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Power-Up Characteristics

t - Time = 10 ms/div

V

(5 V/div)

O

V (2 V/div)

I

I (2 A/div)

I

Overtemperature Protection

PTN04050C

SLTS251 – SEPTEMBER 2005

Table 3. Recommended Input/Output Capacitors (continued)

CAPACITOR CHARACTERISTICS

QUANTITY

85

°C

CAPACITOR VENDOR/

EQUIVALENT

VENDOR

WORKING

MAXIMUM

PHYSICAL

COMPONENT

VALUE

SERIES

INPUT

OUTPUT

NUMBER

VOLTAGE

RIPPLE

SIZE

SERIES

(

µF)

RESISTANCE

BUS

BUS

(V)

CURRENT

(mm)

(ESR) (

Ω)

Murata X7R Ceramic

25

22

0.002

>1000

3225

5

≤5

GRM32ER61C226K

C1210C226K3PAC

Kemet X7R Ceramic

16

22

0.002

>1000

3225

5

When configured per the standard application, the PTN04050C power module produces a regulated output

voltage following the application of a valid input source voltage. During power up, internal soft-start circuitry slows

the rate that the output voltage rises, thereby limiting the amount of in-rush current drawn from the input

source.Figure 15 shows the power-up waveforms for a PTN04050C, operating from a 5-V input and with the

output voltage adjusted to 12 V. The waveforms were measured with a 1-A resistive load.

Figure 15. Power-Up Waveforms

A thermal shutdown mechanism protects the module's internal circuitry against excessively high temperatures. A

rise in temperature may be the result of a drop in airflow, a high ambient temperature, or a sustained overcurrent

condition. If the junction temperature of the internal control IC rises excessively, the module turns its boost

module restarts boost operation when the sensed temperature decreases by approximately 10 degrees.

Note: Overtemperature protection is a last resort mechanism to prevent damage to the module. It should not be

relied on as permanent protection against thermal stress. Always operate the module within its temperature

derated limits, for the worst-case operating conditions of output current, ambient temperature, and airflow.

Operating the module above these limits, albeit below the thermal shutdown temperature, reduces the long-term

reliability of the module.

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