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TSM112: Housekeeping IC.

TSM112 is a one chip solution for all PC SMPS: it

integrates on one chip the Housekeeping Circuitry

(Over Voltage and Under Voltage protections, with

adequate sequencing).

Triple Power Line Protection.

The TSM112 Housekeeping Circuit is dedicated to

3.3V, 5V and 12V power lines protection. It inte-

grates a Precision Voltage Reference, a Triple

Over Voltage Protection Circuit and a Triple Under

Voltage Protection Circuit as well as all the neces-

sary logic and transient timing management cir-

cuits for optimal and secure communication with

the motherboard, during start up, switch off and

stabilized conditions.

Over Voltage Protection

The Over Voltage Protection Circuit is made of

three comparators with internal voltage thresholds

(Vov33, Vov5, Vov12) which do not require any

external components for proper operation. The

outputs of these three comparators are ORed.

Under Voltage Protection

The Under Voltage Protection Circuit is made of

three comparators with internal voltage thresholds

(Vuv33, Vuv5, Vuv12) which do not require any

external components for proper operation. The

outputs of these three comparators are ORed, and

blanked by an internal delay circuitry (Power Up

Blanking - Tuv) which can be adjusted with an ex-

ternal capacitor (Cuv). This allows that during

power up, the under voltage protection circuit is in-

hibited.

Latch OFF

The Over Voltage and Under Voltage Circuits out-

puts are again ORed before activating a latch.

When activated, this latch commands the full

switch OFF of the three main power lines (3.3V,

5V, 12V) by an external link between the house-

keeping and the primary PWM circuits via the

main optocoupler or any other device . Note that

the Under Voltage Circuit, after Power Up UV

blanking, bears no other delay to the latch setting

input whereas the Over Voltage circuit bears an

additional Tfault delay time. This allows an effi-

cient protection against Output Short Circuit con-

ditions.

Power Good

The Over Voltage and Under Voltage Circuits are

Ored to switch the Power Good output active (PG)

to warn the motherboard that the voltage of at

least one of the three power lines is out of range.

The PG activation bears an internal Tpg delay cir-

cuitry which can be adjusted with an external ca-

pacitor (Cpg).

Remote Control

Thanks to this information link to the motherboard,

a resetting signal to the latch is achievable with

the Remote pin (REM). When the Remote pin is

active, the external Fault link between House-

keeping circuit and the PWM generator is active

(high = PWM OFF) and the PG pin is active (high).

Note that to reset effectively the latch, a minimum

width Remote pulse should be applied thanks to

an internal delay circuitry (Trem) which can be ad-

justed with an external capacitor (Crem).

TSM112

PRINCIPLE OF OPERATION AND APPLICATION HINTS