CS8371
http://onsemi.com
8
DEFINITION OF TERMS
Dropout Voltage − The input−output voltage differential
at which the circuit ceases to regulate against further
reduction in input voltage. Measured when the output
voltage has dropped 100 mV from the nominal value
obtained at 14 V input, dropout voltage is dependent upon
load current and junction temperature.
Current Limit − Peak current that can be delivered to the
output.
Input Voltage − The DC voltage applied to the input
terminals 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 conditions 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 contribute to the positive load current.
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.
Figure 23. Applications Circuit
V
IN
GND
ENABLE
1
V
OUT1
V
OUT2
CS8371
Tuner IC
Control
C
1
*
0.1 mF
5.0 V
8.0 V
* C
1
is required if the regulator is far from the power source filter.
ENABLE
2
APPLICATION NOTES
With seperate control of each output channel, the CS8371
is ideal for applications where each load must be switched
independently. In an automotive radio, the 8.0 V output
drives the displays and tape drive motors while the 5.0 V
output supplies the Tuner IC and memory.
Stability Considerations/NOCAP
Normally a low dropout or quasi−low dropout regulator
(or any type requiring a slow lateral PNP in the control loop)
necessitates a large external compensation capacitor at the
output of the IC. The external capacitor is also used to curtail
overshoot, determine startup delay time and load transient
response.
Traditional LDO regulators typically have low unity gain
bandwidth, display overshoot and poor ripple rejection.
Compensation is also an issue because the high frequency
load capacitor value, ESR (Equivalent Series Resistance)
and board layout parasitics all can create oscillations if not
properly accounted for.
NOCAP is an ON Semiconductor exclusive output stage
which internally compensates the LDO regulator over
temperature, load and line variations without the need for
an expensive external capacitor. It incorporates high gain
(>80 dB) and large unity gain bandwidth (>100 kHz) while
maintaining many of the characteristics of a single−pole
amplifier (large phase margin and no overshoot).
NOCAP is ideally suited for slow switching or steady
loads. If the load displays large transient current
requirements, such as with high frequency microprocessors,
an output storage capacitor may be needed. Some large
capacitor and small capacitor ESR values at the output may
