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G916

300mA High PSRR, Low Noise, LDO Regulators

Global Mixed-mode Technology Inc 

Global Mixed-mode Technology Inc.

G916

＋

－ BATTERY CIN

1µF

IN

OUT

G916

SET

SHDN

GND

mount device, heat sinking is accomplished by using

OUTPUT

VOLTAGE

the heat spreading capabilities of the PC board and its

copper traces. In the case of a SOT-23-5 package, the

thermal resistance is typically 240°C/Watt. (See Rec-

ommended Minimum Footprint). Refer to Figure 3a &

R1

3b is the G916 valid operating region (Safe Operating

Area) & refer to Figure 4 is maximum power dissipa-

RL

R2

COUT

1µF

tion of SOT-23-5.

The die attachment area of the G916’s lead frame is

connected to pin 2, which is the GND pin. Therefore,

the GND pin of G916 can carry away the heat of the

G916 die very effectively. To improve the maximum

power providing capability, connect the GND pin to

ground using a large ground plane near the GND pin.

Figure 2. Adjustable Output Using External

Feedback Resistors

Over Current Protection

The G916 uses a current sense-resistor to monitor the

output current. A portion of the PMOS output transis-

tor’s current is mirrored to a resistor such that the

voltage across this resistor is proportional to the output

current. Once the output current exceeds limit thresh-

old, G916 would be protected with a limited output

current. Further more, when the output is short to

ground, the output current would be folded-back to a

less limit.

Over Temperature Protection

To prevent abnormal temperature from occurring, the

G916 has a built-in temperature monitoring circuit.

When it detects the temperature is above 145°C, the

output transistor is turned off. When the IC is cooled

down to below 120°C, the output is turned on again. In

this way, the G916 will be protected against abnormal

junction temperature during operation.

Shutdown Mode

When the SHDN pin is connected a logic low voltage,

the G916 enters shutdown mode. All the analog cir-

cuits are turned off completely, which reduces the

current consumption to only the leakage current. The

G916 output pass transistor would get into high im-

pedance level. There is an internal discharge path to

help to shorten discharge delay time.

Operating Region and Power Dissipation

Since the G916 is a linear regulator, its power dissipa-

tion is always given by P = IOUT (VIN – VOUT). The

maximum power dissipation is given by:

PD(MAX) = (TJ–TA) /θJA,=(150°C-25°C)/240°C/W = 520mW

Where (TJ–TA) is the temperature difference the G916

die and the ambient air,θJA, is the thermal resistance

of the chosen package to the ambient air. For surface

Applications Information

Capacitor Selection and Regulator Stability

Normally, use a 1µF capacitor on the input and a 1µF

capacitor on the output of the G916. Larger input ca-

pacitor values and lower ESR provide better sup-

ply-noise rejection and transient response. A higher-

value input capacitor (10µF) may be necessary if large,

fast transients are anticipated and the device is lo-

cated several inches from the power source.

Power-Supply Rejection and Operation from

Sources Other than Batteries

The G916 is designed to deliver low dropout voltages

and low quiescent currents in battery powered sys-

tems. Power-supply rejection is 65dB at low frequen-

cies. As the frequency increases above 20kHz, the

output capacitor is the major contributor to the rejec-

tion of power-supply noise.

When operating from sources other than batteries,

improve supply-noise rejection and transient response

by increasing the values of the input and output ca-

pacitors, and using passive filtering techniques.

Load Transient Considerations

The G916 load-transient response graphs show two

components of the output response: a DC shift of the

output voltage due to the different load currents, and

the transient response. Typical overshoot for step

changes in the load current from 10mA to 300mA is

8mV. Increasing the output capacitor's value and de-

creasing its ESR attenuates transient spikes.

Input-Output (Dropout) Voltage

A regulator's minimum input-output voltage differential

(or dropout voltage) determines the lowest usable sup-

ply voltage. In battery-powered systems, this will de-

termine the useful end-of-life battery voltage. Because

the G916 use a P-channel MOSFET pass transistor,

their dropout voltage is a function of RDS(ON) multiplied

by the load current.

Ver: 1.7

Jan 25, 2006

TEL: 886-3-5788833

http://www.gmt.com.tw

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