TSM101AI datasheet(12/15 Pages) STMICROELECTRONICS

12 / 15 page

The current control is given by the choice of the

voltage drop through the sense resistor R5 (to be

linked to the nominal current of the application) and

by the value of the sense resistor itself.

For medium currents (< 1A), a good value for the

voltage drop through R5 can be Vsense = 200mV

(dissipation < 200mW).

The resistor bridge R2/R3 should be chosen follow-

ing equation 2 :

• Vsense = R3/(R2+R3)xVref

eq2

The total value of the resistor bridge should be in

the range of the k

Ω in order to ensure a proper

charge for the voltage reference(in the range of the

mA).

To set the current limit, the sense resistor R5 should

be chosen following equation 3 :

• Ilim = Vsense/R5

eq3

The internal current generator (Isce) can be used

to offset the current limitation with a lower value.

This current generator is activated by connecting

pin 2 to ground. It is inhibited if pin 2 is connected

to the positive rail via the pull up resistor R1.

The current offset is given by the choice of the

resistor R4.

If Ilim1 is the current limit calculated in the previous

paragraph, and Ilim2 is the current limit that is to be

set when pin 2 is connected to ground, R4 should

be chosen following equation 4 :

• R4 = (Vsense - Ilim2xR5)/Isce

eq4

where Isce = 1.4mA

C4 and C5 are bypass capacitors used to

smoothen the regulated outputs.

C2 and C3 are capacitors used for high frequency

compensation.

EXAMPLES OF COMPONENT LISTS

Table 1 summerizes a few examples of component

lists to generate quickly 15V/700mA/20 0mA,

12V/1A/500mAor 8.2V/200mA/100mAvoltage and

current regulations.

Figure 2

Table 1

Voltage /

Current

Control

15V

700mA

200mA

12V

500mA

8.2V

200mA

100mA

10k

Ω

10k

Ω

10k

Ω

1.2k

Ω

1.2k

Ω

1.2k

Ω

220

Ω

220

Ω

220

Ω

100

Ω

1.2

Ωx4

0.8

Ωx4

Ωx1

Ω

12k

Ω

8.2k

Ω

5.6k

Ω

100

Ω

100

Ω

100

Ω

2 straps

Ω

100nF

µF22µF

4.7

µF

100nF

Figure 2 represents in real dimensions thePCB and

the silkscreen of the TSM101 Evaluation board.

TSM101/A

12/15

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