參數(shù)資料
型號: TPS65820RSHT
廠商: TEXAS INSTRUMENTS INC
元件分類: 電源管理
英文描述: 8-CHANNEL POWER SUPPLY SUPPORT CKT, PQCC56
封裝: 7 X 7 MM, GREEN, PLASTIC, QFN-56
文件頁數(shù): 74/98頁
文件大?。?/td> 2290K
代理商: TPS65820RSHT
WHITE LED CONSTANT CURRENT DRIVER
L3
3.3 H
m
SM3
PGND3
FB3
P3
OUT
GATE
DRIVE
GATE
DRIVE
500 mA
+
_
INDUCTORPEAK
CURRENT
DETECTION
LEDLOWCURRENT
DETECTION
+
_
OUTPUT OVP
DETECTION
+
_
CONTROL LOGIC AND
MINIMUMOFF TIME
MAXIMUMON TIME
SOFT
START
DUTY CYCLE
CONTROL
OFF
ON EN
ON
LEDSWITCH
FREQUENCY
ANDDUTY
CYCLE
TPS65820
250 mV
I2CREGISTER
28V
LED
SWITCH
POWER
STAGE
SWITCH
LSM3
D1
SM3_SW
R
10
FB3
W
C27
1 F
m
SLVS663B – MAY 2006 – REVISED APRIL 2008 .............................................................................................................................................................. www.ti.com
The TPS65820 has an integrated boost converter (SM3) that is optimized to drive white LEDs connected in a
series configuration. Up to six series white LEDs can be driven, with programmable current and duty cycle
adjustable via a dedicated I2C register.
The SM3 boost converter (SM3) has a 30-V, 500-mA, low-side integrated power stage switch that drives the
external inductor. Another integrated 30-V, 25-mA switch (LED switch) is used to modulate the brightness of the
external white LEDs. A simplified block diagram is shown in Figure 54
Figure 54. Simplified Block Diagram
The SM3 converter operates like a standard boost converter. The LED current is defined by the value of the
external resistor RFB3, connected from pin FB3 to AGND1. The integrated power stage switch control monitors
the LED switch current (FB3) and the integrated power stage switch current, implementing a topology that
effectively regulates the LED current independently of the input voltage and number of LEDs connected. The
high voltage rating of the integrated switches enables driving up to six white LEDs, connected in a series
configuration.
The internal LED switch, in series with the external LEDs, disconnects the LEDs from ground during shutdown. In
addition, the LED switch is driven by a PWM signal that sets the duty cycle, enabling adjustment to the average
LED current by modifying the settings of the I2C register SM3_SET. With this control method, the LED brightness
depends on the LED switch duty cycle only, and is independent of the PWM control signal.
The duty cycle control used in the SM3 converter LED switch is implemented by generating a burst of high
frequency pulses, with a pattern that is repeated periodically. For a duty cycle of 50%, all of the high frequency
pulses have a 50% duty cycle. The duty cycle control sets individual pulses to 100% duty cycle when increasing
the LED_PWM output duty cycle; for decreasing LED_PWM output duty cycles, individual pulses are set to 0%
duty cycle. An example of distinct duty cycles is shown in Figure 55, the sum of the individual pulses on/off time
over the repetition period are equivalent to the duty cycle obtained with traditional single-pulse duty cycle circuits.
76
Copyright 2006–2008, Texas Instruments Incorporated
Product Folder Link(s): TPS65820
相關PDF資料
PDF描述
TPS65820RSH 8-CHANNEL POWER SUPPLY SUPPORT CKT, PQCC56
TRU050-GACHA-47M4570000 PHASE LOCKED LOOP, CDSO16
TRU050-GACNA-12M6240000 PHASE LOCKED LOOP, CDSO16
TRU050-GALNA-20M0000000 PHASE LOCKED LOOP, CDSO16
TRU050-GALNB-51M8400000 PHASE LOCKED LOOP, CDSO16
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