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NCP600

High Performance Low-Power, LDO Regulator with Enable

ON Semiconductor 

NCP600

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 2% below its

nominal. The junction temperature, load current, and

minimum input supply requirements affect the dropout level.

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.

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 mVrms or nV/√Hz.

Disable and Ground Current

Ground Current (IGND) is the current that flows through

the ground pin when the regulator operates with a load on its

output. This consists of internal IC operation, bias, 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 function), this term

is called the disable current (IDIS).

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 NCP600 series regulator is self−protected with

internal thermal shutdown and internal current limit. Typical

application circuits are shown in Figures 4 and 5.

Input Decoupling (Cin)

A ceramic or tantalum 1.0 mF capacitor is recommended

and should be connected close to the NCP600 package.

Higher capacitance and lower ESR will improve the overall

line transient response.

Output Decoupling (Cout)

The NCP600 is a stable component and does not require

a minimum Equivalent Series Resistance (ESR) for the

output capacitor. The minimum output decoupling value is

1.0 mF and can be augmented to fulfill stringent load

transient requirements. The regulator works with ceramic

chip capacitors as well as tantalum devices. Larger values

improve noise rejection and load regulation transient

response. Figure 30 shows the stability region for a range of

operating conditions and ESR values.

No−Load Regulation Considerations

The NCP600 adjustable regulator will operate properly

under conditions where the only load current is through the

resistor divider that sets the output voltage. However, in the

case where the NCP600 is configured to provide a 1.250 V

output, there is no resistor divider. If the part is enabled

under no−load conditions, leakage current through the pass

transistor at junction temperatures above 85°C can approach

several microamps, especially as junction temperature

approaches 150°C. If this leakage current is not directed into

a load, the output voltage will rise up to a level

approximately 20 mV above nominal.

The NCP600 contains 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

ENABLE pin to Vin will ensure that the part is active

whenever the supply voltage is present, thus guaranteeing

that the clamp circuit is active whenever leakage current is

present.

When the NCP600 adjustable regulator is disabled, the

overshoot clamp circuit becomes inactive and the pass

transistor leakage will charge any capacitance on Vout. If no

load is present, the output can charge up to within a few

millivolts of Vin. In most applications, the load will present

some impedance to Vout such that the output voltage will be

inherently clamped at a safe level. A minimum load of

10 mA is recommended.

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