400mA/200mA Dual 3.3V Smart
Power Switch
SC1543
PRELIMINARY - October 9, 2000
TEL:805-498-2111 FAX:805-498-3804 WEB:http://www.semtech.com
DESCRIPTION
The SC1543 provides a glitch free 3.3V output when
one of two 3.3V input sources is present. It does not
require external logic to sequence from one input
source to the other. Whenever VIN1 exceeds a
predetermined threshold value the internal MOSFET
connects it’s source voltage to the output. If the input at
VIN1 is below the threshold another internal MOSFET
connects VIN2 to the output. If both inputs are at 3.3V
then VIN1 will be connected to the output.
The SC1543 is designed to provide 400mA from the
main input (VIN1) and 200mA from the secondary input
(VIN2). A very low quiescent current of 10µA in
shutdown mode reduces power dissipation.
The internal logic and control circuit detects the voltage
levels of VIN1 and VIN2, and compares them to an
input reference voltage of 2.9V. An internally controlled
period of switch overlap ensures that the transition
between supplies is as glitch-free as possible.
The SC1543 is available in an MSOP-8 surface mount
package.
FEATURES
Glitch free transitions between inputs
•=
•= Internal logic selects appropriate input
•= 400mA load current capability from main input
•= Low power shutdown mode
•= Industrial temperature range
APPLICATIONS
•= Mini PCI cards
•= Peripheral cards
•= Instantly available personal computers (IAPCs)
ORDERING INFORMATION
Part Number
SC1543IMSTR MSOP-8
Note:
(1) Only available in tape and reel packaging. A reel
contains 2500 devices.
(1)
Package
APPLICATION CIRCUIT
SHUTDOWN
3.3V IN
3.3VAUX IN
CIN1
1uF
CIN2
1uF
U1
1
VIN1
SHDN
2
VIN1
3
VIN2
4 5
VIN2 GND
VOUT
VOUT
SC1543
8
7
6
COUT
10uF
3.3V OUT
1
© 2000 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320
400mA/200mA Dual 3.3V Smart
SC1543
Power Switch
PRELIMINARY - October 9, 2000
ABSOLUTE MAXIMUM RATINGS
Parameter Symbol Maximum Units
Input Supply Voltage VIN1,2 -0.5 to +6 V
Output Current From:
VIN1
VIN2
I
O
400
200
mA
Operating Ambient Temperature Range T
Operating Junction Temperature Range T
Storage Temperature Range T
Lead Temperature (Soldering, 10 Sec.) T
Thermal Impedance Junction to Ambient
ELECTRICAL CHARACTERISTICS
Unless specified, TA = 25°C, SHDN = 0V, CO = 10µF, IO = 400mA (when power is being supplied from VIN1, 200mA when power is being supplied from VIN2). Val ues in bold apply over full operating temperat ure range.
(1)
STG
LEAD
θ
JA
A
J
-40 to +85 °C
-40 to +125 °C
-65 to +150 °C
300 °C
206 °C/W
Parameter Symbol Conditions Min Typ Max Units
VIN1
Supply Voltage VIN1
Quiescent Current I
Reverse Leakage From VIN2
(2)
I
Q1
VIN1
VIN1 > VIN2, IO = 0mA 150
VIN1 < VIN2 15
VIN1 = SHDN = 3.3V 1
VIN1 = 0V, VIN2 = 3.6V, IO = 0mA 0.25
3.0
3.3
3.6
300
50
10
1.00
V
µA
µA
VIN2
Supply Voltage VIN2
3.0
3.3
3.6
V
Quiescent Current I
Reverse Leakage From VIN1
(2)
I
Q2
VIN2
VIN2 > VIN1, IO = 0mA 150
VIN2 < VIN1 1
VIN2 = SHDN = 3.3V 1
VIN1 = 3.6V, VIN2 = 0V, IO = 0mA 0.25
300
10
10
1.00
µA
µA
VIN1 Threshold Voltage
Threshold Voltage V
Hysteresis V
TH
HYST
2.80
2.90
3.00
V
130 mV
Power Switches
VIN1 Pass Device R
VIN2 Pass Device R
DS(ON)
DS(ON)
(2)
(2)
R
DS(ON)1
R
DS(ON)2
VIN1 = 3.3V, VIN2 = 0V 100
VIN1 = 0V, VIN2 = 3.3V 150
250
400
mΩ
mΩ
2
© 2000 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320
400mA/200mA Dual 3.3V Smart
SC1543
Power Switch
PRELIMINARY - October 9, 2000
ELECTRICAL CHARACTERISTICS
Unless specified, TA = 25°C, SHDN = 0V, CO = 10µF, IO = 400mA (when power is being supplied from VIN1, 200mA when power is being supplied from VIN2). Val ues in bold apply over full operating temperat ure range.
Parameter Symbol Conditions Min Typ Max Units
SHDN
(1)
(Cont.)
Input High Voltage V
Input Low Voltage V
IH
IL
Over Temperature Protection
High Trip Level T
Hysteresis T
HI
HYS
NOTES:
(1) This device is ESD sensitive. Use of standard ESD handling precautions is required.
(2) Guaranteed by design.
OUTPUT TRUTH TABLE
TH
TH
(1)
VOUT
Connected to VIN1
Connected to greater of VIN1 and VIN2
.
TH
Input Conditions
VIN1 > V
VIN1 < V
NOTES:
(1) See Electrical Characteristics for definition for V
1.8
165 °C
20 °C
0.4
V
V
3
© 2000 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320
PRELIMINARY - October 9, 2000
BLOCK DIAGRAM
400mA/200mA Dual 3.3V Smart
Power Switch
SC1543
PIN CONFIGURATION
Top View
(MSOP-8)
PIN DESCRIPTION
Pin Pin Name Pin Function
1,2 VIN1 Primary input supply, nominally 3.3V.
3,4 VIN2 Secondary input supply, nominally 3.3V.
5 GND Power and logic ground.
6,7 VOUT 3.3V out.
8 SHDN Shutdown, with internal pull-down. Device is OFF when this pin is High. Leave open if shut-
down feature is not required.
4
© 2000 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320
PRELIMINARY - October 9, 2000
OUTLINE DRAWING - MSOP-8
400mA/200mA Dual 3.3V Smart
Power Switch
SC1543
LAND PATTERN - MSOP-8
ECN00-1361
5
© 2000 SEMTECH CORP. 652 MITCHELL ROAD NEWBURY PARK CA 91320
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