TS39302 datasheet(6/7 Pages) TSC

6 / 7 page

TS39301/2/3/4

6-7

2005/12 rev. A

Application Information (continues)

Error Flag

TS39301 versions feature an Error Flag, which looks

at the output voltage and signals an error condition

when this voltage drops 5% below its expected value.

The error flag is an open-collector output that pulls low

under fault conditions. It may sink 10mA. Low output

voltage signifies a number of possible problems,

including an over-current fault (the device is in current

limit) or low input voltage. The flag output is

inoperative

during

over

temperature

shutdown

conditions. A pull-up resistor from error flag to either

Vin or Vout is required for proper operation. For

information regarding the minimum and maximum

values of pull-up resistance, refer the graph as follow:

When the error flag is not used, it is best to leave

it open, the error flag pin can be tied directly to output

Pin.

Enable Input

TS39301/2/3/4 versions feature an active-high enable

(EN) input 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 interfacing with 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

TS39301/2/3/4 has excellent transient response to

variations in input voltage and load current.

The device have 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 47uF 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 base

designs. 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 TS39300 series 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.

Power Dissipation

Determine the power dissipation requirements for the

design along with the maximum ambient temperature at

which the device will be operated.

Pd = (Vin- Vout) * Iout + Vin * Ignd

The heat sink thermal resistance is determined by:

Өsa = [Tj(max) – Ta] / Pd – (Өjc + Өcs)

When Tj(max) < 125

oC, and Өcs is between 0 oC and 2

oC/W, the heat sink may be significantly reduced in

applications where the input voltage is known and large

compare with the dropout voltage.

Output Sense

Sense pin can be connect to the load and traces the

load voltage, TS39303/4 will adjust the output voltage to

maintain the load at expected voltage.

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