ST AN1695 Application note
AN1695
APPLICATION NOTE
TSM108 EVALUATION BOARD 12V to 6V DC/DC CONVERTER
by Anthony BOIMOND
1 - Introduction
The TSM108 is a step down controller that features constant voltage and constant current regulation. It can drive either a P-channel Mosfet or a PNP bipolar transistor. The principle of operation of the TSM108 is widely described in the application note attached to the datasheet. The goal of this document is to describe the TSM108 Evaluation Board.
The Evaluation Board was designed to allow different converter configurations. Several options for power semiconductor footprints are available on the PCB in order to make it adaptable to a wide range of converter output power. In a first step, this application note will describe the typical application. Then the various options available on the Evaluation Board PCB will be explained.
2 - TSM108 typical application
2.1 Description
The TSM108 is especially suited for cigarette lighter accessories. The typical application described in this note is a battery charger with the following characteristics:
Input voltage: Vin = 12V
Output voltage: Vout = 6V
Maximum output current: Iout = 800mA
A picture of the Evaluation Board in the typical application configuration is shown on Figure 1. The related schematic is described on Figure 2.
Figure 1 : TSM108 Evaluation Board
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AN1695 - APPLICATION NOTE
Figure 2 : Typical application schematic
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Q4-B |
R8 |
Vin |
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Vout |
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L1 |
R17 |
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R18 |
C4 |
Q4-A |
C7 |
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R19 |
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R9 |
U1 |
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14 GD |
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200mV |
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1 VCC |
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VS |
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13 |
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ICTRL |
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12 |
C3 |
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R7 |
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ICOMP |
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9 |
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!STBY |
UV/OV/!STBY |
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R6 |
C2 |
2 |
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UV |
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VCOMP |
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8 |
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4 |
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VCTRL |
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OV |
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11 |
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5 |
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VREF |
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10 |
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2,52V |
R10 |
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C10 |
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TSM108 |
OSC |
GND |
G |
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7 |
3 |
6 |
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C1 |
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The list of components used in the typical application board is shown in the bill of material here below. All other components are not mounted. Passive components like capacitors and resistors used in this Evaluation Board are through-hole components to be more easily changed by the user. Of course, in real-life application, surface-mounted devices will be used and the whole application can fit into a very small PCB area.
Table 3 : Bill of material
Reference |
Value |
Description |
Manufacturer |
U1 |
TSM108ID |
PWM controller |
STMicroelectronics |
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Q4 |
STS3DPFS30 |
Mosfet + diode |
STMicroelectronics |
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L1 |
P0250.154T |
150µH - buck main inductor |
Pulse |
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L |
short circuit |
filtering inductor |
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C1 |
220pF |
oscillator capacitor |
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C2-C3 |
22nF |
compensation capacitors |
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C4-C7 |
47µF-25V |
buck input and output capacitors |
Rubycon ZL |
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C10 |
100nF |
voltage reference bias capacitor |
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R8-R17-R18-R19 |
1Ω |
shunt resistor |
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R6-R7 |
22kΩ-10% |
compensation resistors |
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R9 |
15kΩ-1% |
divider bridge upper resistor |
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R10 |
11kΩ-1% |
divider bridge lower resistor |
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R16-R22 |
short circuit |
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