ANALOG DEVICES EVAL-AD7476, EVAL-AD7477CB Service Manual

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a

Evaluation Board for 1MSPS,

12-/ 10-Bit ADCs

EVAL-AD7476/77CB

FEATURES
Full-Featured Evaluation Board for the AD7476/

AD7477
EVAL-CONTROL BOARD Compatible
Stand Alone Capability
On-Board Analog Buffering and Reference
Various Linking Options
PC Software for Control and Data Analysis when used
with EVAL-CONTROL BOARD

INTRODUCTION

This Technical Note describes the evaluation board for
the AD7476/77. The AD7476/77 are, respectively, 12 bit
and 10 bit, high speed, low power, successive-approxima­tion ADC's. The parts operate from a single 2.35 V to

5.25 V power supply and feature throughtput rates up to
1MSPS. The parts contain a low-noise, wide bandwidth
track/hold amplifier which can handle input frequencies in
excess of 1MHz. Full data on the AD7476/77 is available
in the AD7476/77 data sheet available from Analog De­vices and should be consulted in conjunction with this
Technical Note when using the Evaluation Board.

On-board components include an AD780 which is a pin
programmable +2.5 V or +3 V ultra high precision
bandgap reference, an OP467 quad op-amp used to buffer
the analog inputs and the REF195 precision bandgap,
voltage reference, providing a 5 V reference voltage.
There are various link options which are explained in
detail on page 2.

Interfacing to this board is through a 96-way connector.
This 96-way connector is compatible with the EVAL­CONTROL BOARD which is also available from Analog

Figure 1. FUNCTIONAL BLOCK DIAGRAM

Devices. External sockets are provided for the AIN input,
the VIN input and the VBIASED input.

OPERATING THE AD7476/77 EVALUATION BOARD
Power Supplies

When using this evaluation board with the EVAL-CON­TROL BOARD all supplies are provided from the EVAL­CONTROL BOARD through the 96 way connector.

When using the board as a stand alone unit external sup­plies must be provided. This evaluation board has seven
power supply inputs: AV
DV

DD

and D

. +5 V must be connected to the AV

GND

DD

, A

, +12 V, -12 V, A

GND

GND

DD

,

input to supply the AD780 and the Ref195 voltage refer­ence. The V

for the AD7476/77 can be supplied from

DD

either the AVDD external supply or from the selected
voltage reference chip. +12 V and -12 V are used to sup­ply the OP467 quad op-amp. 0V is connected to one or
both of the A
supply a separate +5V for the 74LS04 DV
D

input must be tied to 0V. The supplies are de-

GND

inputs. The DVDD input can be used to

GND

pin. The

DD

coupled to the relevant ground plane with 10µF tantalum
and 0.1µF multilayer ceramic capacitors at the point
where they enter the board. The supply pins of the quad
op-amp and references are also decoupled to A

GND

with
10µF tantalum and a 0.1µF ceramic capacitors. The
AD7476/77 AV

supply pin is decoupled to A

DD

GND

with
10uF tantalum and 0.1µF multilayer ceramic capacitors.

Extensive ground planes are used on this board to mini­mize the effect of high frequency noise interference. There
are two ground planes, A

GND

and D

. These are con-

GND

nected at one location close to the AD7476/77.

External

Power Supplies

Vdd

Input Buffer

AD7476/77
ADC

VIN

Bias-up
Circuit

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Information furnished by Analog Devices is believed to be accurate and
reliable. However, no responsibility is assumed by Analog Devices for its
use, nor for any infringements of patents or other rights of third parties
which may result from its use. No license is granted by implication or
otherwise under any patent or patent rights of Analog Devices.

Voltage
Reference

CS

SCLK

SDATA

Power
Supply
Circuit

One Technology Way, P.O. Box 9106, Norwood. MA 02062-9106, U.S.A.
Tel: [phone] Fax: [phone]

96 Pin
DIN
Connector

EV AL-AD7476/77CB

LINK AND SWITCH OPTIONS

There are 12 link options which must be set for the required operating setup before using the evaluation board. The
functions of these options are outlined below.

Link No. Function.

LK1 This link option is used to select a 50W termination on the analog input buffer circuit.

When this link is “inserted” the 50W termination is applied.
When this link is “removed” the 50W termination is removed.

LK2 This link option controls the program pin of the AD780 voltage reference.

When this link is “inserted” the AD780 output voltage is set to +3.0 V.
When this link is “removed” the AD780 output voltage is set to +2.5 V.

LK3 This link is used to select a 50W termination on the input of the bias-up circuit.

When this link is “inserted” the 50W termination is applied.
When this link is “removed” the 50W termination is removed.

LK4 This link option is used to connect the output of either the REF195 or the AD780 to the V

AD7476/77 ( if link 12 is in position C).
When this link is in position A the AD780 supplies the V
When this link is in position B the REF195 supplies the V

voltage for the AD7476/77.

DD

voltage for the AD7476/77.

DD

LK5 This link option sets the DC bias voltage that is applied to the optional bias-up/filter circuit.

When this link is in position “A”, the bias voltage is set to the same level as the voltage that is applied
to the AD7476/77 V

pin. In this configuration a bipolar analog input applied to the Vin SMB socket is

DD

biased up by the bias circuit and is presented at the Vbiased SMB as a uni-polar signal biased around
V

/2.

DD

When this link option is placed in position “B”, the bias voltage is set to A

. In this configuration the bias-

GND

up circuit is not used.

LK6 This link option is used to select the source of the +12 V supply.

In position A, the +12 V is supplied from the EVAL-CONTROL BOARD through the 96 way connector.
In position B, the +12 V is supplied from an external source through the power connector, J6.

LK7 This link option is used to select the source of the -12 V supply.

In position A, the -12 V is supplied from the EVAL-CONTROL BOARD through the 96 way connector.
In position B, the -12 V is supplied from an external source through the power connector, J6.

LK8-9 These links control the transfer of data from the AD7476/77 during a conversion for various frequencies of

SCLK.
Link 8 and 9 should be in position "A" for slower SCLK frequencies, giving valid data on the rising edge.
Link 8 and 9 should be in position "B" for fast SCLK frequencies, giving valid data on the following edge.

LK10 This link selects the source of the Vcc +5 V supply for the 74LS04.

When this link is in position "A", Vcc power is supplied from the same power source supplying the AD7476/
77 V

pin.

DD

When this link is in position "B", V

power must be must be supplied from an external source via the power

CC

connector, J5.

LK11 This link option is used to connect the input of the VIN analog buffer to the AIN input socket or to A

When this link is in position “A” the AIN socket is tied to the input of the VIN buffer. In this configuration,
an analog signal applied to the Ain input socket is buffered and presented at the AD7476/77 VIN input.
When this link is in position “B” the VIN buffer input is tied to A

LK12 This link selects the source of the V

DD

When this link is in position “A” the V
When this link is in position “B” the V
When this link is in position “C” the V

supplied to the AD7476/77.

must be supplied from an external source via J5.

DD

is supplied from the EVAL-CONTROL BOARD.

DD

is supplied from either the AD780 or the REF195 references.

DD

GND

.

pin of the

DD

GND

.

–2–

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EV AL-AD7476/77CB

SET-UP CONDITIONS

Care should be taken before applying power and signals to the evaluation board to ensure that all link positions are
as per the required operating mode. Table I shows the position in which all the links are set when the evaluation
board is sent out.

Table I. Initial Link and Switch Positions

Link No. Position Function.
LK1 Removed 50W termination resistor is not applied to the input of the VIN circuit.

LK2 Removed AD780 is set to provide a +2.5V reference.

LK3 Removed 50W termination resistor is not applied to the input of the bias-up circuit.

LK4 Removed This is not relevant due to the position of LK12.

LK5 A EVAL-CONTROL BOARD is selected as the DC bias voltage for the optional

bias-up/filter circuit.

LK6 A +12V supplied from EVAL-CONTROL BOARD via J4.
LK7 A -12V supplied from EVAL-CONTROL BOARD via J4.

LK8 B SCLK signal from EVAL-CONTROL BOARD is not inverted, (for faster values

of SCLK).

LK9 B SCLK signal from EVAL-CONTROL BOARD is not inverted, (for faster values

of SCLK).

LK10 Removed This is not relevant due to the position of LK8 and LK9, (As 74LS04 is not in

use).

LK11 A Ain SMB is connected to the input of the analog input buffer.

LK12 B VDD for the AD7476/77 is supplied from the EVAL-CONTROL BOARD via J4.

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–3–

EV AL-AD7476/77CB

EVALUATION BOARD INTERFACING

Interfacing to the evaluation board is via a 96-way connec­tor, J4. J4 is used to connect the evaluation board to the
EVAL-CONTROL BOARD or other system. The pinout
for the J4 connector is shown in Figure 2 and its pin des­ignations are given in Table II.

1

A
B
C

1

32

32

Figure 2. Pin Configuration for the 96-Way
Connector, J1

96-Way Connector Pin Description

D R0 Data Receive Zero. This input is connected to the

SDATA pin of the AD7476/77.

TFS0/RFS0 Transmit/Receive Frame Sync Zero. These two

outputs are connected to the CS pin of the
AD7476/77.

SCLK0 Serial Clock Zero. This serial clock is connected

to the SCLK pin of the AD7476/77 with the
option of an inverting buffer.

DGND Digital Ground. These lines are connected to

the digital ground plane on the evaluation
board. It allows the user to provide the digital
supply via the connector along with the other
digital signals.

AGND Analog Ground. These lines are connected to

the analog ground plane on the evaluation board.

AV

DD

Analog +5 V Supply. These lines are connected

to the AV

supply line on the board.

DD

+12V +12 V Supply. This line is connected to the +12

V supply line on the board via LK6.

-12V -12 V Supply. This line is connected to the -12
V supply line on the board via LK7.

Table II. 96-Way Connector Pin Functions.

Row A RowB RowC

1
2
3
4 DGND DGND DGND
5 DR0
6 TFS0 RFS0
7 SCLK0 SCLK0
8
9
10
11
12 DGND DGND DGND
13
14
15
16 DGND DGND DGND
17
18
19
20 DGND DGND DGND
21 AGND AGND AGND
22 AGND AGND AGND
23 AGND AGND AGND
24 AGND AGND AGND
25 AGND AGND AGND
26 AGND AGND AGND
27 AGND
28 AGND
29 AGND AGND AGND
30 -12 V AGND +12 V
31
32 AVDD AVDD AVDD

–4–

Note : The unused pins of the 96-way connector are not shown.

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