Texas Instruments LP8557EVM, Руководство пользователя, Страница: 2 / 11

Changing Maximum Current on the LP8557EVM
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Table 1. Setting Boost Switching and PWM Dimming Frequencies with an External
Resistor (continued)
RFSET [ Ω ] (Tolerance) ƒ
SW
(kHz) ƒ
PWM
(kHz)
26.1k (±1%) 1000 34.2
23.2k (±1%) 1000 39.1
0 (grounded) 500 9.8
4 Changing Maximum Current on the LP8557EVM
The LP8557EVM is configured to operate at a maximum current of 20 milliamps as set by resistor R4
equal to zero ohms. This resistor can be changed to a value from Table 6 of the LP8557 datasheet which
is presented here.
Table 2. Setting Full-Scale LED Current and Boost Compensation with an External Resistor
RISET [ Ω 0 (Tolerance) Boost Compensation Option ILED (mA)
470k - 1M (±5%) 1 5
300k, 330k (±5%) 1 10
200k (±5%) 1 13
147k, 150k, 154k, 158k (±1%) 1 15
121k (±1%) 1 18
100k (±1%) 1 20
86.6k (±1%) 1 23
75.0k (±1%) 1 25
63.4k (±1%) 0 5
52.3k, 53.6k (±1%) 0 10
44.2k, 45.3k (±1%) 0 13
39.2k (±1%) 0 15
34.0k (±1%) 0 18
30.1k (±1%) 0 20
26.1k (±1%) 0 23
23.2k (±1%) 0 25
0 (grounded) 1 20
2 LP8557EVM User Guide SNVU285 – December 2013
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