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1

PRINCIPLE OF OPERATION

This technical note shows how it is possible to

calculate the current and voltage precision in the

regulation loop of the TSM1011.

The TSM1011 is a highly integrated solution for

SMPS

applications

requiring

CV

(Constant

Voltage) and CC (Constant Current) mode.

The TSM1011 integrates one voltage reference

and two operational amplifiers (with ORed outputs

- common collector).

The

voltage

reference

combined

with

one

operational amplifier makes it an ideal voltage

controller.

The other operational amplifier, combined with

few external resistors and the voltage reference,

can be used as a current limiter.

This circuit is designed for use in battery chargers

with a constant voltage and a limited output

current and in adapters.

It can be used in every type of application

requiring

0.5%

and

1%

voltage

reference

precision fixed at 2.5 Volts.

Figure 1 : Typical application using TSM1011 inSSMPS

1.1 Voltage Control

The Voltage Control loop is controlled via a first

transconductance

operational

amplifier,

the

optocoupler which is directly connected to the

output and an external resistor bridge connected

between the output positive line and the Ground

reference.

The middle point is to be connected to the CV- pin

chosen as written in Equation 1:

Equation 1

is the desired maximum output

voltage.

When under constant voltage control mode, the

bridge. To avoid the discharge of the load, the

Rsense

C2

R2

R1

C1

C3

optocoupler

secondary side

Cic1

Cvc1

Ric1

Rvc1

Rlimit

2

3

4

8

6

5

28V

Vref

Vcc

CC

CC-

CC+

Gnd

CV

CV-

CV+

Out

2,5V

R4

R5

1

R3

D1

D2

OUT+

OUT-

Ric2

TSM1011

7

PWM

controller

optocoupler

primary side

()

1

2

1

ref

lim

ref

2

1

lim

R

R

R

V

V

V

,

R

,

R

f

V

+

=

=

by Giuseppe SCUDERI

AN1623

APPLICATION NOTE

TSM1011:

REGULATION LOOPS PRECISION CALCULATION

November 2002