BT856 View Datasheet(PDF) - Unspecified

Part Name

Description

Manufacturer

BT856

YCrCb or RGB to NTSC/PAL Digital Video Encoder

Unspecified 

Bt856/7

CIRCUIT DESCRIPTION

Pin Descriptions

Pin Name

PAL

I/O

I 60

Pin #

FS ADJUST

62

VREF_IN

I 63

VREF_OUT O 64

COMP

67

R0–R7,

G0–G7,

B0–B7

VAA

GND

I 13,14, 17–20, 23,24

36–43,

28–35

– 16,22, 51,57,

61,65, 66

– 15,21,50,56

68 1,3,5,7,9

Description

NTSC/PAL mode select input (TTL compatible). A logical one config-

ures the device for PAL (B, D, G, H, I, N) operation. A logical zero con-

figures the device for NTSC operation. This pin should be connected

directly to GND if using I2C. For non-I2C use, a 10 kΩ pullup resistor (to

VAA) MUST be used to program the Bt856/7 for PAL operation. Since

this pin is also used as an analog test pin, it cannot be connected

directly to VAA or VDD.

This pin is ignored if bit D4 of subaddress register 0xDC is a logical

one. To enable PAL–M or PAL–N (Argentina), bits D1 and D0 of register

0xDA and D5 of register 0xDC (for PAL-M setup) must be set.

Full-scale adjust control pin. A resistor (RSET) connected between this

pin and GND controls the full-scale output current on the analog out-

puts. For standard operation, use the nominal RSET values shown

under Recommended Operating Conditions. The relationship between

RSET and the full-scale output current on the DAC outputs is:

RSET (Ω) = 2,055 * VREF_IN (V) / Iout FS (mA)

Voltage reference input. VREF_IN may be connected directly to

VREF_OUT. An external voltage reference can supply this input with a

1.235 V (typical) reference. A 0.1 µF ceramic capacitor must be used to

decouple this input to GND, as shown in Figures 15 and 16 in the PC

Board Layout section. The decoupling capacitor must be as close to the

device as possible to keep lead lengths to an absolute minimum.

Voltage reference output. This pin should only be used to drive the

VREF_IN pin. See Figure 16.

Compensation pin. A 0.1 µF ceramic capacitor must be used to bypass

this pin to VAA. The capacitor must be as close to the device as possi-

ble to keep lead lengths to an absolute minimum.

RGB or YCrCb (G7:B0) pixel inputs (TTL compatible). A higher index

corresponds to a greater significance.

Analog power. All VAA pins must be connected together on the same

PCB plane to prevent latchup.

Analog ground. All GND pins must be connected together on the same

PCB plane to prevent latchup.

Brooktree®

3

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