Si91861
Vishay Siliconix
400-mA Smart Regulator for Network Interface Card
FEATURES
Single Fixed 3.3-V Output
Linear Regulator for 5-V Power Input
Auxilliary Input Can Be Bypassed
Automatically Switches Between Linear Regulator
and Bypass Mode
D
Linear Regulator: 3.3-V
"3%
Output at 400-mA
Current; 600-mA Peak Output Current
D
Low Bypass Switch Voltage-Drop: <55-mV at
150 mA
D
Built-in Short Circuit and Thermal Shutdown
Protection
D
D
D
D
D
Low Supply Current
D
SOIC-8 Package
APPLICATIONS
D
D
D
D
Network Interface Cards (NIC)
PCMCIA Cards
Cardbus
Desktop Computers/Workstations
DESCRIPTION
The Si91861 provides a constant 3.3-V output with multiple
inputs. This function is required in many power interface
applications, such as the Network Interface Card (NIC). The
Si91861 is offered in small SOIC-8 package with up to 2-W
power handling capability. The complete application circuit
uses only three external components.
5 V
IN
> 3.3 V
AUX
, where the selection is done internally and
automatically by the Si91861. The power handling capability
is as such as to carry at least 400-mA continuous load current
for any power input condition.
In order to satisfy the stringent ambient temperature
requirements in many applications, the Si91861 is rated for the
industrial temperature range of
−40_C
to 85_C.
The Si91861 is available in both standard and lead (Pb)-free
packages.
The linear regulator steps down from the 5-V supply (5 V
IN
)
to 3.3 V. A 200-mΩ bypass switch is integrated to connect the
3.3-V
AUX
input to the output. The power drawn priority is
FUNCTIONAL BLOCK DIAGRAM
Si91861
5 V
IN
Regulator
and
Control
3.3 V
OUT
3.3 V
AUX
GND
Document Number: 71637
S-40702—Rev. B, 19-Apr-04
www.vishay.com
1
Si91861
Vishay Siliconix
ABSOLUTE MAXIMUM RATINGS
Pin 2, 4 Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
−0.3
V to 6 V
Linear Regulator Output Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 600 mA
Bypass Switch Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 600 mA
Maximum Junction Temperature, T
J(max)
. . . . . . . . . . . . . . . . . . . . . . . . 150_C
Storage Temperature, T
STG
. . . . . . . . . . . . . . . . . . . . . . . . . .
−55_C
to 150_C
ESD (Human Body Model) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 kV
Package Power Dissipation
b
P
D
. . . . . . . . . . . . . . . . . . . . . . . . 2W (internally limited via thermal shutdown)
Thermal Impedance (q
JA
)
a
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62.5_C/W
Notes
a. Device mounted with all leads soldered or welded to PC board.
b. Derate 16 mW/_C above T
A
= 25_C
Stresses beyond those listed under “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 for extended periods may affect device reliability.
RECOMMENDED OPERATING RANGE
5-V
IN
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.5 V to 5.5 V
3.3-V
AUX
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 V to 3.6 V
3.3 V
OUT
Loading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 mA to 400 mA
Operating Ambient Temperature, T
A
. . . . . . . . . . . . . . . . . . . .
−40_C
to 85_C
SPECIFICATIONS
Test Conditions
Unless Otherwise Specified
Parameter
Regulator Mode
Output Voltage (Regulator)
5 V
IN
Select
Ground Pin Current
In Regulator Mode
d
Peak Output Current (Regulator)
Output Noise Voltage (Regulator)
I
GND
I
O
e
N
D3.3
D3
3 V
OUT
/
D5
V
IN
DV
O(line)
DV
O(load)
t
ON
T
J(sd)
T
HYST
I
SC
3.3 V
OUT
= 0 V
V
O(reg)
0 mA < I
OUT
< 400 mA, 5 V
IN
u
4.5 V
Rising Edge of Hysteresis
I
O
= 0 mA
I
O
= 400 mA
t
PW
= 2 ms
BW = 50 Hz to100 kHz, I
OUT
= 150 mA
1 kHz
Ripple Rejection (Regulator)
pp
j
( g
)
I
OUT
= 150 mA
10 kHz
100 kHz
V
IN
= 4.5 V
@@
5.5 V
t
R
/t
F
= 2
ms,
I
OUT
= 150 mA
I
OUT
: 1 mA to 150 mA, t
R
/t
F
= 2
ms
Threshold
Hysteresis
Full
Full
Full
Full
Full
Full
Room
Room
Room
Room
Room
Room
Room
Full
Full
Room
600
300
60
40
30
10
20
15
165
20
900
mA
ms
_C
C
mV
dB
mV
rms
3.201
3.3
4.30
230
0.3
0.7
0.8
1.6
mA
3.399
4.475
V
mV
Limits
−40
to 85_C
Symbol
5 V
IN
= 5 V, 3.3 V
AUX
= 3 3 V
V 33
3.3
I
OUT
= 1 mA, C
IN
= 4.7
mF,
C
OUT
= 2.2
mF
Temp
a
Min
b
Typ
c
Max
b
Unit
Dynamic Line Regulation
Dynamic Load Regulation
V
OUT
Turn-On-Time
Thermal Shutdown Junction
Temperature
Thermal Hysteresis
Short Circuit Current
Bypass Mode (5 V
IN
= GND)
Output Voltage
Bypass Switch On-Resistance
Ground Current
d
V
O(BP)
r
DS(on)
I
GND
0 mA < I
OUT
< 150 mA
3.0 V
v
V
AUX
v
3.6 V
0 mA < I
OUT
< 400 mA
Full
Full
Full
3.247
0.2
200
0.35
400
V
W
mA
Notes
a. Room = 25_C, Full =
−40
to 85_C.
b. The algebraic convention whereby the most negative value is a minimum and the most positive a maximum.
c. Typical values are for DESIGN AID ONLY, not guaranteed nor subject to production testing. Typical values at 25_C ambient.
d. Ground pin current includes the IC supply current and the current to drive the linear regulator or bypass switch.
www.vishay.com
Document Number: 71637
S-40702—Rev. B, 19-Apr-04
2
Si91861
Vishay Siliconix
TIMING WAVEFORMS
5V
t
ON
5 V
IN
0.95 V
O(reg)
3.3 V
OUT
FIGURE 1.
Timing Diagram
PIN CONFIGURATION
SO-8
N.C.
5 V
IN
3.3 V
OUT
3.3 V
AUX
1
2
3
4
Top View
8
7
6
5
GND
GND
GND
GND
PIN DESCRIPTION
Pin Number
1
2
3
4
5, 6, 7, 8
Name
N.C.
5 V
IN
3.3 V
OUT
3.3 V
AUX
GND
Function
Not connected. No effect to device operation
Power input for the Regulator
Output 3.3 V
Power input for the bypass function
Ground
Document Number: 71637
S-40702—Rev. B, 19-Apr-04
www.vishay.com
3
Si91861
Vishay Siliconix
ORDERING INFORMATION
Part Number
Si91861DY-T1
Si91861DY-T1—E3
Si91861DY
−40
to 85_C
Temperature Range
Package
Tape and Reel
Bulk
Eval Kit
Si91861DB
Temperature Range
−40
to 85_C
Board Type
Surface Mount
TYPICAL CHARACTERISTICS
1.0
Ground Current vs Temperature (5 V
IN
)
I
OUT
= 600 mA
1.0
Ground Current vs Input Voltage (5 V
IN
)
I
OUT
= 0
0.8
Ground Current (mA)
Ground Current (mA)
I
OUT
= 400 mA
0.6
I
OUT
= 200 mA
0.8
3.3 V
AUX
= 0 V
0.6
0.4
I
OUT
= 0 mA
0.4
0.2
5 V
IN
= 5 V
0.0
−40
0.2
0.0
−20
0
20
40
60
80
100
0
1
2
3
Input Voltage (V)
4
5
6
Temperature (
o
C)
0.35
ON-Resistance vs 3.3 V
AUX
Input Voltage
0.8
Ground Current vs 3.3 V
AUX
Input Voltage
0.30
Ground Current (mA)
0.6
Resistance (Ω)
0.25
85_C
25_C
−40_C
0.4
5 V
IN
=
5 V
0.20
0.15
0.2
5 V
IN
=0
V
0.10
3.0
3.1
3.2
3.3
3.4
3.5
3.6
0.0
0.0
0.6
1.2
1.8
2.4
3.0
3.6
3.3 V
AUX
Input Voltage (V)
3.3 V
AUX
Input Voltage (V)
www.vishay.com
4
Document Number: 71637
S-40702—Rev. B, 19-Apr-04
Si91861
Vishay Siliconix
TYPICAL WAVEFORMS
Load Transient Response-1
Load Transient Response-2
V
OUT
= 10 mV/div
V
OUT
= 10 mV/div
I
OUT
= 100 mA/div
I
OUT
= 100 mA/div
Input = 5 V
IN
I
OUT
= 1 to 150 mA
t
rise
= 2
msec
M 5.00
ms
Input = 5 V
IN
I
OUT
= 150 to 1 mA
t
FALL
= 2
msec
M 5.00
ms
Load Transient Response-3
Load Transient Response-4
V
OUT
= 50 mV/div
V
OUT
= 50 mV/div
I
OUT
= 200 mA/div
I
OUT
= 200 mA/div
Input = 5 V
IN
I
OUT
= 0 to 400 mA
t
rise
= 2
msec
M 5.00
ms
Input = 5 V
IN
I
OUT
= 400 to 0 mA
t
FALL
= 2
msec
M 5.00
ms
5-V
IN
Power Up
5-V
IN
Power Down
3.3 V
OUT
(100 mV/div)
3.3 V
OUT
(100 mV/div)
5 V
IN
500 mV/div (offset = 4.3 V)
5 V
IN
500 mV/div (offset = 4.2 V)
3.3 V
AUX
= 0 V
I
OUT
= 400 mA
M 5.00
ms
3.3 V
AUX
= 0 V
I
OUT
= 400 mA
M 5.00
ms
Document Number: 71637
S-40702—Rev. B, 19-Apr-04
www.vishay.com
5
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