CS8135
Definition of Terms
Dropout Voltage
The input-output voltage differential at which the circuit
ceases to regulate against further reduction in input volt-
age. Measured when the output voltage has dropped
100mV from the nominal value obtained at 14V input,
dropout voltage is dependent upon load current and junc-
tion temperature.
Input Voltage
The DC voltage applied to the input with respect to ground.
Input Output Differential
The voltage difference between the unregulated input
voltage and the regulated output voltage for which the
regulator will operate.
Line Regulation
The change in output voltage for a change in the input
voltage. The measurement is made under conditions of
low dissipation or by using pulse techniques such that the
average chip temperature is not significantly affected.
Load Regulation
The change in output voltage for a change in load current
at constant chip temperature.
Long Term Stability
Output voltage stability under accelerated life-test condi-
tions after 1000 hours with maximum rated voltage and
junction temperature.
Output Noise Voltage
The rms AC voltage at the output, with constant load and
no input ripple, measured over a specified frequency
range.
Quiescent Current
The part of the positive input current that does not con-
tribute to the positive load current. i.e., the regulator
ground lead current.
Ripple Rejection
The ratio of the peak-to-peak input ripple voltage to the
peak-to-peak output ripple voltage.
Temperature Stability of V
OUT
The percentage change in output voltage for a thermal
variation from room temperature to either temperature
extreme.
Current Limit
Peak current that can be delivered to the output.
Typical Circuit Waveform
60V
V
IN
14V
31V
3V
26V
14V
SWITCH
OPEN
CLOSED
5V
2.4V
OPEN
5V
0V
5V
5V
0V
V
OUT
1
0V
5V
RESET
V
OUT
2
0V
5V
5V
2.4V
5V
System
Condition
Turn
On
Load
Dump
Low V
IN
Line, Noise, Etc.
V
OUT1
Short
Circuit
Thermal
Shutdown
Turn
Off
*Reference Test & Application Circuit
Circuit Description
Standby Output
The CS8135 is equipped with two outputs. The second out-
put is intended for use in systems requiring standby mem-
ory circuits. While the high current regulator output can be
controlled with the RESET lead described below, the stand-
by output remains on under all conditions as long as suffi-
cient input voltage is applied to the IC. Thus, memory and
other circuits powered by this output remain unaffected by
positive line transients, thermal shutdown, etc.
The standby regulator circuit is designed so that the quies-
cent current to the IC is very low (<3mA) when the other
regulator output is off.
5
In applications where the standby output is not needed, it
may be disabled by connecting a resistor from the standby
output to the supply voltage. This eliminates the need for
a capacitor on the output to prevent unwanted oscilla-
tions. The value of the resistor depends upon the mini-
mum input voltage expected for a given system. Since the
standby output is shunted with an internal diode zener,
the current through the external resistor should be suffi-
cient to bias V
OUT2
up to this point. Approximately 60µA
will suffice, resulting in a 10k�½ external resistor for most
applications.
CHERRY [ CHERRY SEMICONDUCTOR CORPORATION ]
