CS8128 Datasheet, PDF (1/8 Pages) Cherry Semiconductor Corporation – 5V Linear Controller/Driver

CS8128
5V Linear Controller/Driver
Description
Features
The CS8128 contains all the necessary
control circuitry to implement a 5V lin-
ear regulator. An external pass device is
used to produce superior performance
compared to conventional monolithic
regulators. The CS8128 with a TIP42
PNP transistor typically provides a
100mV dropout voltage at 500mA,
increasing to 350mV at 3A. Quiescent
current at 500mA is only 5mA.
Monolithic regulators cannot approach
these figures because their power tran-
sistors do not provide the high beta and
excellent saturation characteristics at
high currents. The CS8128 is compatible
with a wide variety of external transis-
tors, allowing flexibility for thermal,
space, and cost management.
The CS8128 includes thermal shutdown
and externally programmable current
limit and over-voltage shutdown, mak-
ing it suitable for use in automotive and
switching regulator post regulator appli-
cations. An optional external RC filter
added to the CS8128 supply lead pro-
vides EMC hardening in addition to the
on-chip EMC hardening. The SENSE
lead allows remote sensing of the output
voltage for improved regulation.
An active microprocessor RESET func-
tion is included on-chip with externally
programmable delay time. During
power-up, or after detection of any error
in the regulated output, the RESET lead
will remain in the low state for the dura-
tion of the delay. Types of errors include
short circuit, low input voltage, over-
voltage shutdown, thermal shutdown,
or others that cause the output to
become unregulated. This function is
independent of the input voltage and
will function correctly with an output
voltage as low as 1V. Hysteresis is
included in both the reset and delay
comparators for noise immunity and to
prevent oscillations. A latching dis-
charge circuit is used to discharge the
delay capacitor, even when triggered by
a relatively short fault condition. This
circuit improves upon the commonly
used SCR structure by providing
improved noise immunity and full
capacitor discharge (0.2V typ).
Block Diagram
Pwr Gnd
Ref Gnd
V_IN
Delay
IC
Power
Gnd
IC
Reference
Gnd
PRE-
REGULATOR
Regulated Supply
for Circuit Bias
10µA
Delay
Current
Latching
Discharge
QS
R
-
+
V_dis
Over
Voltage
Shutdown
Thermal
Shutdown
Bandgap
Reference _1.25V
Error
Amp
-
Reset
Comparator
Delay
- ^Comparator
+
SHUTDOWN
V_OUT
Sense
RESET
s Externally Set Delay for
Reset
s 60V Load Dump
Protection
s Internal Thermal
Overload Protection
s 3% Output Accuracy
s Active RESET
s Noise Immunity
s On Chip EMC Hardening
Protection Incorporated
s Externally Set Current
Limit
s Externally Set
Overvoltage Shutdown
Package Options
8 Lead SO Narrow
V_IN 1
Sense 2
Delay 3
RESET 4
8 V_OUT
7 Pwr Gnd
6 SHUTDOWN
5 Ref Gnd
December, 2001 - Rev. 7
ON Semiconductor
2000 South County Trail, East Greenwich, RI 02818
Tel: (401)885–3600 Fax: (401)885–5786
N. American Technical Support: 800-282-9855
Web Site: www.cherry–semi.com
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