TSM1012AID Datasheet, PDF (6/8 Pages) STMicroelectronics – LOW CONSUMPTION VOLTAGE AND CURRENT CONTROLLER FOR BATTERY CHARGERS AND ADAPTORS

TSM1012
The current-control trans-conductance operation-
al amplifier can be fully compensated. Both of its
output and negative input are directly accessible
for external compensation components.
An example of a suitable compensation network is
shown in Fig.2. It consists of a capacitor
Cic1=2.2nF and a resistor Ric1=22KΩ in series.
3. Start Up and Short Circuit Conditions
Under start-up or short-circuit conditions the
TSM1012 is not provided with a high enough sup-
ply voltage. This is due to the fact that the chip has
its power supply line in common with the power
supply line of the system.
Therefore, the current limitation can only be en-
sured by the primary PWM module, which should
be chosen accordingly.
If the primary current limitation is considered not to
be precise enough for the application, then a suffi-
cient supply for the TSM1012 has to be ensured
under any condition. It would then be necessary to
add some circuitry to supply the chip with a sepa-
rate power line. This can be achieved in numerous
ways, including an additional winding on the trans-
former.
Figure 5 :
4. Voltage clamp
The following schematic shows how to realize a
low-cost power supply for the TSM1012 (with no
additional windings).Please pay attention to the
fact that in the particular case presented here, this
low-cost power supply can reach voltages as high
as twice the voltage of the regulated line. Since
the Absolute Maximum Rating of the TSM1012
supply voltage is 28V. In the aim to protect he
TSM1012 against such how voltage values a in-
ternal zener clamp is integrated.
Rlimit = (Vcc-Vz)Ivz
Figure 4 : Clamp voltage
cc
Rlimit
Ivz
TSM1012
Vcc
Vz
28V
PWM
controller
optocoupler
primary side
Rlimit
D2
C4
47nF
C1 C2
D1
TSM1012
1
Vref
1,25V
CV+
5
R4
CC+
3
8
Vcc
28V
CV
Out
7
4
CC
CV-
optocoupler
secondary side
OUT+
R3
Rvc1 Cvc1
22K 2,2nF
R2
C3
R5
CC-
Gnd
2
6
Rsense
Ric2
1K
Ric1
22K
Cic1
2,2nF
R1
OUT-
6/8