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TEF: THERMAL ERROR FLAG

LOD: LED OPEN DETECTION

OUTPUT ENABLE

SETTING MAXIMUM CHANNEL CURRENT

Imax +

V

(IREF)

R

(IREF)

31.5

(6)

TLC5945

SLVS755 – MARCH 2007

The TLC5945 provides a temperature error flag (TEF) circuit to indicate an overtemperature condition of the IC.

If the junction temperature exceeds the threshold temperature (160°C typical), TEF becomes H and XERR pin

goes to low level. When the junction temperature becomes lower than the threshold temperature, TEF becomes

L and XERR pin becomes high impedance. TEF status can also be read out from the TLC5945 status register.

The TLC5945 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

µs 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.

All OUTn channels of the TLC5945 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 operate normally. If BLANK goes low and then back high before the

grayscale counter reaches 4095, all outputs turn on for their programmed number of grayscale clocks, or the

length of time the that the BLANK signal was low, whichever 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 turn on for 200 ns.

Table 3. BLANK Signal Truth Table

BLANK

OUT0 - OUT15

LOW

Normal condition

HIGH

Disabled

31.5. The maximum output current can be calculated by Equation 6:

where:

Output currents lower than 5 mA can be achieved by setting Imax to 5 mA or higher and then using dot

correction.

connected to the IREF pin through a resistor to change the maximum output current per channel. The maximum

output current per channel is 31.5 times the current flowing out of the IREF pin.

13

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