UM0422 STMICROELECTRONICS | Alldatasheet
Document overview
- Manufacturer or author: Provided By ALLDATASHEET.COM(FREE DATASHEET DOWNLOAD SITE)
- PDF pages: 14
Technical content
Datasheet sections
- 1 Background
- 2 Detailed description
- 3 Pin functions
- 4 Description of the board
- 4.1 Input/output connections
- 4.2 Setup
- 5 Schematic and bill of materials
- 5.1 Schematic
- 5.2 Bill of materials (BOM)
- 6 Board layout
- 7 Application information
- 7.1 Thermal information
- 8 Revision history
glass, and low voltage DC operated. evaluation board. It includes a schematic diagram, bill of materials (BOM), and test data. Figure 1. STCS1A evaluation board Table 1. Device summary
1 Background
efficiency, size, and cost of the complete solution. LEDs are current-driven devices whose brightness is proportional to their forward current. adequate current control or the system efficiency necessary for high current LEDs. Figure 2. Constant voltage control the voltage across a current-sense resistor rather than regulating the output voltage.
Figure 3. STCS1A application diagram for 0.5 A LED current
2 Detailed description
of the slope of the edges of the LED current during the PWM dimming mode. capacitors. An open drain pin output provides information on load disconnection. A more detailed description of STCS1 device can be found in the STCS1 datasheet.
3 Pin functions
4 Description of the board
is the maximum voltage between drain and GND with a current on ILEDs equal to 1.5 A. Table 2. Pin function 1 VCC Supply voltage. Must be closely decoupled to ground . the device is completely off and the current consumption is less than 1 µA. 4 DRAIN Internal power N-MOSFET drain. with an external sensing resistor connected between this pin and GND. CSLOPE with a constant current. part has the same behavior of STCS1. system to alert that a problem occurs in the LEDs. internally connected to ground.
signal between 0% to 100% using the R9 trimmer. connector and keeping the J3 connector floating.
4.1 Input/output connections
Table 3 describes the input/output connections. Table 3. Input/output connections – Connecting the LEDs chain between A and K pins. CC and A pins shorted to supply LEDs branch. Use this connector to enable and disable the controller. – EN and the 5 V pins shorted to enable the controller. – EN and the GND pins shorted to disable the controller. – If EN pin is left open, the EVM does not operate correctly.
4.2 Setup
- Connect a power supply source between the V CC and GND pin of J1. The EVM
STCS1 absolute maximum input voltage rating of 45 V.
- Connect the LEDs between the LED anode (J1 - A) and LED cathode (J1 - K)
CC and A pins of J1 connector with a jumper to supply the LEDs branch.
- Continuous current mode: PWM = 5 V
- Dimming mode with the PWM signal of the oscillator implemented on evaluation board.
d) R9: It is possible to change the duty cycle of the PWM signal from zero to 100%.
- Dimming mode with external PWM signal.
– J4: PWM and 5 V pins shorted. PWM dimming mode with oscillator implemented on board. signal generated by the oscillator on the board. – J4: External PWM signal between PWM and GND pins. Table 3. Input/output connections (continued)
5 Schematic and bill of materials
5.1 Schematic
Figure 4. Schematic - power section highlighted blue box in Figure 4). Figure 5. Schematic - PWM oscillator
5.2 Bill of materials (BOM)
Table 4. Bill of materials
1 C1 22 nF ± 10%, X7R, 16 V GRM188R71C223KA01 Murata 0603
1 C3 1 µF± 10%, X7R, 50 V GRM21BR71H105KA12 Murata 0805
4 CSLOPE2,
1 D1 Disc LED LH R974
1 D3 White LED LXHLPW09 B Lumileds
1 D4 Schottky diode BAT46ZFILM STMicroelectronics SOD-123
2 J2,J4 CON3
1 J5 JUMPER
3 R4,R7 10 k Ω, 1%, 1/16 W 0805
1 Rf 100 Ω, 1%, 1/16 W 0805
2 R2,R1 18 k Ω ± 1%, 1/4 W 0805
1 R6 330 ± 1%, 1/4 W 0805
1 R10 220 k Ω ± 1%,1/4 W 0805
1 R13 180 ± 1%, 1/4 W 0805
1 U1 Current control STCS1APUR STMicroelectronics QFN 3X3-8L
1 U3 Voltage regulator L78L05ABUTR STMicroelectronics SOT89
6 Board layout
- The sense resistor must be placed as close as possible to feedback and ground pins. The traces should be as short as possible.
- STCS1 exposed pad area should be as large as possible to improve power dissipation. If a 2-layer PCB is used, one layer should be assigned as ground layer and a good connectivity between both layers should be observed. Figure 6, Figure 7 and Figure 8 show the board layout for the STCS1 constant current control evaluation board.
Figure 6. Assembly layer Figure 7. Top layer
Figure 8. Bottom layer
7 Application information
7.1 Thermal information
conductivity enabling high power application. Table 5. Thermal data
- This value is referred to four-l ayer PCB, JEDEC standard test board.
- With two sides, two planes PCB fo llowing EIA/JEDEC JESD51-7 standard.
8 Revision history
Figure 9. Maximum power dissipation vs T A Figure 10. Maximum power dissipation vs T A Table 6. Document revision history