JAJSF01I November 2011 – March 2018 TPS65217
PRODUCTION DATA.
The TPS65217x device has a boost converter and two current sinks capable of driving two strings containing up to 10 LEDs in each string (also known as a 2 × 10 matrix) LEDs at 25 mA or one string of up to 10 LEDs at 50 mA of current. Use Equation 3 to calculate the current of each current sink.
Two different current levels can be programmed using two external RSET 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.
An internal PWM signal and I2C control support brightness and dimming. 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, or 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 1b, both current sinks are enabled, and the boost output voltage at the FB_WLED pin is regulated to support the same sink current through each current sink. The boost output voltage, however, is internally limited to 39 V.
If only one WLED string is required, short the ISINK1 and ISINK2 pins together and connect them to the cathode of the diode string. In this case, the LED current two times the sink current. Figure 22 shows the basic schematic and internal circuitry of the WLED driver used to drive two strings. Figure 23 shows the basic schematic and internal circuitry of the WLED driver used to one string. Table 33 and Table 34 list the recommended inductors and output capacitors for the WLED boost converters.