Texas Instruments TLC5940 EVM, Руководство пользователя

Страница: 7 / 19

www.ti.com
2 Board Layout
Board Layout
1.6.4 Switching Circuit for VPRG
The VPRG pin on the TLC5940 performs three functions. The TLC5940 is in grayscale mode when VPRG
= GND and in DOT correction mode when VPRG = VCC. When VPRG = 22V, the TLC5940 can program
DOT correction data into its internal nonvolatile EEPROM. The Switching Circuit for VPRG consisting of
Q1, Q2, Q3, D18, and supporting resistors is designed to switch the VPRG pins on each TLC5940
between these three voltages.
Table 6 shows the truth table for generating the VPRG voltage.
Table 6. Data Input Mode Jumper Configurations
/22V_EN VPRG_IN DCPRG VPRG Pin on TLC5940 Description
0 1 0 22 V 22V is enabled and applied to VPRG, but the data cannot be
written to the EEPROM because DCPRG is low.
0 1 1 22 V 22V is enabled and applied to VPRG. The EEPROM can now
be programmed.
1 0 1 0 V Grayscale input mode
1 1 1 3.3 V DOT correction input mode
This chapter provides the TLC5940EVM-106 board layout.
SLVU139 – September 2005 TLC5940 EVM 7