ANALOG DEVICES CN-0264 Service Manual

Circuit Note

Differential SD Video Filter Amplifier with

Rev. 0

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analog, mixed-signal, and RF design challenges. For more
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Devices Connected/Referenced

ADV7391/
ADV7393

ADA4432-1

ADA4433-1

Low Power, Chip Scale 16-/8-Bit SD/HD
Video Encoder

Single-Ended SD Video Filter Amplifier
with Output Short-to-Battery Protection

Output Short-to-Battery Protection

CN-0264

A Robust Solution for Transmitting Composite Video with Output Short-to-Battery

Protection

EVALUATION AND DESIGN SUPPORT

Circuit Evaluation Boards

CN-0264 Circuit Evaluation Board (EVAL-CN0264-EB1Z)

Design and Integration Files

Schematics, Layout Files, Bill of Materials

CIRCUIT FUNCTION AND BENEFITS

The circuit in Figure 1 shows a digital-to-analog video converter
paired with a low cost, low power, fully integrated reconstruction
video filter with output short-to-batter y (STB) protection, ideal for
CVBS video transmission in harsh infotainment environments
such as automotive applications. Although many video encoders
(video DACs), such as the ADV7391, can drive a video load
directly, it is often beneficial to use a video driver at the output
of a video encoder for power savings, filtering, line driving, and
overvoltage circuit protection. The main purpose of a video
driver, typically configured as an active filter (also known as a
reconstruction filter), is twofold: it blocks the higher frequency
components (above the Nyquist frequency) that were introduced
into the video signal as part of the sampling process, and it provides
gain to drive the external

Designers of infotainment and other video systems, such as
rearview cameras and rear-seat entertainment systems, are likely
to use this circuit to transmit video for the reasons previously
stated. However, a third pressing design issue centers on the
robustness. The ADA4432-1 and ADA4433-1 provide analog
video designers with integrated ICs that offer crucial overvoltage
protection, hardened ESD tolerance, along with excellent video
specification, low power consumption, and wire diagnostic
features.

75 Ω cable to the video display.

The ADA4432-1 and ADA4433-1 are fully integrated, single-ended
and differential video reconstruction filters, respectively. They
combine overvoltage protection (STB protection) up to 18 V on
the outputs, with low power consumption and a wire diagnostic
capability. Wire diagnostics are provided by way of a logic output
that is activated when a fault condition is present. The ADA4432-1
and ADA4433-1 feature a high-order filter with a −3 dB cutoff
frequency of 10 MHz and 45 dB of rejection at 27 MHz.

The combination of STB protection and robust ESD tolerance
allows the ADA4432-1 and ADA4433-1 to provide superior
protection in the hostile environments.

The ADV7391 and ADA4432-1 are fully automotive qualified,
which makes both products ideal for infotainment and vision­based safety systems for automotive applications. The ADV7391,

ADA4432-1, and the ADA4433-1 are available in a very small

LFCSP package ideal for small footprint applications.

CIRCUIT DESCRIPTION

The ADV7391 is a low power, fully integrated digital video encoder
that converts digital 8-bit component video data from a CMOS
imager into a standard analog baseband video signal compatible
with worldwide standards. Three, 10-bit digital-to-analog video
converters (operating on V
for composite (CVBS), S-video (YC), or component (YPrPb/RGB)
analog outputs in either standard definition (SD) or high definition
(HD) video formats. The circuit in Figure 1 is configured for low
output drive through DAC1 only. To conserve more power, the
other DACs and phase-locked loop (PLL) are turned off. Low drive
mode is defined as 4.33 mA full-scale output current. The

ADV7391 contains an R

R

pin and AGND is used to control the full-scale output current.

SET

For low drive operation, R
equal 300 Ω. The resistor connected to the R
1% tolerance.

= 2.6 V to 3.46 V) provide support

AA

pin. A resistor connected between the

SET

must equal 4.12 kΩ, and RL must

SET

pin must have a

SET

engineers.

room temperature. However, you are solely responsible for testing the cir cuit and determinin g its

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CN-0264 Circuit Note

P0
P1
P2
P3
P4
P5
P6
P7

DGNDPGND

DGNDPGND

0.1µF
GND_IO

100nF
GND_IO

33µF

GND_IO

10µF

GND_IO

FERRITE BE AD

V

DD_IO

0.1µF
PGND

100nF
PGND

33µF

PGND

10µF

PGND

PV

DD

0.1µF
AGND

100nF
AGND

33µF

AGND

10µF

AGND

V

AA

0.1µF
DGND

100nF
DGND

33µF 10µF

DGND

V

DD

V

DD_IO

PV

DD

V

AA

V

DD

ADV7391/AD7393

HSYNC
VSYNC

CLKIN

AGND

AGND

DGND

DGND

GND_IO

GND_IO

R

SET

AGND

DAC 1

DAC 2

DAC 3

AGND

300Ω

COMP

2.2nF

EXT_LF

SDA
SCL

ALSB

RESET

PIXEL PORT

INPUTS

CONTROL

INPUTS/OUTPUTS

CLOCK INPUT

I

2

C PORT

DGND

V

DD

EXTERNAL LOOP

FILTER

(OPTIONAL)

1µF
AGND

4.12kΩ

75Ω

TWISTED
PAIR

PV

DD

150nF 170Ω

12nF

DGND

P8
P9
P10
P11
P12
P13
P14
P15

PIXEL PORT

INPUTS

(ADV7393 ONLY)

IN

GND

ENA

+V

S

OUT

0.1µF2.2µF

ENABLE

(INPUT)

STB

75Ω

V

AA

LFCSP PACKAGE

ADA4432-1

STB

(OUTPUT)

STB

V

AA

= 3.3V

V

DD

= 1.8V

PV

DD

= 1.8V

V

DD_IO

= 1.8V, 2.5V, OR 3.3V

LPF

10488-001

The ADV7391 includes an on-chip, PLL that allows for over­sampling video data. As shown in Figure 1, the PLL is disabled
(Subaddress 0x00, Bit 1 = 1) providing an SD oversample rate of
2×. With the PLL disabled, the external loop filter components
are removed to save space and cost.

The ADA4432-1 can be used as a pseudo differential (single-
ended) driver with an unbalanced transmission line. The pseudo
differential mode uses a single conductor to carry an unbalanced
data signal from the driver to the receiver, while a second
conductor is used as a ground reference signal.

Figure 1. Low Cost, Fully Integrated Reconstruction Filter using the ADA4432-1 (All Connections and Decoupling Not Shown)

The positive conductor connects the ADA4432-1 output to the
positive input of a differential receiver. The negative wire or ground
conductor from the source circuitry connects to the negative input
of the receiver. The output termination of the ADA4432-1 should
match the impedance of the input termination at the receiver.
For example, in a 75 Ω system, each output of the ADA4432-1 is
back terminated with 75 Ω resistors that are connected to a
resistance of 75 Ω at the receiver.

Rev. 0 | Page 2 of 5

In Figure 1, the ADA4432-1 is configured as a single-ended-to­single-ended driver that allows unbalanced transmission using
twisted pair cable, untwisted cable, or coaxial cable.