PT6935 datasheet(2/12 Pages) TI

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PT6935 Series

11-A 5V/3.3V-Input Dual Output

Integrated Switching Regulator

Power-up Sequencing and Vo1/Vo2 Loading

Power-up Sequencing

The PT6935 series of regulators provide two output voltages,

Vo1 and Vo2. Each of the output voltage combinations

offered by the PT6935 series provides power for both a low-

voltage processor core, and the associated digital support

circuitry. In addition, each output is internally sequenced

during power-up and power-down to comply with the

requirements of most DSP and µP IC’s, and their accompa-

nying chipsets. Figure 1 shows the typical waveforms of the

output voltages, Vo1 and Vo2, from the instance that either

input power is applied or the module is enabled via the

Standby pin. Following a delay of about 10 to 15 milli-secs,

the voltages at Vo1 and Vo2 rise together until Vo2 reaches

its set-point. Then Vo1 continues to rise until both output

voltages have reached full voltage.

Vo1/Vo2 Loading

The output voltages from the PT6935 series regulators are

independently regulated. The voltage at Vo1 is produced

by a highly efficient switching regulator. The lower output

voltage, Vo2, is derived from Vo1. The regulation method

used for Vo2 also provides control of this output voltage

during power-down. Vo2 will sink current if the voltage at

Vo1 attempts to fall below it.

The load specifications for each model of the PT6935

series gives both a ‘Typical’ (Typ) and ‘Maximum’ (Max)

load current for each output. For operation within the

product’s rating, the load currents at Vo1 and Vo2 must

comply with the following limits:-

•Io2 must be less than Io2(max).

• The sum-total current from both outputs (Io1 + Io2)

must not exceed Io1(max).

In the case that either Vo1 or Vo2 are adjusted to some

other value than the default output voltage, the absolute

maximum load current for Io2 must be revised to comply

with the following equation.

Io2 (max)

2.5

Adc

Vo1 – Vo2

Consult the specification table for each model of the series

for the actual numeric values.

Figure 1; PT6935 Series Power-up

V1 (1V/Div)

V2 (1V/Div)

Vstby

(10V/Div)

HORIZ SCALE: 5ms/Div

General Specifications (Unless otherwise stated, Ta =25°C, Vin =5V)

PT6935 Series

Characteristic

Symbol

Conditions

Min

Typ

Max

Units

Short Circuit Current

Isc

Io1 + Io2 combined

—

Switching Frequency

ƒo

Over Vin range

300

350

400

kHz

Standby (Pin 3)

Referenced to GND (pin 7)

Input High Voltage

VIH

—

Open (1)

Input Low Voltage

VIL

–0.1

—

+0.4

Input Low Current

IIL

—

-0.5

–

Standby Input Current

Iin standby

pin 3 to GND

—

External Output Capacitance

330 (2)

—

3,300 (2)

µF

—

330

MaximumOperating

Over Vin Range

–40 (3)

—

+85 (4)

°C

TemperatureRange

Storage Temperature

—

–40

—

+125

°C

Mechanical Shock

Per Mil-STD-883D, Method 2002.3

1msec,½Sine,mounted

—

500

—

G’s

Mechanical Vibration

Per Mil-STD-883D, Method 2007.2

—

15 (5)

—G’s

20-2000 Hz, Soldered in a PC board

Weight

—

Vertical/Horizontal

—

grams

Flammability

—

MeetsUL94V-O

Notes:

(1) The Standby (pin 3) has an internal pull-up, and if it is left open circuit the module will operate when input power is applied. The open-circuit voltage is less

than 15V. Refer to the application notes for interface considerations.

(2) A value of 300µF is sufficient if Oscon® or low ESR tantalum type capacitors are used. The total combined ESR of all output capacitance at 100kHz must

be (greater than) >12 m

Ω, and (less or equal to) ≤150mΩ.

(3) For operating temperatures below 0°C, Cin and Cout must have stable characteristics. Use either tantalum or Oscon® capacitors.

(4) See Safe Operating Area curves for the specific output voltage combination, or contact the factory for the appropriate derating.

(5) Only the case pins on through-hole pin configurations (N & A) must be soldered. For more information see the applicable package outline drawing.

Input/Output Capacitors: The PT6935 series requires a 330µF electrolytic capacitor at both the input and output for proper operation (300µF for Oscon® or low ESR

tantalum). In addition, the input capacitance must be rated for a minimum of 1.0Arms ripple current. For transient or dynamic load applications, additional capacitance

may be required. Refer to the application notes for more information.

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