AN7820/24
EVALUATION BOARD
APPLICATION NOTE
FEATURES
APPLICATIONS
• 20 and 40 MSPS Conversion Rate
• On-Board Clock Drivers
• Data Output and Strobe Signal
• User Selectable Capture Clock
• On-Board Reference Drivers
• Evaluation of SPT7820 and SPT7824
• Engineering System Prototype Aid
• Incoming Inspection Tool
• Differential Linearity Error (DLE) Testing
• Integral Linearity Error (ILE) Testing
• AC Accuracy Testing: SNR, THD
• Guide for System Layout
GENERAL DESCRIPTION
The SPT7820 is capable of digitizing an analog input signal
into 10-bit words at a minimum update rate of 20 MSPS, while
the SPT7824 is capable of digitizing an analog input signal
into 10-bit words at a minimum update rate of 40 MSPS. Both
devices are pin-compatible. All input/output logic is TTLcompatible.
The EB7820/24 evaluation board demonstrates the performance of the SPT7820 and SPT7824, monolithic high speed
analog-to-digital converters (ADCs). This document can
used as an application note and as supplemental information
to the existing data sheets (SPT7820 or SPT7824). Both the
SPT7820 and SPT7824 have analog input ranges of ±2 V.
Figure 1: EB7820/24 Block Diagram. (The full detail schematic is shown in figure 17.)
+
CLK
DGND
+5
-5.2
DGND
CLK
VFT
VFB
VIN
VIN
PART OF DB792
(DAUGHTER BOARD)
LATCHES
-1
SPT7820/24
+2.5V
REF
EB7820/24
REVB
CCLK
TTL
COMP
10
Dout
10
12-BIT DAC
(80 MSPS MAX)
10
DAC
OUT
AGND
-A5.2V
+A5
- D5.2V
+D5V
ADC OUT (TTL)
The EB7820/24 (≈ 4" X 7.5") consists of five separate sections:
- Reference circuits
- Clock circuits
- SPT7820 or SPT7824, 10-bit ADC (not included with the board)
- Output latches available through 26-pin female ribbon connector
- The DB792 DAC reconstruction board is a separate daughter board (≈ 2.5" X 3.0") that directly interfaces with the
EB7820/24
POWER SUPPLIES
POWER SUPPLIES AND GROUNDING
EB7820/24 requires four power supply sources: analog 5.2 V (-A5.2 V), analog +5 V (+A5 V), digital - 5.2 V (- D5.2
V), and digital +5 V (+D5 V) . P1 is the power connector. (See
figure 2.) The recommended operating voltage range is
shown in table 1.
The SPT7820/24 requires two analog supply voltages: A5.2 V and +A5 V. The +A5 V supply is common to analog
VCC (pin 18 &25) and digital DVCC (pin 14 and 28). A ferrite
bead in series with each supply (RF1 and RF2) reduces the
transient noise injected into VCC. The bead (RF1 or RF2) to
SPT7820/24 connections should not be shared with any
other device. Bypass each power supply pin as closely as
possible to the device (0.1 µF to AGND for each VEE and
VCC pin and 0.01 µF to DGND for the DVCC pin).
Table 1 - Recommended Power Supply Operating Range
Typ
PS
Min
Typ
Max
Current
-A5.2 V -4.95 V
-5.20 V
- 5.45 V
60 mA
+A5 V +4.75 V
+5.00 V
+5.25 V
240 mA
-D5.2 V -4.95 V
-5.20 V
- 5.45 V
15 mA
+D5 V +4.75 V
+5.00 V
+5.25 V
60 mA
AGND and DGND are isolated on the SPT7820 and SPT7824.
Both -A5.2 V and +A5 V are the analog supply sources. As
in most very high speed ADCs, grounding is critical. Therefore, the ground plane technique is the most desirable for the
SPT7820/24. To accomplish this, split and tie together the
AGND and DGND ground planesonly at the device (SPT7820/
24) through an RF bead. The EB7820/24 is a four-layer
printed circuit board: the top signal, ground (AGND & DGND)
plane, power plane and the bottom signal. The two ground
planes are connected together at the device through a ferrite
bead (RF3). All three ferrite beads (RF1-3) are located close
to the ADC.
Figure 2 - P1, Power Supply Connector’s Pin Assignment
9
6
8
5
2
7
4
1
3
FEMALE
TERMINAL
The analog input (pin 21) is physically sandwiched between
the reference taps. Carefully plan printed circuit board layout
to minimize any pick-up from VIN (high frequency) into the
references (VFT or VFB).
P1 (top view)
PIN ASSIGNMENT
REFERENCE CIRCUIT
1
ANALOG - 5.2 V
2
ANALOG - 5.2 V RETURN # 1 (AGND)
3
ANALOG - 5.2 V RETURN # 2 (AGND)
4
ANALOG + 5V
5
ANALOG + 5 V RETURN (AGND)
6
DIGITAL - 5.2 V RETURN (DGND)
7
DIGITAL + 5 V
8
DIGITAL + 5 V RETURN (DGND)
9
DIGITAL - 5.2 V
The SPT7820/24 requires the use of two voltage references:
VFT and VFB. VFT is the force for the top of the voltage
reference ladder (+2.5 V typ), and VFB (-2.5 V typ) is the force
for the bottom of the voltage reference ladder. Both voltages
are applied across an internal reference ladder resistance of
900 Ω. In addition, there are three reference ladder taps:
VST, VRM and VSB. VST is the top of the reference ladder
tap (+2 V), VRM is the middle point (0.0 V typ), and VSB is the
bottom of the reference ladder tap (-2 V). The voltages seen
at VST and VSB are the expected full scale input voltages of
the device when VFT and VFB are driven to the recommended voltages (+2.5 V and -2.5 V respectively). Use VST
and VSB to monitor the actual full scale input voltages (±2 V)
by adjusting VFT and VFB. These adjustments have some
interaction; repeat a few times as needed until VST and VSB
settle at the desired voltages. Do not drive VRM as is
commonly done with a standard flash ADC converter. When
not being used (VST, VRM & VSB), decouple with a 0.01 µF
chip capacitor (surface mounted) to AGND from each tap to
minimize high frequency noise injection.
PIN#
The total power dissipation is typically 1.89 watts, including
the SPT7820 or SPT7824 (1.1 W typ).
POWER SUPPLY HOOK-UPS
Figure 3 - P1 Connector/Hook-Up
+
2
-5.2 V
3
-
+
1
4
+5V
- 5.2 V
-
+
5
6
+5V
-
+
9
7
-
8
Referring to figure 17, U2 is the + 2.5 V reference with
±150 mV of adjustable range (R1 potentiometer). U3 (OP-07) is an inverting amplifier. Its tolerance is 5% with ±300 mV
of adjustable range (R2 potentiometer). Fairchild recom-
P1 POWER CONNECTOR
AN7820/24
2
5/22/97
REFERENCE MONITORING
frequency. On both devices, the expected full scale analog
input range is from VST to VSB. The analog input is latched
at the leading edge of the CLK. There are 11 digital TTL
outputs. D0 - D9 are the parallel TTL-output bits, with D0 the
LSB, D9 the MSB and D10 the overrange bit. The data
outputs are latched at the rising edge of the CLK, with a
propagation delay of typically 14 nsec. There is one clock
latency between CLK and valid output data (see figure 5 for
more detail). The output code is a straight binary:
Table 2 - Recommended Operating Voltage Range
Table 3: SPT7820/24 Output Coding
mends that these references (VFT & VFB) be operated to
within ± 2% (or ± 2.5 V ± 50 mV) to maintain accuracy within
the specified limit. Before each EB7820/24 board is shipped,
the references are adjusted for VFT and VFB of ±2.5 V ±5 mV
respectively. For each new SPT7820 or SPT7824, VST and
VSB need to be readjusted. All measurement must be
referenced to AGND test point (provided).
Monitoring
Point
Min
VST
U1, PIN 20
+1.95 V
+2.00 V +2.05 V
R1
VSB
U1, PIN 23
- 2.05 V
- 2.00 V - 1.95 V
R2
Ref
(Ø Indicates the Flickering Bit Between Logic 0 and 1)
Typ
Max
Adjust
Analog Input
Note that the SPT7820 and SPT7824 (especially reference taps VFT VFB, VST and VRM) are sensitive to
electrostatic discharge (ESD).
0
0
0
0
1
OO OOOO OOOO
OO OOOO OOOØ
ØØ ØØØØ ØØØØ
11 1111 111Ø
11 1111 1111
Pin 21 is the analog input pin. Selecting the analog input
driver for the SPT7820/24 is less of an issue than with most
Flash ADCs because the input impedance and input capacitance are typically 300 kΩ and 5 pF, respectively. For
example, at 10 MHz and 4 VP-P sinewave input, the input
driver source only requires 0.648 mA of peak output current
(4 πFC).
Figure 4A shows one type of reference driver. Figure 4B is
another way to drive the reference circuits using force and
sense. The alternate circuit provides better control of plus
full scale (+FS) and minus full scale (-FS) errors by sensing
VST and VSB to ± 2.0 V respectively. However, the reference pins VST and VSB are not low impedance nodes that
require additional precaution when routing (PCB layout).
The analog input is directly fed from a BNC (VIN). R10 (51
Ω), analog input source termination is mounted on a socket
as a user-selectable termination. The analog input pin has
no circuit protection. Its maximum rating is from VFT to VFB
(±2.5 V). In an application in which the analog input range is
greater than ±2.5 V, protect the input pin from permanent
damage with a voltage limiter.
Figure 4A - Reference Driver
REF-03
D12 (Overrange Bit) Data Output Code
<- 2.0 V
- 2.0 V +1 LSB
0V
+ 2.0 V - 1 LSB
> + 2.0 V + 1/2 LSB
VFT
R
R
-2.5 V
+OP-07
VFB
INPUT CLOCK DRIVER
CLK is the single-ended input clock to the EB7820/24 (evaluation board), CLK IN is the input clock to the SPT7820 or
SPT7824, and CCLK is the capture clock used for the output
latches (U7 & U8).
Figure 4B - Alternative Reference Driver
OUT
+
OP-07
-
+2.5 V
+2.0 V
10 k
REF-03
0.1
10 k
10 k
+OP-07
≈ +2.5 V
VFT
+2.0 V
VST
-2.0 V
≈ -2.5 V
The clock input of the SPT7820/24 requires a TTL-logic level
of 6 nsec or faster to improve the noise. TTL-logic family
(74FXX) is good for driving the SPT7820/24. Finding a TTLsquare wave generator up to 40 MHz with fast slew rate and
low jitter is harder than a sine wave, low jitter generator. U5
(MAX9686, TTL-voltage comparator) provides most of the
above requirements to drive the SPT7820 or SPT7824 (except the low jitter generator). The CLK signal can be a sine
wave signal with the amplitude not to exceed ± 3 V (input
common mode limitation of U5). R11 (51 Ω) is the CLK
source termination. Use R3 to adjust the duty cycle of the
CLK IN. CLK IN is in phase with CLK and has a a propagation
delay of 6 nsec typically. The positive clock (CLK IN) pulse
width must be kept between 10 nsec and 300 nsec for the
VSB
VFB
SPT7820 OR SPT7824, 10-BIT ADC
The SPT7820 integrated circuit is a 10-bit analog-to-digital
converter capable of digitizing an input signal with a minimum
update rate of 20 mega-samples per second (MSPS). The
SPT7824, on the other hand is pin compatible with the
SPT7820 except that it is faster: 40 MSPS for the sampling
AN7820/24
3
5/22/97
SPT7824 and 20 to 300 nsec for SPT7820. This is due to the
internal THA. When operating the SPT7820 or SPT7824
faster than 3 MSPS, keep the clock duty cycle at approximately 50% ±10%. The probe jack PJ1 is the monitoring test
point for the CLK IN. Use this test point when adjusting the
clock duty cycle.
U7 and U8 (74F174) are the output latches. The FAST family
TTL-logic is very sensitive to electrostatic discharge (ESD).
RN1 and RN2 are the 8 pin SIP resistor networks, 10 kΩ.
They protect U7 and U8 by providing the ESD path to DGND.
The BNC connector (CCLK) is the capture clock, which has
51 Ω termination R12 on board. The outputs of the data
latches (D0-D9) are routed through the standard 26-pin
female ribbon connector (P2). SJ3-5 are the solder jumper
options for the capture clock. Only one of these jumpers
needs to be connected:
Logic low of the CLK IN (pin 17) causes the internal THA to
go into track. It is necessary to keep the SPT7820 or
SPT7824 in the track mode when the device is idle for an
extended period of time or at the start-up time. This setup will
prevent the internal THA from going to saturation due to the
internal THA’s droop. EB7820/24 provides a logic low to the
clock of the SPT7820/24 when the pulse generator (CLK) is
removed from the evaluation board.
-
When SJ3 is installed (factory installed when this board is
shipped), SPT7820/24 and the latches (U7 and U8) are
clocked at the same time. With this configuration, the data
seen at the connector P2 adds another clock of latency
(two clocks of latency total as shown in figure 6).
-
When SJ4 is installed, the capture clock must be supplied
externally through CCLK. The setup time (ts) and hold
time (th) in table 5 must be met when selecting this option.
-
When SJ5 is selected, the buffers will be latched at the
falling edge of the CLK IN (SPT7820/24). With this option,
the setup time (ts) and hold time requirements for the
74F174 latches must be met (table 5). The placement of
this capture clock edge is dependent on the clock pulse
width and the sampling frequency. This option is not
recommended above 25 MSPS to avoid latching the
invalid data.
TTL-OUTPUT DATA LATCHES
The rise time (Trise) and fall time (Tfall) of SPT7820/24 (D0D9) are not symmetrical. The propagation delay with respect
to trise (at the 2.4 V crossing) is typically 14 nsec and 6 nsec
is typical with respect to tfall (at the 2.4 V crossing). Figure
5 shows the actual output characteristic of the SPT7820/24.
This nonsymmetrical trise and tfall creates approximately
8 nsec of invalid data.
In an application where a reconstruction DAC is needed, the
above invalid data zone will cause the reconstruction signal
to have an unwanted heavy glitch if the DAC is directly
interfaced with SPT7820 or SPT7824. To avoid this, buffer
the SPT7820/24 by the edge-triggered latches. FAST family
TTL logic will fit well in this application due to its fast setup and
hold time.
Figure 5 - Digital Output Characteristic of the SPT7820 or SPT7824
N
CLK IN
N+1
2.4V
Rise Time
≤ 6nSEC
6nS
typ.
3.5V
DATA OUT
(Actual)
Invalid
Data
Invalid
Data
2.4V
(N-1)
(N-2)
(N)
0.8V
0.5V
tpd1
(14 nS typ.)
DATA OUT
(Equivalent)
(N-2)
INVALID
DATA
(N-1)
INVALID
DATA
(N-1)
The digital outputs (latched) are routed through P2, 26 pin ribbon connector. (See table 4.)
The overrange bit (D10) could be viewed through test point TP13. D10 does not bring out through P2.
AN7820/24
4
5/22/97
Figure 6 - EB7820/24 Timing Diagram Where CCLK is the Same as CLK IN
Figure 7 - EB7820/24 Timing Diagram Where CCLK is 180° Out of Phase From CLK IN
U5, pin 3
N
N+1
N+2
N+3
N+4
CLK
(EB7820/24)
tpd2
tpwH
tpwL
CLK IN
(SPT7820/24)
tpd3
VALID
(N)
ts
INVALID
tpd1
VALID
(N-1)
INVALID
VALID
(N-2)
INVALID
(SPT7820/24)
INVALID
DATA OUT
VALID
(N+1)
VALID
(N+2)
th
CCLK
(LATCHES)
tpd4
DATA OUT
(P2)
(N-2)
(N)
(N-1)
(N+1)
Table 4 - P2, SPT7820/24 Output Data (Latched) , 26-Pin Female Ribbon Connector
P2
Function
Logic
P2
Function
1
CCLK
TTL
2
DGND
3
N/A
TTL/LO
4
DGND
5
N/A
TTL/LO
6
DGND
7
D0 (LSB)
TTL
8
DGND
9
D1
TTL
10
DGND
11
D2
TTL
12
DGND
13
D3
TTL
14
DGND
15
D4
TTL
16
DGND
17
D5
TTL
18
DGND
19
D6
TTL
20
DGND
21
D7
TTL
22
DGND
23
D8
TTL
24
DGND
25
D9 (MSB)
TTL
26
DGND
Logic
DGND
DGND
DGND
DGND
DGND
DGND
DGND
DGND
DGND
DGND
DGND
DGND
DGND
AN7820/24
5
5/22/97
1) Tacq 1 is the settling time of the THA when it is in track
and it is driven by the analog input switching.
Table 5: Timing Specification
Function Description
tpd1
SPT7820/24, CLK
to Data Valid Prop
Delay
MAX9686 Prop.
Delay
SPT7820/24, T(fall)
Prop. Delay
74F174, Prop.
Delay
74F174 Setup Time
74174, Hold Time
CLK Positive Pulse
Width (SPT7820)
CLK Negative Pulse
Width (SPT7820)
CLK Positive Pulse
width (SPT7824)
CLK Negative pulse
tdp2
tdp3
tdp4
ts
th
tpwH
tpwL
tpwH
tpwL
Width (SPT7824)
Min
Typ
Max
Unit
-
14
18
nsec
-
6
9
nsec
4.5
7
10
nsec
4.5
4
4
7
-
10
-
nsec
nsec
nsec
20
-
300
nsec
20
-
-
nsec
10
-
300
nsec
10
-
-
nsec
2) Tacq 2 is the amount of time it takes for the internal
THA of the ADC to reacquire the analog input when
switching from hold to track (CLK IN from high to low)
to within 1/2 LSB.
Both Tacq 1 and Tacq 2 need the same amount of time (see
the acquisition time specification in the respective data sheet).
The low-to-high clock transition should be placed after both
the analog input and internal THA are settled. The analog
input must remain for at least 5 ns (Vin hold time) after the low
to high clock transition. Keep the clock positive pulse width
(TpwH) to within the recommended limit. (Refer to the specification in the respective data sheet.)
TIMING CONSIDERATIONS WHEN USING AN
EXTERNAL TRACK-AND-HOLD
The signal-to-noise ratio (SNR) and the total harmonic distortion (THD) degrade as the analog input frequency increases.
These parameters imply that the differential linearity error
(DLE) and the integral linearity error (ILE) degrades as well
at high frequency. This degradation is mainly due to aperture
jitter and/or analog input bandwidth limitation and/or slew rate
limitation of the SPT7820 and SPT7824. Below 1 MHz, the
SNR and THD of the SPT7820 and SPT7824 are generally
constant. In order to bring these accuracies up (at high
frequency), you may need to buffer the analog input using a
track-and-hold amplifier (THA). THAs can be imperfect (especially at high frequency); otherwise, the dynamic performance of the SPT7820 or SPT7824 would be constant and
equal to its performance at 1 MHz.
SPT7820/24 ACQUISITION TIME SPECIFICATION
Figure 8: Acquisition Time
Vin Hold time
(5 ns min)
+ 2V
ANALOG
INPUT
- 2V
Selecting an acceptable THA for a specific application is
sometimes difficult. The timing diagram shown in figure 9 and
table 6 illustrate the critical timing necessary when driving the
ADC from a THA.
TpwH
CLOCK
50%
INPUT
TRACK
INTERNAL
THA TIMING
HOLD
TRACK
Figure 9-Critical Timing Between External THA and ADC
th1
+ FS
Aperture delay
INTERNAL
Settle to 1/2 LSB
THA OUTPUT
tTHS
THA IN
- FS
Tacq 1
Tacq 2
Pedestal
tHTS
tHTS
THA OUT
The acquisition time (Tacq) is defined as the hold to track full
scale settling time for the internal track-and-hold (THA). Logic
low of the clock input corresponds to track mode and logic
high is the hold mode for the internal THA. Figure 8 shows two
types of acquisition time:
Droop
(THA tacq )
THA
DIFF CLK
TRACK
HOLD
tacq
(ADC)
ADC
CLK
tpd1
Valid Data
Invalid
Valid Data
Invalid
Invalid
ADC
OUT
AN7820/24
6
5/22/97
major concern, use AMP1 (disregard AMP2) low noise amplifier to gain up to ± 2 volts before getting to the THA. In another
application in which high frequency VIN is the major concern,
use AMP2 instead of AMP1 to amplify the THA signal to ±2
volts before reaching to SPT7820 or SPT7824. In the latter
case, the low level VIN provides a faster acquisition time for
the THA.
Table 6 : Critical Timing Specifications
Parameter
tHTS
Description
Min
THA, Hold to Track
Settling Time
X
tTHS
THA, Track to Hold
Settling Time
X
tacq
SPT7820 ADC
Acquisition Time
4 V Step
tacq
SPT7824 ADC
Acquisition Time
4 V Step
th1
Hold Time After the
ADC Rising Clock
5
X= This Limit Depends on the THA Chosen
Typ
Max Unit
X
X
X
X
UNCOMMITTED PROTO SOCKET SPACE
20
nsec
12
nsec
Referring to the detail schematic figure 17, there are two slots
available for applications where additional circuits may be
needed to interface with the EB7820/24. These two slots
(labeled A and D in the PCB assembly) are electrically
noncommitted:
nsec
The settling time to 1/2 LSB (1.953 mV) is one of the principal
requirement in a 10-bit THA. This includes both track to hold
(tTHS) and hold-to-track (tHTS) settling time. tHTS varies
with the step size (voltages) that the THA needs to swing. The
rising edge of the ADC’s clock should be placed after tTHS
has settled. SPT7820/24 requires that the analog input be
held for an additional 5 nsec minimum (th1) after the rising
edge of the clock. Figure 9 shows the ADC running at
Nyquist; the sampling frequency is practically twice the input
frequency. In this example, the ADC could have as much as
a 4 Volt step (±FS) from one conversion to the next. The
acquisition time (tacq) of the ADC must be met. This is the
time necessary to allow the internal THA of the SPT7820/24
to track (CLK= low) and settle to 1/2 LSB while the input is
sharply changed to its new continuous level. The minimum
acquisition time is 20 nsec for a 4 volt step and 12 nsec for a
0.5 volt or less step.
-
Slot A is physically located near VIN (BNC) and is intended for the analog interfacing circuit. It has one 16DIP and one 8-SIP.
-
Slot D is physically located between P2 and P3 connectors
and is intended for the digital interfacing circuit. It has
three 16-DIPs, three 8-SIPs and one 37-pin D connector.
Both slots have the appropriate power supplies and
grounds in their vicinity as labeled.
DB792 DAUGHTER BOARD (RECONSTRUCTION DAC)
DB792 (figure 18) is the daughter board that interfaces directly
to the EB7820/24 via P2 and P3. It is suited for an application
where the reconstruction DAC is needed to evaluate the ADC
performance in the time domain. DB792 is designed around
the Analog Device's AD9713, 12-bit TTL, digital-to-analog
converter, 80 MSPS update rate. It is setup in bipolar
operation. The detailed schematic is shown in figure 18.
Refer to Analog Device's AD9713B data sheet for detail.
The maximum sampling rate of the SPT7820 or SPT7824
when driving from an external THA can be decided from the
proper combination of tTHS, tHTS and tacq .
SPT7820/24 INPUT AND LATCH-UP PROTECTIONS
The SPT7820/24 is free from any possible latch-up when the
recommended interfacing circuit as shown in figure 11 is
followed. The following lists are for both latch-up and input
protection interface requirements:
The pedestal and the droop of the THA shown in figure 9 are
not critical to the dynamic performance as long as they are
constant with respect to the analog input range. They are
seen as offset errors.
SPT7820 and SPT7824 require that the analog input (VIN)
range be operated within ± 2 V ± 2%. Amplification and level
shifting are needed for a low voltage level VIN.
1) Drive the input clock (pin 15) from a TTL logic (VIH ≤ 4.5
V). Fast TTL logic family or equivalent is strongly recommended due to its fast rise time (6 nsec or faster). In the
event in which the clock is driven from a high current
source (greater than 400 mA), use a 100 Ω resistor in
series to current limit to roughly 45 mA.
Figure 10: Driving Circuit Block Diagram
2)
LOW LEVEL ANALOG INPUT SIGNAL
VIN
AMP1
THA
AMP2
D1 is a Schottkey or hot carrier diode (Motorola, 1N5817
or eq.) installed between VEE and AGND (reverse bias).
3) Both VCC (pin 18 & 25) and DVCC (pin 14 and 28) are
driven from the same analog +5 V supply.
SPT7820/24
4) Mount the ferrite beads (FB1 and FB2) as closely to the
device as possible. The bead to ADC connections should
not be shared with any other device.
Figure 10 shows the typical analog driving circuit. AMP1 and/
or AMP2 are optional. For an application in which noise is the
AN7820/24
7
5/22/97
Figure 11: Recommended Interfacing Circuit
FAST TTL
BUFFER
CLK
VIN
15
R1=100Ω
21
LIMITER
CLK
VIN
(±2V)
VST
C2
10K
30K
22
.01µF
3
1
10K
+ IC2
4
.01µF
8
.01µF
-5.2V
OP-07
+5V
2
VRM
C3
30K
23
.01µF
7
D9
10
D8
9
D7
8
D6
D5
6
5
D3
4
D2
VSB
D1
24
27
D1
26
18
C8
C10
.1µF
.1µF
C9
C11
.1µF
14
10 µF
DGND
28
2
1
13
.01µF
C6
.01µF
C7
10 µF
+
+
-5.2V
DVCC
DVCC
VCC
25
FB1
FB3
17
.1µF
3
FB2
16
VCC
C5
AGND
.01µF
VEE
+
VEE
1µF
(LSB) D0
VFB
AGND
-2.5V
7
D4
C4
6
11
VSS
20
.01µF
(MSB)
12
VCC
C1
1µF
(ORB) D10
DIGITAL OUTPUT LOGIC INTERFACE
5
Trim
GND
.01µF
+
(REF-03)
4
VFT
DGND
+
1µF
19
+2.5V
6
SPT7820/24
IC1 Vout
2 Vin
+5V
AGND
DGND
(Analog)
+5V
LOGIC
Figure 12 : An Example of an Input Limiter
5) Bypass all reference and power supply pinsas closely to
the device pin as possible (chip caps C1-11 are preferred):
0.1 µF for VCC and VEE, and 0.01µF for DVCC and Vref.
6 The top reference (VFT) driver must be current limited to
20 mA maximum if a different reference driver circuit is
used in place of the recommended circuit shown in figure 11.
VIN
LIMITER
47 Ω
To ADC
VIN
SK1
7) The limiter is required if the maximum peak-to-peak voltage of the analog input exceeds ±2.5 V. Incorporate the
limiter within the analog input driver or use the circuit
shown in figure 12. Another option is to add a 100 Ω
resistor in series to current limited the input. This last
option adds another LSB error to both ± full scale compared to only 1/2 LSB when using the circuit shown in
figure 12.
SK2
+
+2 V
-
+ -2 V
+5V
+5 V
-5.2 V
10 kΩ
10 kΩ
SK1,2 = Fast recovery Schottkey diode:
RCA, P/N SK9091 or equivalent
AN7820/24
8
5/22/97
SPT7820/24 CHARACTERIZATION
SELECTION OF THE SIGNAL GENERATORS
Performance at speed is the main goal in evaluating any
ADC, but it is beneficial to start from a relatively low speed and
verify key parameters. It is also beneficial to predict performance at speed. If the transition noise and/or the differential
linearity of the device perform poorly at low frequency, the
SNR at speed cannot be expected to be better. In addition,
the low frequency setup can be useful as a verification tool for
the test set-up.
For very high speed and high accuracy ADC testing, selection
of both analog and clock inputs is critical. Two parameters
are important in selecting the generators 1 and 2:
1) The purity of the output sinewave must be at least 76 dB
or better of SNR. An appropriate band pass filter (BPF)
installed after the generator will help improve the SNR.
2) The sampling clock jitter or aperture jitter can originate
both inside and outside the A/D converter.
At low frequency there are numerous ways of characterizing
the differential linearity error (DLE), integral linearity error
(ILE), transition noise, missing codes (MC), synchronous
noise, nonmonotonicity, power supply sensitivity and power
supply currents. Fairchild will guide the user through two
classical yet powerful testing approaches to achieve fast and
relatively accurate results.
Consider the selection of an acceptable clock generator. The
uncertainty of the clock placement due to the time jitter
(aperture jitter) degrades the effective performance of the
device. This jitter is translated into the ADC amplitude error
and is proportional to the analog input slew rate. For a
sinusoidal input, the uncertainty of the clock edge placement
from cycle to cycle due to the equipment jitter has an effect on
the A/D converter performance, especially the SNR:
High frequency or dynamic testing, the missing codes test,
ILE, DLE, VOS and the gain error tests are based on
statistical results. They can be performed using the histogram technique. SNR and THD are tested by using the fast
Fourier transform (FFT).
SNR (Max) =
Where :
and
EB7820/24 was designed to provide optimum capability in
fulfilling the above characterization needs.
Fairchild uses the following equipment when characterizing/
testing the SNR and THD: HP8644A synthesized signal
generator for both generators 1 and 2 and HP3325 function
generator for generator 3.
EQUIPMENT HOOKUP
Figure 13: Synchronous Equipment Hookup
REF
OUT
GENERATOR # 1
OUT
REF
IN
GENERATOR #2
OUT
IN
BPF
OUT
{20 LOG [1/ ( 2π Fin Tj )] + 3.02 } dB,
Fin = analog input frequency
and Tj = the aperture jitter in RMS
LOW FREQUENCY PERFORMANCE CHECK
Figure 14 : Three-Bit Reconstruction DAC
ANALOG IN
R30
CLOCK
B2
STEP
5.1 kΩ
R31
REF
IN
GENERATOR # 3
OUT
B1
CCLK (if SJ4 is installed)
10 kΩ
R32
B0 (LSB)
Coherent testing is recommended in characterizing the
SPT7820/24. All three signals (VIN, CLK and CCLK) are
synchronized. This testing gives well defined results when
using the following suggested techniques for evaluating the
performance of the device. These techniques also significantly reduce the testing time, especially the dynamic testing.
The diagram in figure 13 suggests one way to achieve this
goal. Generator 1 is the analog input. Generator 2 is the
sampling clock, sinewave and ±3 VP-P maximum. Generator 3 (only needed if solder jumper option SJ4 is used) is the
capture clock, TTL. A phase adjustment option for generator 3 is necessary to place the edge of the capture clock at the
proper setup time. R11 and R12 are 51 Ω and serve as
termination resistors for generator 2 and generator 3, respectively.
20 kΩ
R31
10 kΩ
DGND
This section describes one approach to visual evaluation of
the differential linearity error (DLE), missing codes (MC),
non-monotonicity, synchronous noise and transition noise.
The BNC DAC OUT (from the mother board, figure 18) can be
the monitoring point to view the quality of the quantization
signal, but this may pose a great deal of difficulty. Fairchild
suggests another approach commonly used in the industry.
AN7820/24
9
5/22/97
This approach is to use a three-bit reconstruction DAC
generated from LSB’s TTL outputs of the last three LSBs.
This circuit is shown in figure 17. When jumpers SJ9-SJ11
are installed, R30-R33 forms a three-bit DAC as shown in
figure 14.
to the ideal step with ±(1/n) LSB of accuracy. In this case, the
ideal step is the average of the step size. Other errors (MC,
transition noise and nonmonotonicity) can be resolved in a
similar way. Figure 15 also gives the identification of each
error from the actual transfer curve.
The output of this three bit reconstruction DAC can be
viewed through the test point STEP with the scope. For this
test, use a function generator for the generators 1 and 2
(HP3325A or equivalent) and set up for a ramp output.
Replace the BPF with an RC low pass filter (1k and 0.01 µF)
to eliminate all high frequency components. Set the slew
rate of this ramp signal to 1 LSB per n conversions (sampling period) for a desired (1/n) test resolution. A minimum
of n = 10 is recommended for this application. The P-P
voltage and the period of the ramp input are then dependent
on the selection of the number of steps (LSBs) within one
ramp’s period. You may need to remove R10 (51 Ω). Set CLK
and CCLK to the same relatively low frequency, approximately 1 MHz or even slower. Adjust as needed to meet the
tpwH and ts specifications. (See figure 5-6 and table 5.)
Example:
1) SPT7820 is operated at 500 kHz (sampling frequency).
2) (1/10) of the test resolution is desired.
3) The scope is externally triggered to the ramp input. Three
retraces of 8-level steps (or 24 total steps) per ramp’s
period are selected.
What peak-to-peak voltage (V p-p) and period (T) of the ramp
input signal are required to drive the SPT7820?
Answer:
1) Fs = 500 kHz,
2) n = 10 ,
3) m = 24, then V(p-p) = m ( FSR / 1024) = 24( 4 /1024) =
94 mV
and T = (m) ( n) / Fs = (24) (10) / 5000,000 = 480 µsec
The following formulas summarize the criteria for selecting
the analog ramp input signal:
Note that the above input signal will only cover 24 parts in
1024 of the FSR. To identify all errors through the full scale
range, slowly sweep the ramp input from -FS to +FS and
observe the output steps for the MC, transition noise, DLE
and non-monotonicity as indicated in the transfer curve
(figure 15 ). Most generators do not have the DC offset
covering the range from +2.5 V to -2.5 V. You may need to
construct an additional circuit using the classical summing
amplifier to DC offset the above ramp input signal.
The ramp peak-to-peak voltage:
Vp-p =
m(FSR/1024)
The ramp period: T = (m) ( n) / Fs Where:
m=
desired number of steps
(LSBs) per ramp’s period
Fs =
sampling frequency
FSR =
full scale range (typically
SPT7820/24's FSR is 4 V)
n=
desired test resolution or the number of conversions/LSB
The synchronous noise in an ADC is the distortion of the
performance of the device when the sampling frequency
varies. (Normally, the DLE can be clearly observed.) This is
usually caused by the digital signals being coupled back,
internally into the analog input signal. This problem is very
common for ADCs using the successive approximation register (SAR) architecture. The ADC that possesses this kind
of symptom presents some weak performances at a specific
sampling frequency (within the specified sampling rate), but
shows better results when the sampling frequency is varied
up or down from that weak spot. To verify the synchronous
noise using this set-up, slowly change the sampling frequency and observe the transfer curve, especially the changes
in DLE.
Figure 15 shows the relationship between the analog input
ramp signal and the resulting three-bit reconstruction DAC. It
shows 16 LSBs of P-P input voltage (i.e., two 8-level steps)
per period. For an ideal ADC and an ideal ramp input, its
digital output code changes state by 1 LSB every (n)th
conversion (dash line in the transfer curve). Any error in the
ADC makes the corresponding output codes change state
before or after the (n)th conversion. This error will translate
into smaller or larger respective step width. The DLE can be
judged visually by comparing the actual step size with respect
AN7820/24
10
5/22/97
Figure 15: Three-Bit Reconstruction DAC Waveform Using Analog Input Ramp
1LSB
Ramp Input
contain n conversions
Last 3-LSB codes
111
110
(B)
101
100
011
Theoretical
Actual
010
(A)
001
Missing Code
(MC)
000
Non- Monotonic DLE ≈ -1/2 LSB
LSB
(A) is the actual bit weight for the output code multiple of 011
(B) is the major transition noise. This noise level shown is greater than ± 1/2 LSB
Advantages:
Disadvantages:
1) Many tests (as stated above) can be extracted from this
one, simple test set-up.
1) The accuracy depends on human judgement and can be
very difficult if the person is not familiar with it.
2) The missing code and the transition noise can be more
accurately identified than with any other standard test
methods.
2) The exact code is not shown in the transfer curve, but in
a multiple of the last three bits of the LSB. To overcome
this problem, probe every bit using an oscilloscope or
install LEDs at each output (P3 connector) to signal the
state of each output bit.
3) Set-up is quick and relatively accurate.
AN7820/24
11
5/22/97
1.0
1.1
GENERATOR #2
BPF
OUT
GENERATOR # 3
CCLK
REF
IN
OUT
CLK
REF
IN
IN
VIN
GENERATOR # 1
EB7820/24
REF
OUT
P2
Figure 16: Dynamic Testing Test Set-up
OUT
Check for installation of jumpers SJ2B, SJ2C and SJ3.
OUT
DYNAMIC TESTING
HIGH SPEED
MEMORY
1.2
1.3
1.4
CPU / DSP
P2/P3
DB792
DAC
OUT
SCOPE OR
SPECTRUM
ANALYSER
2.0
2.1
Figure 16 is the recommended block diagram for dynamic
testing of the SPT7820 or SPT7824 using the EB7820/24
evaluation board. In earlier tests, the DAC OUT signal was
used to analyze the ADC’s dynamic performances (SNR and
THD) through a spectrum analyzer. This method of testing
presented some uncertainties. The DAC had to be near
perfect and free from glitches, and its dynamic accuracy
(DLE and ILE) had to be far better than the ADC under test.
Any errors in the DAC wereadded to the total SNR and/or
THD.
2.2
2.3
2.4
2.5
Equipment Needed
Four DC power supplies: analog +5 V, analog -5.2 V,
digital +5 V and digital -5.2 V.
One Hewlett Packard, HP3325A, function generator or
equivalent.
One DVM with 5 and 1/2 digit precision.
One Oscilloscope.
Equipment Set-Up / Hook-Up
Ensure that socket U1 does not haveSPT7820 or
SPT7824 in it.
Connect all four power supplies as shown in table 1,
and figures 2 and figure 3.
Connect the function generator to CLK BNC.
Set the CLK to 3 MHz, sine wave , ±2 V.
Connect VIN to AGND.
3.0
3.1
3.2
3.3
3.4
3.5
3.6
References Calibration
Monitor TP1 with respect to AGND test point with DVM.
Adjust R1 for +2.500 V at TP1.
Monitor TP2 with respect to AGND test point with DVM.
Adjust R2 for -2.500 V at TP2.
Turn all power to off.
Install SPT7820 or SPT7824 into U1 socket. (Fepeat
from this procedure for all new devices.)
3.7 Turn all power back to on.
3.8 Monitor U1, pin 22 (VST) with respect to AGND test
point with DVM.
3.9 Adjust R1 for +2.000 V at VST.
3.10 Monitor U1, pin 27 (VSB) with respect to AGND test
point with DVM.
3.11 Adjust R2 for -2.000 V at VSB.
3.12 Repeat the procedure from paragraph 3.8 until VST
and VSB reach the desired voltages (±2.000 V respectively).
Today, it is preferable to perform these tests by means of
digital signal processing (DSP). There are currently numerous standard software packages on the market to service
this application. The EB7820/24 provides the data outputs
through P2. (See table 5 for detail.) The reconstruction DAC
can be obtained from DB792 daughter board. Both set-ups
are very important in characterizing the dynamic performance of the SPT7820 or SPT7824.
In many cases, the speed of the capture memory is much
slower than the available output valid data of the ADC under
test. In this case, it is necessary to decimate the capture
clock at a rate of Fs/N, where N is a power of 2. The beat
frequency can be achieved by slightly changing the analog
input frequency by an amount of ∆fin. For a 4096-point FFT,
the beat frequency of ∆fin = Fc/4096 is added (or subtracted)
to the analog input frequency. 4096 data points are filled in
one test period where the input is at Fin ± (Fc/4096) and the
output is updated at 1/Fc interval. Select Fin as the multiple
(integer) of Fc to achieve a complete system synchronization. Both capture memory and the DAC run at a relatively
low update rate (Fs/N).
4.0
4.1
4.2
5.0
5.1
5.2
5.3
The daughter board, DB972, is capable of updating to 80
MSPS.
Clock Circuit Calibration
Monitor PJ1 with scope on channel 1 (externally sync
to the generator).
Observe the TTL clock and adjust R3 for approximately
50% of duty cycle.
Latches (U7 and U8) Test
Remove R10.
Connect VIN to TP1.
Monitor P2, odd number pins (7-25), with scope and
observe TTL-logic high on all pins.
Connect VIN to TP2 .
Monitor P2, odd number pins (7-25), with scope and
observe TTL logic low on all pins.
EB7820/24 CALIBRATION
5.4
5.5
This section is a guide for the DC calibration of the EB7820/
24 if needed. Note that this board was fully calibrated before
shipment. VST and VSB voltages require new calibration on
each new SPT7820 or 7824.
End of calibration Procedure
AN7820/24
12
5/22/97
EB7820/24 PARTS LIST, Rev B
#
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
Ref. Des.
C1-7,10
C20,22-28,30-32
C21,29
C50-58
D1
FB1-3
P2,3
P1
P1/Recept
PJ1-2
R3
R1,2
R10-12
R20,21
R26,27,30
R28
R32
R33
RN1,2
TP1-3,AG,DG,STEP
U1
U2
U3
U5
U7,8
N/A
N/A
N/A
N/A
N/A
N/A
N/A
EB7820/24,PCB
Description
Capacitor, Tant., 10 µF, 25V, .10"
Capacitor, 0.01 µF, Chip
Capacitor, 0.1 µF, Chip
Capacitor, 0.01 µF, 10%, Ceramic
Lead Mounted Hot Carrier Rectifier
Ferrite Bead, Lead Mounted
Ribbon Plug Connector
Power Connector, 9 Pins
Power Connector, 9 Pins, Recept
Probe Connector (25 sets/bag)
Potentiometer, 2k , 12 Turns
Potentiometer, 10k , 12 Turns
Resistor, 51 Ω, 5%, 1/8 W
Resistor, 820 Ω, 5%, 1/8 W
Resistor, 20 kΩ, 5%, 1/8 W
Resistor, 1 MΩ, 5%, 1/8 W
Resistor, 5.1 kΩ, 5%, 1/8 W
Resistor, 10 kΩ, 5%, 1/8 W
8 pin SIP Resistor, 10K, 708A Type
Test Point Terminal. 76 Mil Hole Dia
Device Under Test, 10 Bit ADC
+2.5 V Precision Voltage Reference
OP-AMP, Low Noise
Single, Fast TTL comparator, 8 DIP
HEX D Flip-Flop, TTL, Fast Series
BNC Connector, Receptacle
28-Pin DIP Socket, .600" (U1)
SIP Socket Strip, 20, Break-Away
Nylon Standoff, 1", Round
Nylon Screw, 4-40, 3/16", Round Head
Crimp Male Terminal for P3
Crimp Female Terminal for P3
Printed Circuit Board
Vendor Part Number
Sprague/199D106X0025B A1, or eq.
Sprague/11C1206X7R103J050AB, or eq.
Sprague/11C1206X7R104J050AB, or eq.
MURATA/RPE110X7R103K050V or eq.
MOT/IN5817, or eq.
Fair Rite/2743001111
T & B Ansley/622-2627, or eq.
Molex/09-18-5094, or eq.
Molex/03-09-1093, or eq
Tektronix /131-4353-00
Bourns/44F3531, or eq.
Bourns/44F3533, or eq.
Allen-Bradley/BB-510-5, or eq.
Allen-Bradley/BB-821-5, or eq.
Allen-Bradley/BB-203-5, or eq.
Allen-Bradley/BB-105-5, or eq.
Allen-Bradley/BB-512-5, or eq
Allen-Bradley/BB-103-5, or eq.
Newark stock 81F9599, or eq.
Cambion/160-2044—02-01-00, or eq.
SPT7820 or SPT7824
PMI/REF-03GP, or eq.
PMI/ OP-07EP
MAXIM/MAX9686CPA
Fairchild/74F174, or eq.
Amphenol/31-5329, or eq.
AMP/M528-611D, or eq.
Adv. Intercon./SS-020-51-TG 1, or eq.
Plastic Component Corp/C34005, or eq.
Plastic Component Corp/S120040, or eq.
Molex, 02-09-2103
Molex, 02-09-1104
Fairchild/ EB7820/24 Drawing, Rev: B
Qty
8
11
2
9
1
3
2
1
1
2
1
2
3
2
3
1
1
1
2
6
1
1
1
1
2
3
1
1
4
4
1
8
1
AN7820/24
13
5/22/97
DB792 PARTS LIST, Rev A
#
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
Ref. Des.
C1-2
C10-16
C21-25
D1
P2,3
R1
R2
R3
R4
R5
R6
R7
R8
R11,12
R20,21
R22
TP1,AG,DG
U9
U10
U11
N/A
N/A
DB792,PCB
FB1-2
Description
Capacitor, Tant., 10 µF, 25 V, .10"
Capacitor, 0.01 µF, Chip
Capacitor, 0.1 µF, 10%, Ceramic
2 Terminal IC, 1.2 V Reference
26 Pin Dual Row Vert PCB Mount Conn
Potentiometer, 10k , 12 Turns
Resistor, 7.5 kΩ, 5%, 1/8 W
Resistor, 22 Ω, 5%, 1/8 W
Resistor, 10 kΩ, 5%, 1/8 W
Resistor, 15 kΩ, 5%, 1/8 W
Resistor, 20 kΩ, 5%, 1/8 W
Resistor, 1kΩ, 5%, 1/8 W
Resistor, 1 kΩ, 5%, 1/8 W
Resistor, 150 Ω, 5%, 1/8 W
Resistor, 820 Ω, 5%, 1/8 W
Resistor, 200 Ω, 5%, 1/8 W
Test Point Terminal. 76 Mil Hole Dia
DAC/TTL, 100 MHz, 12 Bits
OP-AMP, Low Noise
OP-AMP, Low Distortion
BNC Connector, Receptacle
Crimp Male Terminal for P3
Printed Circuit Board
Ferrite Bead, Lead Mounted
Vendor Part Number
Sprague/199D106X0025B A 1, or eq.
Sprague/11C1206X7R103J050AB, or eq.
MURATA/RPE110X7R104K050V or eq.
Maxim/ ICL8069CCSQ2, or eq.
Molex 15-44-3213, or eq.
Bourns/44F3533, or eq.
Allen-Bradley/BB-752-5, or eq.
Allen-Bradley/BB-220-5, or eq.
Allen-Bradley/BB-103-5, or eq.
Allen-Bradley/BB-153-5, or eq.
Allen-Bradley/BB-203-5, or eq.
Allen-Bradley/BB-102-5, or eq.
Allen-Bradley/BB-102-5, or eq.
Allen-Bradley/BB-151-5, or eq.
Allen-Bradley/BB-821-5, or eq.
Allen-Bradley/BB-221-5, or eq.
Cambion/160-2044—02-01-00, or eq.
AD9713
PMI/ OP-07EP
AD9617JN
Amphenol/31-5329, or eq.
Molex, 02-09-2103
Fairchild/DB792,PCB Drawing, Rev: A1
Fair Rite/2743001111
Qty
2
7
5
1
2
1
1
1
1
1
1
1
1
2
2
1
3
1
1
1
1
1
1
2
AN7820/24
14
5/22/97
-A 5.2
R2
10 kΩ
+A 5
R27
20 kΩ
+5A
= B NC
= Test Point
= Prob e Jack
1
4
-5.2A
A
= Solder Jump er Op tion
C10
+
C55
6
VIN
+
C7
C6 +
PJ1
U5
D1
1
-A 5.2
+
FB3
8
4
P1
9
6
+D 5
4
+A 5
1
-A 5.2
7
POWER CONNECTOR
9
P1
6
2
5
PJ2
19
17
15
13
11
9
2
5
7
15
12
10
9
7
5
R33
Female
Terminal
STEP
R14
21
10
1
3
5
7
23
12
2
25
9
SJ9
15
3
-A 5.2
RTN
-A 5.2
RTN
- D 5.2
RTN
5
-D 5.2
(Top View)
+D 5
C58
+A 5
RTN
C4
+
-D 5.2
D GND Plane
+D 5
8
7
D V CC
6
4
C57
+D 5
RTN
4
C3
+
+D 5
FB2
D GND
TP
1
3
11
13
Figure 17 - EB7820/24 Detail Schematic, Rev B
3
C2
+
A GND
TP
FB1
D V CC
RN2
10 kΩ
6
6
14
4
7
5
3
8
11
13
10
9
14
2
C31
TP3
10 kΩ
RN1
11
12
13
D V CC
SJ5
SJ3
SJ4
14 D V CC
V EE 27
D V CC 28
2
C1
C32
3
C30
C29
U1
R12
51 Ω
AGND 26
V CC 25
A GND Plane
-A 5.2
+A 5
TP2
-2.5 V
+A 5
C27
V SB 23
C28
C25
V RM 22
V FB 24
C24
SJ2B SJ2C V IN 21
C22
V FT 19
C23
C21
C20
V CC 18
A GND 17
V EE 16
15
V ST 20
+A 5
-A 5.2
5,6
7
+2.5 V
TP1
3
+
R11
(±3 V 51 Ω
2 MA X)
-
CCLK
8
= DG ND
= AG ND
4
U3
C51
MAX9686 8
C50
2 kΩ
CLK
SPT7820/24
NOTES
7
+
2 _
3
6
R1
10 kΩ
R26
5
20 kΩ
C54
4
C5
+
C53
U2
REF-03
2
R28
1 MΩ
C56
+A 5
Analog
A
+D 5
-D 5.2
820
51Ω
-D 5.2
C52
R3
R10
820
R21
R30
R20
SJ10
+ 5D
1,16
-A 5.2 RTN
U8
74F174
-A 5.2 RTN
+A 5 RTN
SJ11
R31
15
R32
8
U7
74F174
+D 5 RTN
-D 5.2 RTN
1,16
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P2
2
4
6
8
10
12
14
16
18
20
22
24
26
D
Digital
+D 5
-D 5.2
+A 5
-A 5.2
1
3
5
7
9
11
13
15
17
19
21
23
25
P3
2
4
6
8
10
12
14
16
18
20
22
24
26
P2
28
1
2
3
4
5
6
7
8
9
26
24
22
20
18
16
14
12
10
25
23
21
19
17
15
13
11
9
7
8
6
AA
AA
AAA
AA
AAA
5
3
4
1
16
51
AD9713BAN
R12
150
150
R10
R9(TBD)
C15
3
1k
7
4
4
C22
C16
6
C21
AD9617
R8
6
7
U11
OP-07
2
+
U10
3
200
R22
+A5
-A5.2
DAC OUT
3
R11
R7
R6
20 k
2
5
200
16
-
4
14
LE
6
26
7
R5
15 k
D1
9
ICL8069CCSQ2
8
EB7820/24
C14
-A5.2
10
10 k
R4
11
10K
13
R1
-1.2V
12
EB7920/22
19
15
CIN
14
+D5
LSB
+
P3
16
D12
+A5
C2
17
TP1
-A5.2
C1
-A5.2
-A5.2
19
18
11
C13
GND
FB2
+A5
20
10
17
R3
22
18 7.5 k
24
C12
C23
.1 µF
C11
FB1
21
COUT
RS
R2
13,22
25
15
C24
.1 µF
23
22
REFIN
U9
21
12
23
C10
GND
25
24
D11
MSB
27
C24
.1 µF
26
2
1
-A5.2
+A5
2
AN7820/24
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DISCLAIMER
FAIRCHILD SEMICONDUCTOR RESERVES THE RIGHT TO MAKE CHANGES WITHOUT FURTHER NOTICE TO ANY PRODUCTS HEREIN TO
IMPROVE RELIABILITY, FUNCTION OR DESIGN. FAIRCHILD DOES NOT ASSUME ANY LIABILITY ARISING OUT OF THE APPLICATION OR USE OF
ANY PRODUCT OR CIRCUIT DESCRIBED HEREIN; NEITHER DOES IT CONVEY ANY LICENSE UNDER ITS PATENT RIGHTS, NOR THE RIGHTS OF
OTHERS.
LIFE SUPPORT POLICY
FAIRCHILD'S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS WITHOUT THE
EXPRESS WRITTEN APPROVAL OF THE PRESIDENT OF FAIRCHILD SEMICONDUCTOR CORPORATION. As used herein:
1. Life support devices or systems are devices or systems which, (a) are
intended for surgical implant into the body, or (b) support or sustain life,
and whose failure to perform, when properly used in accordance with
instructions for use provided in the labeling, can be reasonably expected
to result in a significant injury to the user.
2. A critical component is any component of a life support device or system
whose failure to perform can be reasonably expected to cause the failure
of the life support device or system, or to affect its safety or effectiveness.
www.fairchildsemi.com
© Copyright 2002 Fairchild Semiconductor Corporation
AN7820/24
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