Datasheet

SYS
4.7mF
L4
FB_WLED
ISINK1
ISINK2
BOOST
CONTROL
ISET1
ISET2
R2R1
1
0
ISEL
PWM
generator
FDIM[1:0]
DUTY[6:0]
SYS
4.7mF
L4
FB_WLED
ISINK1
ISINK2
BOOST
CONTROL
ISET1
ISET2
2xR22xR1
1
0
ISEL
PWM
generator
FDIM[1:0]
DUTY[6:0]
SET
LED
R
V
I
24.1
1048´=
TPS65217A, TPS65217B, TPS65217C, TPS65217D
www.ti.com SLVSB64F –NOVEMBER 2011–REVISED APRIL 2013
WHITE LED DRIVER
TPS65217 contains a boost converter and two current sinks capable of driving up to 2 x 10 LEDs at 25 mA or a
single string at 50 mA of current. The current per current sink is approximated by the following equation:
(7)
Two different current levels can be programmed using two external R
SET
resistors. Only one current setting is
active at any given time and both current sinks are always regulated to the same current. The active current
setting is selected through the ISEL bit of the WLEDCTRL1 register.
Brightness dimming is supported by an internal PWM signal and I
2
C control. Both current sources are controlled
together and cannot operate independently. By default, the PWM frequency is set to 200 Hz, but can be changed
to 100 Hz, 500 Hz, and 1000 Hz. The PWM duty cycle can be adjusted from 1% (default) to 100% in 1% steps
through the WLEDCTRL2 register.
When the ISINK_EN bit of WLEDCTRL1 register is set to 1, both current sinks are enabled and the boost output
voltage at the FB_WLED pin is regulated to support the same I
SINK
current through each current sink. The boost
output voltage, however, is internally limited to 39 V.
If only a single WLED string is required, short ISINK1 and ISINK2 pins together and connect them to the Cathode
of the diode string. Note that the LED current in this case is 2 x I
SINK
.
Figure 17. Block Diagram of WLED Driver. LEFT: Dual string operation. RIGHT: Single string operation
(same LED current as dual string). Note that for single string operation both ISINK pins are shorted
together and RSET values are doubled.
Table 3. Recommended Inductors for WLED Boost Converter
DIMENSIONS
PART NUMBER SUPPLIER VALUE (µH) R
DS
(mΩ) MAX RATED CURRENT (A)
(mm x mm x mm)
CDRH74NP-180M Sumida 18 73 1.31 7.5 x 7.5 x 4.5
P1167.183 Pulse 18 37 1.5 7.5 x 7.5 x 4.5
Table 4. Recommended Output Capacitors for WLED Boost Converter
VOLTAGE RATING
PART NUMBER SUPPLIER VALUE (µF) DIMENSIONS DIELECTRIC
(V)
UMK316BJ475ML-T Taiyo Yuden 50 4.7 1206 X5R
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