LT1573 Datasheet, PDF (1/16 Pages) Linear Technology – Low Dropout PNP Regulator Driver

FEATURES
s _{Low Cost Solution for High Current, Low Dropout}
Regulators
s _{Fast Transient Response Needs Much Less}
Bulk Capacitance
s _{Latching Overload Protection Minimizes}
Heat Sink Size
s _{Precision Output Voltage (1%)}
s _{Single Supply Operation: VIN = 2.8V to 10V}
s _{Small Surface Mount Package}
s _{Capable of Very Low Dropout Voltage (<0.2V)}
s _{Fixed or Adjustable Outputs}
s _Shutdown
U
APPLICATIO S
s _{3.3V to 2.5V Regulators}
s _{Microprocessor Power Sources}
s _{Post Regulator for Switching Supplies}
s _{High Efficiency Linear Regulators}
s _{Ultralow Dropout Regulators}
s _{Low Voltage Linear Regulators}
, LTC and LT are registered trademarks of Linear Technology Corporation.
LT1573
Low Dropout
PNP Regulator Driver
DESCRIPTIO
The LT ^®1573 is a regulator driver IC designed to provide
a low cost solution for applications requiring high current,
low dropout and fast transient response. When combined
with an external PNP power transistor, this device pro-
vides load current up to 5A with dropout voltages as low
as 0.35V. The LT1573 circuitry is designed for extremely
fast transient response. This greatly reduces bulk storage
capacitance when the regulator is used in applications
with fast, high current load transients.
To keep cost and complexity low, the LT1573 uses a new
time-delayed latching overcurrent protection technique
that requires no external current sense resistor. Base drive
is limited for instantaneous protection, and a time-delayed
latch protects the regulator from continuous short
circuits.
The LT1573 is available as an adjustable regulator with an
output range of 1.27V to 6.8V and with fixed output
voltages of 2.5V, 2.8V and 3.3V. Output accuracy is better
than 1% to meet the critical regulation requirement of fast
microprocessors. A special 8-pin, fused-lead surface mount
package is used to minimize regulator footprint and pro-
vide adequate heat sinking.
TYPICAL APPLICATIO
C_C
100pF
R_C
1k
FB
COMP
+
C_TIME
V_IN
5V
LATCH
V_OUT
LT1573
SHDN
V_IN
GND
DRIVE
C_IN
100µF
TANT
R_{D RB}
24Ω _50Ω
Q_OUT
MOTOROLA
D45H11
+
C_OUT1
1µF
+
C_OUT2
R1
1.6k
CER
220µF
× 24
TANT
R2
1k
LOAD
V_OUT = 1.265V (1 + R1/R2)
FOR T < 45°C, C_OUT1 = 24 × 1µF Y5V CERAMIC SURFACE MOUNT CAPACITORS.
FOR T > 45°C, C_OUT1 = 24 × 1µF X7R CERAMIC SURFACE MOUNT CAPACITORS.
PLACE C_OUT1 IN THE MICROPROCESSOR SOCKET CAVITY
Figure 1. 3.3V, 5A Microprocessor Supply
V_OUT
3.3V
GND
1573 F01
Transient Response for
0.2A to 5A Output Load Step
50mV/DIV
2.5A/DIV
10µs/DIV
1573 F01a
1