NCP690, NCP691, NCP692

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DEFINITIONS

Load Regulation

The change in output voltage for a change in output load

current at a constant temperature.

Dropout Voltage

The input/output differential at which the regulator output

no longer maintains regulation against further reductions in

input voltage. Measured, when the output drops 100 mV

below its nominal value. The junction temperature, load

current, and minimum input supply requirements affect the

dropout level.

Output Noise Voltage

This is the integrated value of the output noise over a

specified frequency range. Input voltage and output load

current are kept constant during the measurement. Results

are expressed in

Ground Current

Ground Current is the current that flows through the

ground pin when the regulator operates without a load on its

etc. It is actually the difference between the input current

(measured through the LDO input pin) and the output load

current. If the regulator has an input pin that reduces its

internal bias and shuts off the output (enable/disable

Line Regulation

The change in output voltage for a change in input voltage.

The measurement is made under conditions of low

dissipation or by using pulse techniques such that the

average junction temperature is not significantly affected.

Line Transient Response

Typical output voltage overshoot and undershoot

response when the input voltage is excited with a given

slope.

Load Transient Response

Typical output voltage overshoot and undershoot

response when the output current is excited with a given

slope between no−load and full−load conditions.

Thermal Protection

Internal thermal shutdown circuitry is provided to protect

the integrated circuit in the event that the maximum junction

temperature is exceeded. When activated at typically 175

°C,

the regulator turns off. This feature is provided to prevent

failures from accidental overheating.

Maximum Package Power Dissipation

The power dissipation level at which the junction

temperature reaches its maximum operating value.

APPLICATIONS INFORMATION

The NCP690 regulator is self−protected with internal

thermal shutdown and internal current limit. Typical

application circuit is shown in Figure 1.

A ceramic 10

mF capacitor is recommended and should be

connected close to the NCP690 package. Higher

capacitance and lower ESR will improve the overall line

transient response.

The NCP690 does not require a minimum Equivalent

Series Resistance (ESR) for the output capacitor. The

minimum output decoupling capacitor required for stability

is 1

mF. In order to improve the load transient response and

start up performance 10

mF capacitor is recommended. The

regulator is stable with ceramic chip as well as tantalum

capacitors. Larger values improve noise rejection and load

transient response.

No−Load Regulation Considerations

The required minimum 100

mA load current is assured by

the internal resistor divider network.

The NCP690 contain an overshoot clamp circuit to

improve transient response during a load current step

release. When output voltage exceeds the nominal by

approximately 20 mV, this circuit becomes active and

clamps the output from further voltage increase. Tying the

whenever the supply voltage is present,

Noise Decoupling

The NCP690 is a low noise regulator and needs no

external noise reduction capacitor. Unlike other low noise

regulators which require an external capacitor and have slow

startup times, the NCP690 operates without a noise

reduction capacitor, has a typical 50

ms turn−on time and

achieves a 50

100 kHz.

Enable Operation

The enable pin will turn the regulator on or off. The

threshold limits are covered in the electrical characteristics

table in this data sheet. The turn−on/turn−off transient

voltage being supplied to the enable pin should exceed a

slew rate of 10 mV/

ms to ensure correct operation. If the

enable function is not to be used then the pin should be

Adjustable Operation

The output voltage can be adjusted from 1 to 4 times the

typical 1.250 V regulation voltage by the use of resistor