Texas Instruments TPS75105DSK-529 Evaluation Board TPS75105DSKEVM-529 TPS75105DSKEVM-529 TPS75105DSKEVM-529 사용자 설명서
제품 코드
TPS75105DSKEVM-529
Setup
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JP6 – LED D2B Cathode Connection
JP6 is used to measure the current through LED D2B. Place a current meter between the pins of JP6 to
measure the current. Alternatively, a resistor may be connected between the pins of JP6 in order to
measure the current as a voltage. Place a shorting bar across the pins of JP6 if current measurement is
not required. PCB pads are provided to install a current-sense resistor across this jumper.
measure the current. Alternatively, a resistor may be connected between the pins of JP6 in order to
measure the current as a voltage. Place a shorting bar across the pins of JP6 if current measurement is
not required. PCB pads are provided to install a current-sense resistor across this jumper.
2.2
Setup
2.2.1 EVM Factory Configuration
The EVM is configured to provide the following nominal operating conditions:
Input voltage: 2.5 V to 5.5 V
LED current: 5 mA
LED current: 5 mA
2.2.2 Changing LED Current
R1 on the EVM is used to change the current. The EVM is provided with no resistor installed on R1. This
programs the default LED current of 5mA. In order to program a different LED current, place a 1% resistor
at R1 that corresponds to the following equation:
programs the default LED current of 5mA. In order to program a different LED current, place a 1% resistor
at R1 that corresponds to the following equation:
R1 = (1.22 V / ILED) × 400
Note that I
LED
is the current through each LED.
2.2.3 Using PWM Dimming
An easy dimming solution is implemented by connecting a PWM signal to ENA or ENB to dim the
respective bank of LEDs. The PWM signal may be up to 1 kHz. The scale of the LED current corresponds
directly to the duty cycle of the signal. For example, a 50% duty cycle provides 50% of the programmed
LED current. The two banks may be independently dimmed.
respective bank of LEDs. The PWM signal may be up to 1 kHz. The scale of the LED current corresponds
directly to the duty cycle of the signal. For example, a 50% duty cycle provides 50% of the programmed
LED current. The two banks may be independently dimmed.
2.2.4 Operation
1. Configure JP1 to enable or disable the bank-A LEDs as desired.
2. Configure JP2 to enable or disable the bank-B LEDs as desired.
3. Configure JP3–JP6 to measure LED current.
4. Connect the input voltage return to J2.
5. Connect the positive input voltage to J1.
6. Turn on the input voltage.
7. The LEDs that are enabled by JP1 and JP2 light.
2. Configure JP2 to enable or disable the bank-B LEDs as desired.
3. Configure JP3–JP6 to measure LED current.
4. Connect the input voltage return to J2.
5. Connect the positive input voltage to J1.
6. Turn on the input voltage.
7. The LEDs that are enabled by JP1 and JP2 light.
8
Setup
SLVU334 – August 2009
Copyright © 2009, Texas Instruments Incorporated