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SI-3025ZF
High-Current, Low-Dropout, 2.5 V Regulator
Designed to meet the high-current requirements in industrial and
consumer applications; embedded core, memory, or logic supplies; TVs,
VCRs, and office equipment, the SI-3025ZF voltage regulator offers the
reduced dropout voltage and low quiescent current essential for im-
proved efficiency. This device delivers a regulated output at up to 3 A.
Integrated thermal and overcurrent protection enhance overall system
reliability. Devices with an adjustable 1.2 ~ 5 V output or a 3.3 V fixed
output are also available.
Quiescent current does not increase significantly as the dropout
voltage is approached, an ideal feature in standby/resume power systems
where data integrity is crucial. Regulator accuracy and excellent
temperature characteristics are provided by a bandgap reference. An
LS-TTL/CMOS-compatible input gives the designer complete control
over power up, standby, or power down. A pnp pass element provides a
dropout voltage of less than 700 mV at 3 A of load current. Low output
voltages eliminate the need for expensive PWM buck converters. The
low dropout voltage permits more efficient regulation before output
regulation is lost.
This device is supplied in a fully molded TO-220-style 5-lead
flange-mounted , high power, isolated plastic package. A similar device
in a lower-power surface-mount plastic package is the SI-3025ZD.
FEATURES
■
3 A Output Current at 2.5 V
■
0.7 V Maximum Dropout Voltage at I
O
= 3 A
■
1 µA Maximum Standby Current
■
Remote Voltage Sensing
■
Foldback Current Limiting
■
Thermal Protection
APPLICATIONS
■
TVs, VCRs, Electronic Games
■
Embedded Core, Memory, or Logic Supplies
■
Printers and Other Office Equipment
■
Industrial Machinery
■
Secondary-Side Stabilization of Multi-Output SMPS
Data Sheet
27468.27*
ABSOLUTE MAXIMUM RATINGS
Input Voltage, V
I
. . . . . . . . . . . . .
10 V
Output Current, I
O
. . . . . . . . . . . . .
3 A*
Enable Input Voltage, V
E
. . . . . . . .
6V
Junction Temperature, T
J
. . . .
+125°C
Storage Temperature Range,
T
S
. . . . . . . . . . . .
-40°C to +125°C
* Output current rating is limited by input
voltage, duty cycle, and ambient tempera-
ture. Under any set of conditions, do not
exceed a junction temperature of +125°C.
Always order by complete part number, e.g.,
SI-3025ZF
.
Sanken Power Devices
from Allegro MicroSystems
SI-3025ZF
High-Current,
Low-Dropout,
2.5 V Regulator
FUNCTIONAL BLOCK DIAGRAM
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Allowable Package Power Dissipation
Recommended Operating Conditions
Min
—
0
-20
Max
6
3
+100
Units
V
A
°C
DC Input Voltage
DC Output Current
Operating Junction Temp.
For the availability of parts meeting -40°C requirements,
contact Allegro’s Sales Representative.
This data sheet is based on Sanken data sheet SSJ-02578
2
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036
Copyright © 2004, 2005 Allegro MicroSystems, Inc.
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ELECTRICAL CHARACTERISTICS
at T
A
= +25°C, V
E
= 2 V (unless otherwise noted).
SI-3025ZF
High-Current,
Low-Dropout,
2.5 V Regulator
Limits
Characteristic
Output Voltage
Symbol
V
O
V
O(off)
Output Volt. Temp. Coeff.
Output Short-Circuit Current
Line Regulation
Load Regulation
Dropout Voltage
Ground Terminal Current
Test Conditions
V
I
= 3.3 V, I
O
= 10 mA
V
E
= 0 V
0°C
≤
T
J
≤
100°C
V
I
= 3.3 V, see note
V
I
= 3.0 ~ 5.0 V, I
O
= 10 mA
V
I
= 3.3 V, I
O
= 0 A ~ 3.0 A
I
O
= 3.0 A
V
I
= 3.3 V, I
O
= 0 mA, V
E
= 2.0 V
V
I
= 3.3 V, V
E
= 0 V
Enable Input Voltage
V
EH
V
EL
Enable Input Current
I
EH
I
EL
Ripple Rejection Ratio
Thermal Shutdown
PSRR
T
J
Output ON
Output OFF
V
E
= 2.7 V
V
E
= 0 V
V
I
= 3.3 V, 100 Hz
≤
f
≤
120 Hz
Min.
2.45
—
—
3.2
—
—
—
—
—
2.0
—
—
—
—
135
Typ.
2.50
—
±0.3
—
—
—
—
1.0
—
—
—
—
0
60
152
Max.
2.55
0.5
—
—
10
40
0.7
1.5
1.0
—
0.8
100
-5.0
—
—
Units
V
V
mV/°C
A
mV
mV
V
mA
µA
V
V
µA
µA
dB
°C
a
VO
I
OM
∆V
O(∆VI)
∆V
O(∆IO)
V
Imin
- V
O
I
GND
Typical values are given for circuit design information only.
Note: Output short-circuit current is at point where output voltage has decreased 5% below V
O(nom)
.
www.allegromicro.com
3
SI-3025ZF
High-Current,
Low-Dropout,
2.5 V Regulator
TYPICAL CHARACTERISTICS
(T
A
= 25°C)
Dropout Voltage
Low-Voltage Behavior
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GND Pin Current
Line Regulation
Load Regulation
Overcurrent Protection
ENABLE Control Voltage
ENABLE Control Current
Thermal Protection
4
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036
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APPLICATIONS INFORMATION
Input Capacitor
(C
I
, approximately 10 µF). This is
necessary either when the input line includes inductance or
when the wiring is long.
Output Capacitor
(C
O
, > 47 µF). This device is not
designed for a use with a very low ESR output capacitor
such as a ceramic capacitor. Output oscillation may occur
with that kind of capacitor.
Determination of DC Input Voltage.
The minimum
input voltage V
I
(min) should be higher than the sum of the
fixed output voltage and the maximum rated dropout
voltage.
Increased Output Voltage.
The output voltage (V
O
)
may be increased by inserting a resistor (R
EXT
) between
SENSE and OUTPUT. The current flowing into SENSE is
typically 90 µA ±30%. To minimize the effect of I
SENSE
and temperature on R
EXT
, it is recommended that a 6.8 kΩ
resistor be added between SENSE and GND to increase the
current in R
EXT
. The value of R
EXT
is then
6
R
EXT
= (V
O
– 2.5) × 10 /458
Overcurrent Protection.
The SI-3000ZD series has a
built-in fold-back type overcurrent protection circuit, which
limits the output current at a start-up mode. It thus cannot
be used in applications that require current at the start-up
mode such as:
(1) constant-current load,
(2) power supply with positive and negative outputs to
common load (a center-tap type power supply), or
(3) raising the output voltage by putting a diode or a
resistor between the device ground and system ground.
Thermal Protection.
Circuitry turns off the pass
transistor when the junction temperature rises above 135°C.
It is intended only to protect the device from failures due to
excessive junction temperatures and should not imply that
output short circuits or continuous overloads are permitted.
SI-3025ZF
High-Current,
Low-Dropout,
2.5 V Regulator
Heat Radiation and Reliability.
The reliability of the
IC is directly related to the junction temperature (T
J
) in its
operation. Accordingly, careful consideration should be
given to heat dissipation. The graph on page 2 illustrates
the effect of thermal resistance on the allowable package
power dissipation.
When mounting to a heat sink, apply silicone grease (Shin-
Etsu Chemical G746, Dow Corning Toray Silicone SC102,
or Toshiba Silicone SY6260). Recommended mounting
hardware torque: 0.588 ~ 0.686 Nm or 6.0 ~ 7.0 kgf•cm
(4.34 ~ 5.06 lbf•ft).
The junction temperature (T
J
) can be determined from
either of the following equations:
T
J
= (P
D
× R
θJA
) + T
A
or
T
J
= (P
D
× R
θJC
) + T
C
where P
D
= I
O
× (V
I
– V
O
) and
R
θJC
= 5°C/W.
Parallel Operation.
Parallel operation to increase load
current is not permitted.
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5
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