specifications applying to the over full operating temperature range.
Note 1: Low duty cycle pulse testing with Kelvin connections are required to order to maintain accurate data.
Note 2: Dropout voltage is defined as the minimum differential between V
IN
and V
OUT
or V
CTRL
and V
OUT
required to maintain regulation at V
OUT
99% Nominal V
OUT.
Note 3: V
REF
is measured across Adjust pin to Sense pin.
Date: 5/12/04
SPX1582
PIN DESCRIPTION
1.
2.
3.
4.
5.
Sense = Allows Kelvin sense of V
OUT
at the load. (Positive side of the reference voltage of the
device).
ADJ = Negative side of the reference voltage for the device. Adding a small bypass capacitor
from the ADJ pin to ground will improve the transient response.
V
OUT
= Power output of the device.
V
CTRL
= Supply pin for the control circuitry of the device. The current flow into this pin will be
about 1% of the output current. V
CTRL
must be between 1.0V and 1.3V greater than the output
voltage for the device to regulate.
V
IN
= Output load current is supplied through this pin. V
IN
must be between 0.1V and 0.8V
greater than the output voltage for the device to regulate.
BLOCK DIAGRAM
(4) V
CTRL
S.O.A
V
IN
(5)
CURRENT
LIMIT
AMPLIFIER
LIMIT
SENSE
V
OUT
(3)
THERMAL OVERLOAD
SENSE (1)
VOLTAGE
REGULATION
AMPLIFIER
V
REF
ADJ (2)
APPLICATIONS NOTES
The SPX1582 is designed as a high performance and low cost
solution for application requiring a lower dropout than
traditional NPN regulators.
The SPX1582 uses a separate input voltage V
CTRL
(V
CTRL
≥
V
OUT
+ 1.3V) to minimize the dropout voltage. This allows the
2.5V power for the load to come from a 3.3V system supply.
As added benefit this will reduce the heat dissipation, and
lower heatsink and cooling fan cost. A typical application
would use 5V for Vin and 3.3V for V
CTRL
from a motherboard
power supply to provide a nominal 2.5V output. Using the
sense pin allows to Kelvin measure the output, reducing
resistive-associated errors.
The SPX1582 can power the 2.5V core voltage for
microprocessors such as Pentium, P55C, AMD5k86
and K6 and the IBM PowerPC 603EV and 604EV
processors.
*The reduction of heat dissipation is a result of the increase of the regulator
efficiency (efficiency = V
OUT
/ V
IN
).
Adjustable Regulator Design
1.25V reference voltage is being developed between the
SENSE pin and the ADJ pin of the SPX1582. Adding two
external resistors (see fig 1.) will allow setting the output
voltage from 1.25V to 6V. R
1
is chosen so that this current is
specified minimum load current of 10mA. R
2
is given by the
formula: V
OUT
= V
REF
(1+ R
2
/R
1
) + I
ADJ
(R
2
). The current
flowing from the ADJ pin is typically 50µA. This ADJ pin
contributes to the final VOUT but is usually neglected.
Connecting the sense pin to the top of the resistor divider will
improve load regulation.
Lowering Noise
Using the SENSE pin to Kelvin the load will increase accuracy
of the output voltage during load regulation. For the fixed
voltage devices, adding a capacitor at the GND pin will
improve transient response. This capacitor is chosen in the
range of 1µF to 0.1µF and will depend on the amount of
output capacitance in the system.
Date: 5/12/04
SPX1582
TYPICAL APPLICATION
Fig. 1 Adjustable Regulator
3.3V
V
IN
5V
V
CTRL
C1
330uF
V
IN
V
OUT
SPX1582
V
CTRL
ADJ
C2
10uF
2.5V
V
OUT
SENSE
R1
124
Ω
C4
2 X 330uF
C3
.033uF
R2
124
Ω
(1) V
CTRL
needed when V
IN
< 5V.
(2) V
OUT
= V
REF
(1 + R2/ R1) + I
ADJ
R2.
(3) V
REF
is measured across adjust to sense.
Fig.2 Typical Fixed Regulator
3.3V
V
IN
C1
5V
V
CTRL
330uF
V
IN
V
OUT
SPX1582
2.5V
V
OUT
V
CTRL
GND
C2
10uF
SENSE
C4
2 X 330uF
(1) V
CTRL
is needed when V
IN
<5V.
Date: 5/12/04
SPX1582
ORDERING INFORMATION
Ordering
No.
SPX1582U
SPX1582U-2.5
SPX1582U-2.8
SPX1582U-3.3
SPX1582T
SPX1582T-2.5
SPX1582T-2.8
SPX1582T-3.3
Precision
0.6%
0.6%
0.6%
0.6%
0.6%
0.6%
0.6%
0.6%
Output Voltages
Adj
2.5V
2.8V
3.3V
Adj
2.5V
2.8V
3.3V
Packages
5
Lead TO-220
5
Lead TO-220
5
Lead TO-220
5
Lead TO-220
5
Lead TO-263
5
Lead TO-263
5
Lead TO-263
5
Lead TO-263
Corporation
ANALOG
EXCELLENCE
Sipex Corporation
Headquarters and Main Offices:
233 South Hillview Drive
Milpitas, CA 95035
TEL: (408) 935-7600
FAX: (408) 934-7500
Sipex Corporation reserves the right to make changes to any products described herein. Sipex does not assume any liability arising out of the application or use of any product or circuit described
hereing; neither does it convey any license under its patent rights nor the rights of others.
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