LM39100 데이터 시트보기 (PDF) - HTC Korea

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LM39100

1A Low-Voltage Low-Dropout Regulator

HTC Korea 

1A Low-Voltage Low-Dropout Regulator LM39100/39101/39102

Enable Input

The LM39101 and LM39102 versions feature an active-high enable input (EN) that allows on-off control of the

regulator. Current drain reduces to “zero” when the device is shutdown, with only micro amperes of leakage

current. The EN input has TTL/CMOS compatible thresholds for simple logic interfacing. EN may be directly

tied to VIN and pulled up to the maximum supply voltage

Transient Response and 3.3V to 2.5V or 2.5V to 1.8V Conversion

The LM39100/1/2 has excellent transient response to variations in input voltage and load current. The device

has been designed to respond quickly to load current variations and input voltage variations. Large output

capacitors are not required to obtain this performance. A standard 10µF output capacitor, preferably tantalum,

is all that is required. Larger values help to improve performance even further.

By virtue of its low-dropout voltage, this device does not saturate into dropout as readily as similar NPN-

based de-signs. When converting from 3.3V to 2.5V or 2.5V to 1.8V, the NPN based regulators are already

operating in dropout, with typical dropout requirements of 1.2V or greater. To convert down to 2.5V or 1.8V

without operating in dropout, NPN-based regulators require an input voltage of 3.7V at the very least. The

LM39100 regulator will provide excellent performance with an input as low as 3.0V or 2.5V respectively. This

gives the PNP based regulators a distinct advantage over older, NPN based linear regulators.

Minimum Load Current

The LM39100/1/2 regulator is specified between finite loads. If the output current is too small, leakage

currents dominate and the output voltage rises. A 10mA minimum load current is necessary for proper

regulation.

Adjustable Regulator Design

The LM39102 allows programming the output voltage any-where between 1.24V and the 16V maximum

operating rating of the family. Two resistors are used. Resistors can be quite large, up to 1MΩ, because of the

very high input impedance and low bias current of the sense comparator: The resistor values are calculated

by : R1=R2(Vout/1.240-1) Where Vout is the desired output voltage. Figure 1 shows component definition.

Applications with widely varying load currents may scale the resistors to draw the minimum load current

required for proper operation (see below). The current consumed by feedback resisters R1 and R2 is

calculated by: Ires = Vout / (R1+ R2).

VIN

Enable

Shutdown

LM39102

IN

OUT

EN

ADJ

GND

VOUT

R1

R2

C OUT

Figure 1. Adjustable Regulator with Resistors

Maximum Output Current Capability

The LM39100/1/2 can deliver a continuous current of 1A over the full operating junction temperature range.

However, the output current is limited by the restriction of power dissipation which differs from packages. A

Nov. 2010 - Rev. 1.5.1

- 11 -

HTC

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