RT9705B
80mΩ, 1A Power Multiplexer
Ω
General Description
The RT9705B is a dual input single output power
multiplexer specifically designed to provide seamless
voltage transition between two independent power
suppliers. Equipped with two low R
DS(ON)
N-Channel
MOSFETs driven by internal charge pump circuitry, the
RT9705B is able to deliver 1A output current with only
80mV voltage drop. Manual or auto switching mode is easily
selected by two digital inputs D1 and D0. When both D0
and D1 are selected high, the RT9705B enters shutdown
mode and consumes minimum power making it ideal
suitable for battery powered equipments. A STAT pin with
open drain output is provided to indicate the switch status.
A user-programmable up to 1.25A current limit function is
available for maximum safety in various applications.
The RT9705B provides comprehensive protection functions,
including adjustable current limit, over temperature
protection, soft start function for minimum inrush current,
cross-conduction protection, and reverse conduction
protection. These features greatly simplify power
multiplexer design. The RT9705B is available in TSSOP-8
package requiring minimum board area and smallest
components.
Features
Adjustable Current Limiting up to 1.25A
Built-In (Typically 80mΩ) N-Channel MOSFET
Ω
Reverse Current Flow Blocking (no body diode) i.e.
Output Can Be Forced Higher than Input (Off-State)
Low Supply Current :
μ
55μA Typical at Switch on State
Less than 0.5μA Typical at Switch Off State
μ
Guaranteed 1A Continuous Load Current
Wide Input Voltage Ranges : 2.8V to 5.5V
Open-Drain STAT Output
Hot Plug-In Application (Soft-Start)
Thermal Shutdown Protection
Smallest TSSOP-8 Package Minimizes Board Space
RoHS Compliant and 100% Lead (Pb)-Free
Applications
LCD Monitor, LCD-TV
Information Appliance and Set-Top Box
Battery-Powered Equipment
ACPI Power Distribution
Motherboard & Notebook PCs
Mini PCI & PCI-Express Cards
PCMCIA & New Cards
Ordering Information
RT9705B
Package Type
C : TSSOP-8
Lead Plating System
P : Pb Free
G : Green (Halogen Free and Pb Free)
Note :
Richtek products are :
RoHS compliant and compatible with the current require-
ments of IPC/JEDEC J-STD-020.
Suitable for use in SnPb or Pb-free soldering processes.
STAT
D0
D1
ILIM
Marking Information
For marking information, contact our sales representative
directly or through a Richtek distributor located in your
area.
Pin Configurations
(TOP VIEW)
8
7
6
5
VIN1
VOUT
VIN2
GND
2
3
4
TSSOP-8
DS9705B-03 April 2011
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1
RT9705B
Typical Application Circuit
V
IN1
Switch Status
0.1uF
R1
V
OUT
C
OUT
R
LOAD
1
D0
D1
R
ILIM
2
STAT
D0
VIN1 8
7
VOUT
RT9705B
3
D1
VIN2 6
ILIM
GND
5
4
V
IN2
0.1uF
Functional Pin Description
Pin Name
VIN1
VIN2
VOUT
GND
STAT
D0, D1
ILIM
Power Input1 Voltage
Power Input2 Voltage
Output Voltage
Ground
STAT is an open-drain output that is Hi-Z if the VIN2 switch is ON.
The truth table shown below illustrates the functionality of D0 and D1.
A resistor R
ILIM
from ILIM to GND sets the current limit I
LIM
to (500/R
ILIM
).
Pin Function
Table 1. Truth Table
D1
0
0
0
1
1
Notes for Table 1.
1. X : Don’ t care
2. Hi-Z: High impedance node
3. D0 and D1 cannot be floating which will lead to an unknown state.
4. An internal MOSFET with 2kΩ R
DS(ON)
turns on and softly discharges the output voltage when D0 = D1 = 1.
D0
0
1
1
0
1
V
IN2
>V
IN1
X
No
Yes
X
X
STAT
Hi-Z
0
Hi-Z
0
0
V
OUT
V
IN2
V
IN1
V
IN2
V
IN1
0
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2
DS9705B-03 April 2011
RT9705B
Absolute Maximum Ratings
(Note 1)
Input Voltage, VIN1 & VIN2 -----------------------------------------------------------------------------------------
−
0.3V to 6.0V
Logic Inputs Voltage, D0 &D1 --------------------------------------------------------------------------------------
−
0.3V to 6.0V
Output Voltage, VOUT, STAT & ILIM -----------------------------------------------------------------------------
−
0.3V to 6.0V
Power Dissipation, P
D
@ T
A
= 25°C
TSSOP-8 ----------------------------------------------------------------------------------------------------------------
0.43W
Package Thermal Resistance (Note 2)
TSSOP-8,
θ
JA
---------------------------------------------------------------------------------------------------------- 230°C/W
Junction Temperature ------------------------------------------------------------------------------------------------- 125°C
Lead Temperature (Soldering, 10 sec.) --------------------------------------------------------------------------- 260°C
Storage Temperature Range ----------------------------------------------------------------------------------------
−
65°C to 150°C
ESD Susceptibility (Note 3)
HBM (Human Body Mode) ------------------------------------------------------------------------------------------ 2kV
MM (Machine Mode) -------------------------------------------------------------------------------------------------- 200V
Recommended Operating Conditions
Input Voltage
(Note 4)
V
IN1
( if V
IN2
≥
2.8V) -------------------------------------------------------------------------------------------------- 2.3V to 5.5V
V
IN1
( if V
IN2
< 2.8V) -------------------------------------------------------------------------------------------------- 2.8V to 5.5V
V
IN2
( if V
IN1
≥
2.8V) -------------------------------------------------------------------------------------------------- 2.3V to 5.5V
V
IN2
( if V
IN1
< 2.8V) -------------------------------------------------------------------------------------------------- 2.8V to 5.5V
Logic Inputs Voltage (D0 &D1) ------------------------------------------------------------------------------------- 0V to 5.5V
Junction Temperature Range ----------------------------------------------------------------------------------------
−
40°C to 125°C
Ambient Temperature Range ----------------------------------------------------------------------------------------
−
40°C to 85°C
Electrical Characteristics
(V
IN1
= V
IN2
=
3.6V, C
IN
=
C
OUT
= 1μF, R
ILIM
= 400
Ω,
T
A
= 25°C, unless otherwise specified)
Parameter
Power Switch
Symbol
Test Conditions
Min
Typ
Max
Unit
V
IN1
= V
IN2
= 3.6V, I
OUT
= 1A
Switch On Resistance
Logic Inputs (D0 and D1)
Logic Low to High Threshold Voltage V
TH_LH
Threshold Hysteresis
Input Current at D0 or D1
V
TH_HYS
I
IL
I
IH
D0 or D1 = High, Sink Current
D0 or D1 = Low, Source Current
R
DS(ON
)
V
IN1
= V
IN2
= 3.6V, I
OUT
= 1A
−5°C ≤
T
A
≤
85°C
(Note 5)
--
--
80
--
95
120
mΩ
1.5
--
--
--
--
500
--
--
2.1
--
1
1
V
mV
μA
To be continued
DS9705B-03 April 2011
www.richtek.com
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