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Data Sheet

ADV7281

Rev. A | Page 19 of 32

SHORT-TO-BATTERY (STB) DIAGNOSTICS (ADV7281/ADV7281-M ONLY)

The ADV7281/ADV7281-M senses an STB event via the DIAG1

and DIAG2 pins. The DIAG1 and DIAG2 pins can sense an

STB event on either the positive or negative differential input

because of the negligible voltage drop across Resistor R1.

AIN1

AIN2

INPUT

CONNECTOR

INPUT

CONNECTOR

VIDEO INPUT

FROM SOURCE

EXT

ESD

DIAG1

1.3kΩ

100nF

1.3kΩ

100nF

430Ω

Figure 13. Diagnostic Connections

Resistors R4 and R5 divide down the voltage at the input con-

nector to protect the DIAGx pin from an STB event. The DIAGx

pin circuitry compares this voltage to a programmable reference

voltage, known as the diagnostic slice level. When the diagnostic

slice level is exceeded, an STB event has occurred.

When the DIAGx pin voltage exceeds the diagnostic slice level

voltage, a hardware interrupt is triggered and indicated by

the INTRQ pin. A readback register is also provided, which

allows the user to determine the DIAGx pin on which the STB

event occurred.

Use Equation 1 to find the trigger voltage for a selected

diagnostic slice level.

_SLICE_LEV

DIAGNOSTIC

TRIGGER

STB

(1)

where:

VSTB_TRIGGER is the minimum voltage required at the

input connector to trigger the STB interrupt on the

ADV7281/ADV7281-M.

DIAGNOSTIC_SLICE_LEVEL is the programmable reference

voltage.

PROGRAMMING THE STB DIAGNOSTIC FUNCTION

By default, the STB diagnostic function is disabled on the

ADV7281/ADV7281-M. To enable the diagnostic function,

follow the instructions in this section.

DIAG1 Pin

DIAG1_SLICER_PWRDN, User Sub Map, Address

0x5D[6]

This bit powers up or powers down the diagnostic circuitry for

the DIAG1 pin.

Table 14. DIAG1_SLICER_PWRDN Function

DIAG1_SLICER_PWRDN

Diagnostic Slice Level

Power up the diagnostic circuitry

for the DIAG1 pin.

1 (default)

Power down the diagnostic

circuitry for the DIAG1 pin.

DIAG1_SLICE_LEVEL[2:0], User Sub Map, Address

0x5D[4:2]

The DIAG1_SLICE_LEVEL[2:0] bits allow the user to set the

diagnostic slice level for the DIAG1 pin. When a voltage greater

than the diagnostic slice level is seen on the DIAG1 pin, an STB

interrupt is triggered.

In order for the diagnostic slice level to be set correctly, the

diagnostic circuitry for the DIAG1 pin must be powered up

(see Table 14).

Table 15. DIAG1_SLICE_LEVEL[2:0] Settings

DIAG1_SLICE_LEVEL[2:0]

Diagnostic Slice Level

000

75 mV

001

225 mV

010

375 mV

011 (default)

525 mV

100

675 mV

101

825 mV

110

975 mV

111

1.125 V

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