Dn

Sn

LEDOpen

(LOD)

VLED

FETOpen

(FOD)

FETShort

(FSD)

LEDShort

(LSD)

VADJ

Failure

Recognition

Logic

Routine

Drain

Node

Failure

Detectors

Source

Node

Failure

Detectors

XFLT

TLC5960

TLC5960

SBVS147 – SEPTEMBER 2010

www.ti.com

PROTECTION FEATURES

The TLC5960 provides protection features to keep the entire system safe. The TLC5960 internal error

recognition routine is triggered when the detection comparator detects an abnormal system status. After the error

recognition, the TLC5960 first shuts off the corresponding error channel and separates the channel from the

other normal operating channels; then, the TLC5960 indicates the error status through the XFLT buffer drive. In

cases of LED failure, the TLC5960 provides protection for both the LED open detection (LOD) and LED short

detection (LSD). Also, if the external FET fails, the FET open detection (FOD) and FET short detection (FSD)

features are provided, as shown in Figure 19.

The error status can be easily identified by monitoring the XFLT output. The XFLT output drive is designed to

toggle with a different duty ratio, each with a fixed frequency corresponding to the failure mode. The XFLT toggle

frequency is approximately 80kHz. The duty ratio is 25%, 50%, 75% ,and 100% for each of the respective failure

modes: LOD, LSD, FOD, and FSD. Table 2 summarizes the indications and the protective actions to take for all

protection modes.

The appropriate LED short detection (LSD) threshold can be selected in 4/8CH HVM mode through the HVM4

input voltage. Other detection thresholds are automatically determined internally by the TLC5960.

Figure 19. Protection Features on the TLC5960 Driver System

Table 2. Protection Feature Summary

PROTECTION

DETECTION

PROTECTIVE

RECOVERY

FUNCTION

THRESHOLD

MONITOR

LATCH

INDICATION

ACTION

CONDITION

LED open detection

Dn < 0.8V

During on

Yes

XFLT = low 25% duty

Channel off

(LOD)

LED short detection

During on

Yes

XFLT = low 50% duty

Channel off

(LSD)

high, low, high

FET open detection

Sn < VADJ/4

During on

Yes

XFLT = low 75% duty

Channel off

(FOD)

(VADJ < 1.4V)

FET short detection

Sn > 0.9V

Continuous

No

XFLT = low 100% duty

N/A

Sn < 0.7V

Thermal shutdown

VREG5 off,

Temp > +160°C

Continuous

Yes

XFLT = low 100% duty

(TSD)

all channels off

high, low, high

(1)

Detection threshold is Dn > 19.2V for HVM 2CH mode, and Dn > 8 × HVM4(V) for 4/8CH mode.

(2)

In the case of FSD, the TLC5960 has already driven Gn to a lower level so that the failed channel is shut off and no additional protection

is needed.

16

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