NCV7430

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11

Table 7. ERROR CONDITIONS FOR EACH INDIVIDUAL LED

Error Description:

ERR[2]

ERR[1]

ERR[0]

Retry Option

<RETRYSTATE>

Action:

No Error

0

0

0

No

No Action

Open circuit LEDxR

Short from ANODE to LEDxC

0

1

1

Yes

Thermal Sense

Short from LEDxC to GND (Note 12)

“Shorted LED cathode to GND”

0

1

0

Yes

ANODE OFF (Note 11)

LEDxC OFF

Open circuit (LEDxC to ANODE)

1

0

1

No

Thermal Sense

Short from ANODE to LEDxC

“Shorted LED”

1

0

0

No

Thermal Sense

Thermal Shutdown

Automatic retry below Thermal

Warning Threshold

LED & ANODE OFF

(Note 11)

11. ANODE OFF is realized by internal circuitry that switches VBIAS to 0 V. The Anode can only be switched off when an external transistor is used.

12.A short from (LEDxC) to (LEDxR), or (ANODE) to (LEDxR) may damage the device. When the external ballast transistor is not used, the

LED and/or Rsense may also be damaged.

Figure 7. Short Circuit and Open Circuit Detection

Error

Detection

Manager

GND

Short Circuit

Detection

LEDxC to GND

LED Short Circuit

Detection

LED Open Circuit

ANODE

Detection

LEDxC

LEDxR

Open Circuit

Detection

RSENSE to GND

Thermal Warning and Thermal Shutdown

The NCV7430 has thermal warning and thermal

shutdown protection features. When the junction

temperature of the NCV7430 rises above the thermal

status register. When the junction temperature rises above

<TSD> flag in the status register. <TSD> and <TW> flags

represent an event has happened and may not represent the

current state of the IC. After the <TSD> flag is set, the device

can only enter normal operation again after it is cooled down

cooling down period, the NCV7430 will resume normal

operation.

Thermal Control Bit

When the thermal control bit <TH_CONT> is set, the

NCV7430 will actively regulate the LED currents as

programmed by the user when exceeding a thermal warning

threshold. This function protects the device and the LEDs

from overheating without interaction from the LIN master.

When T<TW> is reached, the NCV7430 will decrease the

LED currents by a step defined by the parameter

TH_Ired_step. The reduction in current is represented by the

status bit <TH_CONT_STATE>. If after THtimeout

seconds the thermal warning condition is still present, the

current is decreased further. If the thermal warning

condition is removed within the THtimeout seconds, the

NCV7430 keeps the reduced current setting for the next