TLC5941-Q1 Datasheet, PDF(14/27 Page) Texas Instruments – 16-CHANNEL LED DRIVER WITH DOT CORRECTION AND GRAYSCALE PWM CONTROL

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TLC5941-Q1

SLDS165 â DECEMBER 2008 ........................................................................................................................................................................................... www.ti.com

LOD: LED OPEN DETECTION

The TLC5941 has an LED-open detection circuit that detects broken or disconnected LED's. The LED open

detector pulls the XERR pin to GND when an open LED is detected. XERR and the corresponding error bit in the

Status Information Data is only active under the following open LED conditions.

1. OUTn is on and the time tpd2 (1 Âµs typical) has passed.

2. The voltage of OUTn is < 0.3V (typical)

The LOD status of each output can be also read out from the SOUT pin. See the STATUS INFORMATION

OUTPUT section for details. The LOD error bits are latched into the Status Information Data when XLAT returns

to a low after a high. Therefore, the XLAT pin must be pulsed high then low while XERR is active in order to latch

the LOD error into the Status Information Data for subsequent reading via the serial shift register.

DELAY BETWEEN OUTPUTS

The TLC5941 has graduated delay circuits between outputs. These circuits can be found in the constant current

driver block of the device (see the functional block diagram). The fixed-delay time is 20ns (typical), OUT0 has no

delay, OUT1 has 20ns delay, and OUT2 has 40-ns delay, etc. The maximum delay is 300 ns from OUT0 to

OUT15. The delay works during switch on and switch off of each output channel. These delays prevent large

inrush currents which reduces the bypass capacitors when the outputs turn on.

OUTPUT ENABLE

All OUTn channels of the TLC5941 can be switched off with one signal. When BLANK is set high, all OUTn

channels are disabled, regardless of logic operations of the device. The grayscale counter is also reset. When

BLANK is set low, all OUTn channels work under normal conditions. If BLANK goes low and then back high

again in less than 300 ns, all outputs programmed to turn on still turn on for either the programmed number of

grayscale clocks, or the length of time that the BLANK signal was low, which ever is lower. For example, if all

outputs are programmed to turn on for 1 ms, but the BLANK signal is only low for 200 ns, all outputs still turn on

for 200 ns, even though some outputs are turning on after the BLANK signal has already gone high.

Table 3. BLANK Signal Truth Table

BLANK

LOW

HIGH

OUT0 to OUT15

Normal condition

Disabled

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