TSM111

13/17

EVALUATION BOARD - TECHNICAL NOTE

TSM111 is a Housekeeping IC which is best used

in PC Switch Mode Power Supplies for secondary

3.3V, 5V, and 12V power lines protection.

TSM111 integrates all the necessary functions for

a secure and reliable overcurrent and overvoltage

protection, as well as a logic interface for proper

communication with the motherboard and adjust-

able timing circuitry for optimized sequencing

management. Moreover, TSM111 integrates two

precise shunt voltage references for direct opto-

coupler drive. TSM111, integrating the equivalent

of more than 25 discrete components, saves a lot

of design time and fine tuning, as well as PCB ar-

ea, and increases the reliability of the whole appli-

cation.

How to use the TSM111 Evaluation Board ?

This evaluation board allows to adapt the TSM111

housekeeping chip to an already existing PC Pow-

er Supply by simply choosing proper values for it’s

external components, and making the adequate

connections to the I/O of the evaluation board.

The Electrical Schematic of the TSM111 evalua-

tion board is shown on figure 1. It includes the

TSM111 as well as the minimum component num-

ber required to make the TSM111 fit in a PC

SMPS application.

Components calculations

The overvoltage protection is not to be adjusted.

Internal voltage thresholds are given by Vvs1,

Vvs2, Vvs3 for respective protection of the 3.3V,

5V, 12V power lines.

The overcurrent protection is given by the choice

of the Sense resistors R1, R2, R3 (respectively for

each power line 3.3V, 5V, 12V). Internal precise

voltage thresholds define the tripping voltage

drops for each line following equations 1, 2 & 3 :

Vcs1 = R1 x I33

eq1

Vcs2 = R2 x I5

eq2

Vcs3 = R3 x I12

eq3

where I33, I5, and I12 are the tripping currents.

The system will latch (Fault output will be active -

high) if the overcurrent lasts more than the autho-

rized surge delay Tsur given by equations 4 & 5 :

Icharge = Vcc / R4

eq4

Tsur = (C1 x Vsur) / Icharge

eq5

Note that eq4 is an approximation of a capacitive

charge where Vcc (16V min) is large versus the

threshold voltage Vsur (2.5V).

R4=33k

Ω, C1=4.7µF => Tsur=21ms

Thanks to the Tsur adjustment, the normal surge

currents which occur during power up (capacitive

oads charging) are blanked for a time depending

on each application.

PG

9

Tpor

10

Rem

7

UV

11

Tsur

17

PWM

6

U1

TSM111

R1

rs3.3V

R2

rs5V

R3

rs12V

D1

UV

R4

Rsur

C1

Csur

C2

Crem

R5 R rem

C3

Cpor

R6

1

2

J1

Vdet

1

2

J2

Fault

1

2

J3

Optaux

1

J5

In3.3V

1

J6

1

J7

In3.3V

Vdet

Optaux

Fault

In5V

In12V

Out12V

Out5V

Out3.3V

1

J8

Out12V

1

J9

Out5V

1

J10

Out3.3V

PG

1

2

J11

PG

1

2

3

4

SW1

BP Rem

1

2

J12

Rem

From µc

5Vstby

5Vstby

1

2

J13

Vcc

1

2

J14

Gnd

VCC

1

2

J15

VrefMain

VrefMain

R7

RoptMain

VrefAux

R8

R9

Roptaux

C4

C5

1

2

J16

VrefAux

R10

1

2

J20

D5

D6

I

1INV

1

2

J18

OptMain

OptMain

Vin

2

Vout

3

U2 78L05

5Vstby

+

C7

R11

5Vstby

In5V

IN12V

EVALUATION BOARD - ELECTRICAL SCHEMATIC

C6