6
Input Voltage (V)
1000
On Time (ms)
3.7
5.5
VDD = 2.5V, CSS = 1nF
0
0.8
1
1.2
1.4
1.6
1.8
2
2.2
2.4
2.6
Input Voltage (V)
is a registered trademark of Richtek Technology Corporation.
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RT9745A
On Rising Time vs. Input Voltage
On Rising Time vs. VDD
2000
1000
1600
−40°C
25°C
85°C
1400
1200
On Rising Time (μs)
On Rising Time (μs)
1800
1000
800
600
400
200
VDD = 5.5V, CSS = 1nF
0
0.8 1.2 1.6
2
2.4 2.8 3.2 3.6
4
4.4 4.8 5.2 5.6
900
−40°C
800
25°C
700
85°C
600
VIN = 2.5V, CSS = 1nF
500
2.5
3.7
4
4.3
4.6
4.9
Turn-On Response Time
EN1
(5V/Div)
VOUT2
(500mV/Div)
EN1
(5V/Div)
VOUT2
(500mV/Div)
VIN = 0.8V, VDD = 2.5V,
CIN = 1μF, COUT = 0.1μF, RL = 10Ω
EN2
(5V/Div)
Time (500μs/Div)
Turn-On Response Time
Turn-On Response Time
VOUT1
(5V/Div)
EN1
(5V/Div)
VOUT2
(2V/Div)
EN1
(5V/Div)
VOUT2
(5V/Div)
VIN = 2.5V, VDD = 2.5V,
CIN = 1μF, COUT = 0.1μF, RL = 10Ω
Time (500μs/Div)
Copyright © 2014 Richtek Technology Corporation. All rights reserved.
EN2
(5V/Div)
5.2
5.5
VIN = 0.8V, VDD = 5V,
CIN = 1μF, COUT = 0.1μF, RL = 10Ω
Time (500μs/Div)
VOUT1
(2V/Div)
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12
3.4
Turn-On Response Time
VOUT1
(500mV/Div)
EN2
(5V/Div)
3.1
VDD (V)
VOUT1
(500mV/Div)
EN2
(5V/Div)
2.8
Input Voltage (V)
VIN = 5V, VDD = 5V,
CIN = 1μF, COUT = 0.1μF, RL = 10Ω
Time (500μs/Div)
is a registered trademark of Richtek Technology Corporation.
DS9745A-00 August 2014
RT9745A
Turn-Off Response Time
Turn-Off Response Time
VOUT1
(500mV/Div)
EN1
(5V/Div)
VOUT1
(500mV/Div)
EN1
(5V/Div)
VOUT2
(500mV/Div)
EN2
(5V/Div)
VOUT2
(500mV/Div)
EN2
(5V/Div)
VIN = 0.8V, VDD = 5V,
CIN = 1μF, COUT = 0.1μF, RL = 10Ω
VIN = 0.8V, VDD = 2.5V,
CIN = 1μF, COUT = 0.1μF, RL = 10Ω
Time (50μs/Div)
Time (50μs/Div)
Turn-Off Response Time
Turn-Off Response Time
VOUT1
(2V/Div)
EN1
(5V/Div)
VOUT1
(5V/Div)
EN1
(5V/Div)
VOUT2
(2V/Div)
EN2
(5V/Div)
VOUT2
(5V/Div)
EN2
(5V/Div)
VIN = 2.5V, VDD = 2.5V,
CIN = 1μF, COUT = 0.1μF, RL = 10Ω
Time (50μs/Div)
Copyright © 2014 Richtek Technology Corporation. All rights reserved.
DS9745A-00 August 2014
VIN = 5V, VDD = 5V,
CIN = 1μF, COUT = 0.1μF, RL = 10Ω
Time (50μs/Div)
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
13
RT9745A
Application Information
The RT9745A is a small, low RON, 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-channel MOSFETs that can
operate between input voltage range of 0.8V to 5.5V. It
also supports a maximum continuous current of 6A each
channel and a maximum pulsed switch current of 8A (pulse
<300μs). Each switch is independently controlled by EN
pins (EN1 and EN2), which can directly interface with lowvoltage control signals.
Output Filter Capacitor
Input and Output
Charge Pump
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.
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
RON performance, or the value of RON will be greater than
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.
the value listed in the ELECTRICAL CHARACTERISTICS
table.
On-Resistance
Input Voltage
Voltage
On-Resistance vs.
vs. Input
(VIN
Single Channel)
Channel)
(VIN >> VDD, Single
Chip Enable Input
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.
Copyright © 2014 Richtek Technology Corporation. All rights reserved.
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14
100
90
On-Resistance (mΩ)
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.
TA = 25°C, IOUT = −200mA
80
70
60
50
VDD
VDD
VDD
VDD
VDD
VDD
=
=
=
=
=
=
2.5V
3.3V
3.6V
4.2V
5V
5.5V
40
30
20
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 RT9745A 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.
is a registered trademark of Richtek Technology Corporation.
DS9745A-00 August 2014
RT9745A
Discharge Operation
Thermal Considerations
For continuous operation, do not exceed absolute
maximum junction temperature. The maximum power
dissipation depends on the thermal resistance of the IC
package, PCB layout, rate of surrounding airflow, and
difference between junction and ambient temperature. The
maximum power dissipation can be calculated by the
following formula :
Maximum Power Dissipation (W)1
When ENx is low, the RT9745A will discharge the system
residual voltage using internal MOSFET connected
between the VOUTx and GND. The discharge current
depends on the voltage at the VOUTx pin. When the
voltage at the VOUTx is lower than 0.8V, the RT9745A
will fully turn the internal MOSFET on to pull the VOUTx
low.
3.5
Four-Layer PCB
3.0
2.5
2.0
1.5
1.0
0.5
0.0
0
25
50
75
100
125
Ambient Temperature (°C)
Figure 2. Derating Curve of Maximum Power Dissipation
PD(MAX) = (TJ(MAX) − TA) / θJA
where TJ(MAX) is the maximum junction temperature, TA is
the ambient temperature, and θJA is the junction to ambient
thermal resistance.
For recommended operating condition specifications, the
maximum junction temperature is 125°C. The junction to
ambient thermal resistance, θJA, is layout dependent. For
WDFN-14TL 3x2 package, the thermal resistance, θJA, is
32.1°C/W on a standard JEDEC 51-7 four-layer thermal
test board. The maximum power dissipation at TA = 25°C
can be calculated by the following formula :
PD(MAX) = (125°C − 25°C) / (32.1°C/W) = 3.11W for
WDFN-14TL 3x2 package
The maximum power dissipation depends on the operating
ambient temperature for fixed T J(MAX) and thermal
resistance, θJA. The derating curve in Figure 2 allows the
designer to see the effect of rising ambient temperature
on the maximum power dissipation.
Copyright © 2014 Richtek Technology Corporation. All rights reserved.
DS9745A-00 August 2014
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
15
RT9745A
Outline Dimension
2
1
2
1
DETAIL A
Pin #1 ID and Tie Bar Mark Options
Note : The configuration of the Pin #1 identifier is optional,
but must be located within the zone indicated.
Symbol
Dimensions In Millimeters
Dimensions In Inches
Min.
Max.
Min.
Max.
A
0.700
0.800
0.028
0.031
A1
0.000
0.050
0.000
0.002
A3
0.175
0.250
0.007
0.010
b
0.150
0.250
0.006
0.010
b1
0.550
0.650
0.022
0.026
D
2.900
3.100
0.114
0.122
D2
2.450
2.550
0.096
0.100
E
1.900
2.100
0.075
0.083
E2
0.850
0.950
0.033
0.037
e
0.400
0.016
K
0.200
0.008
K1
0.120
0.005
L
0.300
0.400
0.012
0.016
W-Type 14TL DFN 3x2 Package
Richtek Technology Corporation
14F, No. 8, Tai Yuen 1st Street, Chupei City
Hsinchu, Taiwan, R.O.C.
Tel: (8863)5526789
Richtek products are sold by description only. Richtek reserves the right to change the circuitry and/or specifications without notice at any time. Customers should
obtain the latest relevant information and data sheets before placing orders and should verify that such information is current and complete. Richtek cannot
assume responsibility for use of any circuitry other than circuitry entirely embodied in a Richtek product. Information furnished by Richtek is believed to be
accurate and reliable. However, no responsibility is assumed by Richtek or its subsidiaries for its use; nor for any infringements of patents or other rights of third
parties which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of Richtek or its subsidiaries.
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16
DS9745A-00 August 2014
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