TSM105 ST Microelectronics, TSM105 Datasheet - Page 6

• Manufacturer Part Number: TSM105
• Description: Constant Voltage and Constant Current Controller
• Manufacturer: ST Microelectronics

TSM105
An example of a suitable compensation network is
shown in Fig.2. It consists of a capacitor
Cvc1=2.2nF and a resistor Rcv1=470K in series,
connected in parallel with another capacitor
Cvc2=22pF.
The current-control trans-conductance operation-
al amplifier has to be compensated in a different
way, since its negative input is connected to
ground. A series connection of a capacitor
Cic1=100nF and a resistor Ric1=22
between OUT and GND to stabilize the global reg-
ulation loop.
3. Start Up and Short Circuit Conditions
Under start-up or short-circuit conditions the
TSM105 is not provided with a high enough supply
voltage. This is due to the fact that the chip has its
power supply line in common with the power sup-
ply line of the system.
Therefore, the current limitation can only be en-
sured by the primary PWM module, which should
be chosen accordingly.
Figure 4 :
6/9
Rs
DS
Vcc
CS
+
+
1.210V
200mV
Ictrl
Vcc
Vsense
Rsense
+
+
-
can be put
-
TSM105
IL
Out
Vctrl
Gnd
If the primary current limitation is considered not to
be precise enough for the application, then a suffi-
cient supply for the TSM105 has to be ensured un-
der 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 numer-
ous ways, including an additional winding on the
transformer.
The following schematic shows how to realise a
low-cost power supply for the TSM105 (with no
additional windings).
Please pay attention to the fact that in the particu-
lar case presented here, this low-cost power sup-
ply can reach voltages as high as twice the volt-
age of the regulated line. Since the Absolute Max-
imum Rating of the TSM105 supply voltage is 14
V, this low-cost auxiliary power supply can only be
used in applications where the regulated line volt-
age does not exceed 7 V.
Ric1
22
Cic1
100nF
To primary
Cvc2
22pF
Rvc1
470K
D
Cvc1
2.2nF
R2
R1
+
IL
OUT+
OUT-