CS8371 데이터 시트보기 (PDF) - Cherry semiconductor

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CS8371

8V/1A, 5V/250mA Dual Regulator with Independent Output Enables and NoCap™

Cherry semiconductor 

Applications Circuit

Control

C1*

0.1 mF

VIN

VOUT1

CS8371

ENABLE1

DISPLAY

8V

ENABLE2

Gnd

VOUT2

5V

Tuner IC

*C1 is required if regulator is far from power source filter.

Application Notes

With separate control of each output channel, the CS8371

is ideal for applications where each load must be switched

independently. In an automotive radio, the 8V output

drives the displays and tape drive motors while the 5V

output supplies the Tuner IC and memory.

Stability Considerations/NoCapª

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.

NoCapª is a Cherry 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 (>80dB) and large unity gain bandwidth

(>100kHz) while maintaining many of the characteristics

of a single-pole amplifier (large phase margin and no

overshoot).

NoCapª is ideally suited for slow switching or steady

loads. If the load displays large transient current require-

ments, 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 cause small signal oscillations at the output. This will

depend on the load conditions. With these types of loads,

a traditional output stage may be better suited for proper

operation.

Output 1 employs NoCapª. Refer to the plots in the

Typical Performance Characteristics section for appropri-

ate output capacitor selections for stability if an external

capacitor is required by the switching characteristics of the

load. Output 2 has a Darlington NPN-type output struc-

ture and is inherently stable with any type of capacitive

load or no capacitor at all.

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