Texas Instruments tps61040EVM-002, Руководство пользователя

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Background
1-2
1.1 Background
The TPS61040EVM uses the TPS61040 boost converter to provide 20 mA of
bias current to a four-element white LED from a single-cell Li-ion battery (3 V
to 4.2 V). The EVM operates over an input voltage range of 1.8 V to 6.0 V, but
has been optimized over a 3-V to 4.2-V input range. Operation with an input
voltage down to 1.8 V is possible, depending on the number of LEDs and the
desired bias current. The EVM can also be configured for higher or lower
output currents. For lower currents, the pin-for-pin compatible TPS61041 may
replace the TPS61040. The EVM includes two adjust pins that allow the user
to dim the LEDs using either an analog or a PWM dimming scheme. A third
dimming method available to the user is to apply a PWM signal to the enable
pin of the device. More information about output voltage and current ratings
of TPS61040/41 devices can be found in the data sheet, literature number
SLVS413.
1.2 Performance Specification Summary
Table 1−1 provides a summary of the TPS61040EVM−002 performance
specifications. All specifications are given for an ambient temperature of 25
°
C.
Although the EVM is designed for four LEDs, it may be modified to provide
power for fewer or greater than four LEDs. See the TPS61040 data sheet for
detailed specifications. The EVM may also be modified to operate at voltages
down to 1.8 V and up to 6.0 V to match the TPS61040 data sheet
specifications.
Table 1−1. Performance Specification Summary
Specification Test Conditions Min Typ Max Units
Input voltage range Iout = 20 mA 3.0 4.2 V
Load Iout = 20 mA Four white light LEDs
Output current 0.1 20 mA
Efficiency Vin = 4.2 V 86.5 %