TEA5170 datasheet(6/9 Pages) STMICROELECTRONICS

Part #	TEA5170

Description	SWITCH MODE POWER SUPPLY SECONDARY CIRCUIT

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Manufacturer	STMICROELECTRONICS [STMicroelectronics]

Direct Link	http://www.st.com

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6 / 9 page

STARTING

When VCC is under 4V, output pulses are not

allowed and the slave circuit keeps its own mode.

When VCC is going over 4V, output pulses are sent

via the pulse transformer (or an optical device) to

the slave circuit which is synchronizing and enter-

ing the slaved mode. Output pulses can be shut

down only if VCC goes below 3.8 Volt.

SOFT START

Using Csf, it is possible to make a soft start se-

quence. When VCC grows from 0V to 4V, voltage

on Csf equals 0V. When VCC is higher than 4V, Csf

is loaded by a 3.7

µA current, then TonMAX (Vcsf)

will vary linearly from Tonmin to Tonmax according

to Csfst bias.

When VCC will go low (3.8 Volt threshold), Csf will

be downloaded by an internal transistor.

minimum

3.2

Duty cycle

maximum

(V)

CSF

(V)

D on max.

D on min.

Figure 6 : Soft-Start Sequence

VCC

1mA

3 Pout

1mA

from logic

Figure 7 : Electrical Schematic

POWER OUTPUT STAGE

TEA5170

6/9

TEA5170 Datasheet(PDF) 6 Page - STMicroelectronics