AD8436BRQZ-RL [ADI]
Low Cost, Low Power, True RMS-to-DC Converter;
| 型号： | AD8436BRQZ-RL |
| 厂家： | 
ADI |
| 描述： | Low Cost, Low Power, True RMS-to-DC Converter |
| 文件： | 总21页 (文件大小：762K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
Low Cost, Low Power,
True RMS-to-DC Converter
AD8436
Data Sheet
FEATURES
FUNCTIONAL BLOCK DIAGRAM
CAVG CCF
Delivers true rms or average rectified value of ac waveform
Fast settling at all input levels
Accuracy: 10 μV 0.25% of reading (B grade)
Wide dynamic input range
100 μV rms to 3 V rms (8.5 V p-p) full-scale input range
Larger inputs with external scaling
Wide bandwidth:
VCC
AD8436
100kΩ
SUM
IGND
100kΩ
8kΩ
RMS CORE
10pF
RMS
VEE
OGND
OUT
16kΩ
1 MHz for −3 dB (300 mV)
65 kHz for additional 1% error
10kΩ
10kΩ
Zero converter dc output offset
No residual switching products
Specified at 300 mV rms input
IBUFGN
IBUFIN–
IBUFIN+
–
IBUFOUT
FET OP AMP
Accurate conversion with crest factors up to 10
Low power: 300 µA typical at 2.4 V
High-Z FET separately powered input buffer
+
OBUFIN+
OBUFIN–
+
–
DC BUFFER
OBUFOUT
R
IN ≥ 1012 Ω, CIN ≤ 2 pF
16kΩ
Precision dc output buffer
Wide power supply voltage range
Dual: 2.4 V to 18 V; single: 4.8 V to 36 V
4 mm × 4 mm LFCSP and 8 mm × 6 mm QSOP packages
ESD protected
Figure 1.
GENERAL DESCRIPTION
The AD8436 is a new generation, translinear precision, low
power, true rms-to-dc converter loaded with options. It computes a
precise dc equivalent of the rms value of ac waveforms, including
complex patterns such as those generated by switch mode power
supplies and triacs. Its accuracy spans a wide range of input levels
(see Figure 2) and temperatures. The ensured accuracy of ≤ 0.5%
and ≤10 μV output offset result from the latest Analog Devices,
Inc., technology. The crest factor error is <0.5% for CF values
between 1 and 10.
The precision dc output buffer minimizes errors when driving
low impedance loads with extremely low offset voltages, thanks
to internal bias current cancellation. Unlike digital solutions, the
AD8436 has no switching circuitry limiting performance at high or
low amplitudes (see Figure 2). A usable response of <100 μV
and >3 V extends the dynamic range with no external scaling,
accommodating demanding low level signal conditions and
allowing ample overrange without clipping.
GREATER INPUT DYNAMIC RANGE
The AD8436 delivers true rms results at less cost than misleading
peak, averaging, or digital solutions. There is no programming
expense or processor overhead to consider, and the 4 mm 4 mm
package easily fits into tight applications. On-board buffer
amplifiers enable the widest range of options for any rms-to-dc
converter available, regardless of cost. For minimal applications,
only a single external averaging capacitor is required. The built-in
high impedance FET buffer provides an interface for external
attenuators, frequency compensation, or driving low impedance
loads. A matched pair of internal resistors enables an easily
configurable gain-of-two or more, extending the usable input
range even lower. The low power, precision input buffer makes
the AD8436 attractive for use in portable multi-meters and
other battery-powered applications.
AD8436
∆Σ SOLUTION
100µV
1mV
10mV
100mV
1V
3V
Figure 2. Usable Dynamic Range of the AD8436 vs. ΔΣ
The AD8436 operates from single or dual supplies of 2.4 V
(4.8 V) to 18 V (36 V). A and J grades are available in a compact
4 mm × 4 mm, 20-lead chip-scale package; A and B grades are
available in a 20-lead QSOP package. The operating temperature
ranges are −40°C to 125°C for A and B grades and 0°C to 70°C
for J grade.
Rev. E
Document Feedback
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rights of third parties that may result from its use. Specifications subject to change without notice. No
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Tel: 781.329.4700 ©2011–2017 Analog Devices, Inc. All rights reserved.
Technical Support
www.analog.com
AD8436
Data Sheet
TABLE OF CONTENTS
Features .............................................................................................. 1
Theory of Operation ...................................................................... 10
Overview ..................................................................................... 10
Applications Information.............................................................. 12
Using the AD8436...................................................................... 12
Additional Information ............................................................. 15
AD8436 Evaluation Board ............................................................ 17
Outline Dimensions....................................................................... 20
Ordering Guide .......................................................................... 21
Functional Block Diagram .............................................................. 1
General Description......................................................................... 1
Revision History ............................................................................... 2
Specifications..................................................................................... 3
Absolute Maximum Ratings............................................................ 4
ESD Caution.................................................................................. 4
Pin Configurations and Function Descriptions ........................... 5
Typical Performance Characteristics ............................................. 6
Test Circuits....................................................................................... 9
REVISION HISTORY
3/2017—Rev. D to Rev. E
7/2012—Rev. 0 to Rev. A
Changed CP-20-10 to CP-20-8 .................................... Throughout
Changes to Outline Dimensions................................................... 21
Changes to Ordering Guide .......................................................... 22
Added 20-Lead QSOP .......................................................Universal
Changes to Features Section and General Description Section..1
Changes to Table 1.............................................................................3
Changes to Table 2.............................................................................4
Changes to Table 3 and added Figure 4 and added Table 4;
Renumbered Sequentially ................................................................5
Changes to Equation 1 and change to Column One Heading
in Table 5.......................................................................................... 10
Changes to Averaging Capacitor Considerations—RMS
Accuracy and to Post Conversion Ripple Reduction Filter
and changes to Figure 27 Caption................................................ 12
Changes to Figure 30 to Figure 32................................................ 13
Changes to Using the FET Input Buffer Section and Using the
Output Buffer Section.................................................................... 14
Changes to Figure 38 and Figure 41 and added Converting
to Rectified Average Value Section .............................................. 15
Changes to Figure 41...................................................................... 16
Changes to Figure 42 to Figure 46................................................ 17
Changes to Figure 47 and Figure 48............................................. 18
Updated Outline Dimensions....................................................... 19
Changes to Ordering Guide.......................................................... 20
10/2015—Rev. C to Rev. D
Changes to Figure 5 to Figure 8...................................................... 6
7/2015—Rev. B to Rev. C
Changes to Table 2............................................................................ 4
Changes to Figure 5 to Figure 7...................................................... 6
Changes to Figure 21........................................................................ 9
Changes to Using the FET Input Buffer Section ........................ 14
Changes to Single-Supply Section and Figure 39....................... 15
Added Additional Information Section....................................... 15
Changes to AD8436 Evaluation Board Section and A Word
About Using the AD8436 Evaluation Board Section................... 17
Added Single-Supply Operation Section..................................... 17
Changes to Ordering Guide .......................................................... 21
1/2013—Rev. A to Rev. B
Added B Grade Throughout .............................................Universal
Changes to Figure 1 and changes to General Description.......... 1
Changes to Table 1............................................................................ 3
Changes to Figure 3 ......................................................................... 5
Changes to Figure 9 and Figure 10................................................. 6
Changes to FET Input Buffer Section.......................................... 11
Changes to Averaging Capacitor Considerations—RMS
Accuracy Section and changes to Figure 28................................ 12
Deleted Capacitor Construction Section; added CAVG
7/2011—Revision 0: Initial Version
Capacitor Styles Section................................................................. 13
Added Converting to Average Rectified Value Section............. 15
Changes to Figure 41...................................................................... 16
Changes to Evaluation Board Section.......................................... 17
Changes to Figure 48...................................................................... 19
Changes to Outline Dimensions................................................... 20
Changes to Ordering Guide .......................................................... 21
Rev. E | Page 2 of 21
Data Sheet
AD8436
SPECIFICATIONS
eIN = 300 mV (rms), frequency = 1 kHz sinusoidal, ac-coupled, VS = 5 V, TA = 25°C, CAVG = 10 μF, unless otherwise specified.
Table 1.
AD8436A, AD8436J
Typ
AD8436B
Typ
Parameter
Test Conditions/Comments
Min
Max
Min
Max
Unit
RMS CORE
Conversion Error
Vs. Temperature
Vs. Rail Voltage
Input VOS
Default conditions
−4ꢀ°C < T < 125 C
2.4 V to 18 V
1ꢀ − ꢀ.5
−5ꢀꢀ
ꢀ
ꢀ
1ꢀ + ꢀ.5
+5ꢀꢀ
1ꢀ − ꢀ.25
ꢀ
ꢀ
1ꢀ + ꢀ.25 μV/% rdg
ꢀ.ꢀꢀ6
ꢀ.ꢀ13
ꢀ.ꢀꢀ6
ꢀ.ꢀ13
%/°C
%/V
DC-coupled
ꢀ
−25ꢀ
ꢀ
+25ꢀ
μV
V
Output VOS
AC-coupled input
−4ꢀ C < T < 125°C
DC-coupled, VIN = 3ꢀꢀ mV
eIN = 2 mV to 5ꢀꢀ mV ac
(Additional)
ꢀ
ꢀ
Vs. Temperature
DC Reversal Error
Nonlinearity
Crest Factor Error
1 < CF < 1ꢀ
ꢀ.3
ꢀ
ꢀ.3
ꢀ
μV/°C
%
−1.5
+1.5
−1.ꢀ
+1.ꢀ
ꢀ.2
ꢀ.2
%
CCF = ꢀ.1 μF
−ꢀ.5
+ꢀ.5
−ꢀ.5
+ꢀ.5
%
V
Peak Input Voltage
Input Resistance
Response
−VS − ꢀ.7
7.92
+VS + ꢀ.7
8.ꢀ8
−VS − ꢀ.7
7.92
+VS + ꢀ.7
8.ꢀ8
8
8
kΩ
VIN = 3ꢀꢀ mV rms
(Additional)
1% Error
65
1
65
1
kHz
3 dB Bandwidth
Settling Time
ꢀ.1%
MHz
Rising/falling
Rising/falling
148/341
158/35ꢀ
16
148/341
158/35ꢀ
16
ms
ms
kΩ
μA
ꢀ.ꢀ1%
Output Resistance
Supply Current
INPUT BUFFER
Voltage Swing
Input
15.68
16.32
365
15.68
16.32
365
No input
325
325
G = 1
AC- or dc-coupled
AC-coupled to Pin RMS
−VS
+VS
−VS
+VS
V
Output
−VS + ꢀ.2
−1
+VS − ꢀ.2
+1
−VS + ꢀ.2
−ꢀ.5
+VS − ꢀ.2
+ꢀ.5
5ꢀ
mV
mV
pA
Ω
Offset Voltage
Input Bias Current
Input Resistance
Response
ꢀ
ꢀ
5ꢀ
1ꢀ12
1ꢀ12
(Frequency)
ꢀ.1 dB
95ꢀ
2.1
95ꢀ
2.1
kHz
MHz
μA
3 dB Bandwidth
Supply Current
Optional Gain Resistor
Gain Error
1ꢀꢀ
16ꢀ
+1ꢀ
2ꢀꢀ
1ꢀꢀ
16ꢀ
+1ꢀ
2ꢀꢀ
−9.9
+1ꢀ.1
ꢀ.ꢀ5
−9.9
+1ꢀ.1
ꢀ.ꢀ5
kΩ
G = ×1
%
OUTPUT BUFFER
Offset Voltage
Input Current (IB)
Output Swing
Output Drive Current
Gain Error
RL =
Connected to Pin OUT
−2ꢀꢀ
ꢀ
2
+2ꢀꢀ
51
−15ꢀ
ꢀ
2
+15ꢀ
51
μV
nA
V
(Voltage)
−VS + 5ꢀe−6
−ꢀ.5 (sink)
ꢀ.ꢀꢀ3
+VS − 1
−VS + 5ꢀe−6
+VS − 1
+15 (source) −ꢀ.5 (sink)
+15 (source) mA
%
ꢀ.ꢀ1
4ꢀ
ꢀ.ꢀꢀ3
ꢀ.ꢀ1
4ꢀ
Supply Current
SUPPLY VOLTAGE
Dual
7ꢀ
7ꢀ
μA
2.4
4.8
18
36
2.4
4.8
18
36
V
V
Single
1 IB max measured at power up. Settles to typical value in <15 seconds.
Rev. E | Page 3 of 21
AD8436
Data Sheet
ABSOLUTE MAXIMUM RATINGS
Table 2.
Stresses at or above those listed under Absolute Maximum
Ratings may cause permanent damage to the product. This is a
stress rating only; functional operation of the product at these
or any other conditions above those indicated in the operational
section of this specification is not implied. Operation beyond
the maximum operating conditions for extended periods may
affect product reliability.
Parameter
Voltage
Supply Voltage
Rating
18 V
Input Voltage Range1
Differential Input
Current
VEE − ꢀ.3 V to VCC + ꢀ.3 V
VCC and VEE
Input Current1
1ꢀ mA
Indefinite
ESD CAUTION
Output Short-Circuit Duration
Power Dissipation
CP-2ꢀ-8 LFCSP Without Thermal Pad
CP-2ꢀ-8 LFCSP With Thermal Pad
RQ Package
1.2 W
2.1 W
1.1 W
Temperature
Operating Range
Storage Range
−4ꢀ°C to +125°C
−65°C to +125°C
3ꢀꢀ°C
Lead Soldering (6ꢀ sec)
2
θJA
CP-2ꢀ-8 LFCSP Without Thermal Pad
CP-2ꢀ-8 LFCSP With Thermal Pad
RQ-2ꢀ Package
86°C/W
48°C/W
95°C/W
2 kV
ESD Rating
1 Input pins have clamp diodes to the power supply pins. Limit input current
to 1ꢀ mA or less whenever input signals exceed the power supply rail by ꢀ.3 V.
2 θJA is specified for the worst-case conditions, that is, a device soldered in a circuit
board for surface-mount packages.
Rev. E | Page 4 of 21
Data Sheet
AD8436
PIN CONFIGURATIONS AND FUNCTION DESCRIPTIONS
SUM
20
CAVG
CCF
VCC
IBUFV+
16
1
2
20
19
18
17
16
15
14
13
12
11
SUM
DNC
CAVG
CCF
1
15
3
RMS
VCC
DNC
RMS
OBUFV+
OBUFOUT
OBUFIN–
OBUFIN+
IGND
AD8436
TOP VIEW
(Not to Scale)
4
IBUFOUT
IBUFIN–
IBUFIN+
IBUFGN
DNC
IBUFV+
OBUFV+
OBUFOUT
OBUFIN–
OBUFIN+
IGND
PIN 1
INDICATOR
5
6
AD8436
7
TOP VIEW
IBUFOUT
IBUFIN–
IBUFIN+
(Not to Scale)
8
9
OGND
OUT
10
VEE
NOTES
1. DNC = DO NOT CONNECT.
DO NOT CONNECT TO THIS PIN.
5
11
6
10
IBUFGN DNC
OGND
OUT
VEE
NOTES
1. DNC = DO NOT CONNECT. DO NOT CONNECT TO THIS PIN.
2. THE EXPOSED PAD CONNECTION IS OPTIONAL.
Figure 3. Pin Configuration, Top View, CP-20-8
Figure 4. Pin Configuration, RQ-20
Table 3. Pin Function Descriptions, CP-20-8
Pin No. Mnemonic Description
Table 4. Pin Function Descriptions, RQ-20
Pin No. Mnemonic Description
1
2
3
4
5
6
7
8
DNC
RMS
Do Not Connect. Used for factory test.
AC Input to the RMS Core.
FET Input Buffer Output Pin.
FET Input Buffer Inverting Input Pin.
FET Input Buffer Noninverting Input Pin.
Optional 1ꢀ kΩ Precision Gain Resistor.
Do Not Connect. Used for factory test.
Internal 16 kΩ I-to-V Resistor.
1
2
3
4
5
6
7
8
SUM
DNC
RMS
Summing Amplifier Input Pin.
Do Not Connect. Used for factory test.
AC Input to the RMS Core.
IBUFOUT
IBUFIN−
IBUFIN+
IBUFGN
DNC
OGND
OUT
VEE
IBUFOUT
IBUFIN−
IBUFIN+
IBUFGN
DNC
OGND
OUT
VEE
FET Input Buffer Output Pin.
FET Input Buffer Inverting Input Pin.
FET Input Buffer Noninverting Input Pin.
Optional 1ꢀ kΩ Precision Gain Resistor.
Do Not Connect. Used for factory test.
Internal 16 kΩ I-to-V Resistor.
RMS Core Voltage or Current Output.
Negative Supply Rail.
Half Supply Node.
Output Buffer Noninverting Input Pin.
Output Buffer Inverting Input Pin.
Output Buffer Output Pin.
Power Pin for the Output Buffer.
Power Pin for the Input Buffer.
Positive Supply Rail for the RMS Core.
Connection for Crest Factor Capacitor.
Connection for Averaging Capacitor.
9
RMS Core Voltage or Current Output.
Negative Supply Rail.
Half Supply Node.
9
1ꢀ
11
12
13
14
15
16
17
18
19
2ꢀ
EP
1ꢀ
11
12
13
14
15
16
17
18
19
2ꢀ
IGND
OBUFIN+
OBUFIN−
OBUFOUT
OBUFV+
IBUFV+
VCC
CCF
CAVG
SUM
DNC
Output Buffer Noninverting Input Pin.
Output Buffer Inverting Input Pin.
Output Buffer Output Pin.
Power Pin for the Output Buffer.
Power Pin for the Input Buffer.
Positive Supply Rail for the RMS Core.
Connection for Crest Factor Capacitor.
Connection for Averaging Capacitor.
Summing Amplifier Input Pin.
IGND
OBUFIN+
OBUFIN−
OBUFOUT
OBUFV+
IBUFV+
VCC
CCF
CAVG
Exposed Pad Connection to Ground
Pad Optional.
Rev. E | Page 5 of 21
AD8436
Data Sheet
TYPICAL PERFORMANCE CHARACTERISTICS
TA = 25°C, VS = 5 V, CAVG = 10 μF, 1 kHz sine wave, unless otherwise indicated.
5V
5V
1V
V
= ±5V
S
1V
100mV
10mV
1mV
100mV
10mV
1mV
−3dB ERROR
±1% ERROR
±10% ERROR
–3dB ERROR
V
S
= 4.8V
1M
100µV
50µV
100µV
50µV
50 100
1k
10k
100k
1M
5M
50 100
1k
10k
100k
5M
FREQUENCY (Hz)
FREQUENCY (Hz)
Figure 5. RMS Core Frequency Response (See Figure 21)
Figure 8. RMS Core Frequency Response with VS = +4.8 V (See Figure 22)
5V
15
eIN = 3.5mV rms
12
1V
100mV
10mV
1mV
9
GAIN = 6dB
6
3
GAIN = 0dB
0
–3
–6
±1% ERROR
±10% ERROR
–3dB ERROR
–9
–12
–15
V
= ±2.4V
1M
100µV
50µV
S
100
1k
10k
100k
1M
5M
50 100
1k
10k
100k
5M
FREQUENCY (Hz)
FREQUENCY (Hz)
Figure 6. RMS Core Frequency Response with VS = 2.4 V (See Figure 21)
Figure 9. Input Buffer, Small Signal Bandwidth at 0 dB and 6 dB Gain
5V
1V
15
eIN = 300mV rms
12
9
GAIN = 6dB
6
100mV
10mV
3
GAIN = 0dB
0
–3
–6
±1% ERROR
±10% ERROR
–3dB ERROR
1mV
–9
–12
–15
V
= ±15V
1M
100µV
50µV
S
100
1k
10k
100k
1M
5M
50 100
1k
10k
100k
5M
FREQUENCY (Hz)
FREQUENCY (Hz)
Figure 7. RMS Core Frequency Response with VS = 15 V (See Figure 21)
Figure 10. Input Buffer, Large Signal Bandwidth at 0 dB and 6 dB Gain
Rev. E | Page 6 of 21
Data Sheet
AD8436
10
5
15
eIN = 3.5mV rms
P
= 100µs
W
12
9
6
CAVG = 10µF
CCF = 0.1µF
3
0
0
–3
–6
–9
–12
–15
CAVG = 10µF
−5
−10
100
1k
10k
100k
1M
5M
0
2
4
6
8
10
CREST FACTOR RATIO
FREQUENCY (Hz)
Figure 14. Crest Factor Error vs. Crest Factor for CAVG and CAVG and CCF
Capacitor Combinations
Figure 11. Output Buffer, Small Signal Bandwidth
1.00
0.75
0.50
0.25
0
0.5
0.4
CAVG = 10µF
8 SAMPLES
0.3
0.2
0.1
0
–0.1
–0.2
–0.3
–0.4
–0.5
−0.25
−0.50
−0.75
−1.00
–50
–25
0
25
50
75
100
125
0
2
4
6
8
10
12
14
16
18
20
TEMPERATURE (°C)
SUPPLY VOLTAGE (±V)
Figure 15. Additional Conversion Error vs. Temperature
Figure 12. Additional Error vs. Supply Voltage
2.5
2.0
1.5
1.0
0.5
0
2.0
1.6
1.2
0.8
0.4
0
V
= ±15V
S
V
= ±5V
S
V
= ±2.4V
S
0
0.5
1.0
INPUT VOLTAGE (V rms)
1.5
2.0
0
16
2
4
6
8
10
12
14
18
SUPPLY VOLTAGE (±V)
Figure 16. RMS Core Supply Current vs. Input for VS = 2.4 V, 5 V, and 15 V
Figure 13. Core Input Voltage for 1% Error vs. Supply Voltage
Rev. E | Page 7 of 21
AD8436
Data Sheet
250
200
150
100
50
90
80
70
60
50
40
30
20
10
0
0
−50
−100
−150
−200
−250
−10
−50
−50
−25
0
25
50
75
100
125
−25
0
25
50
75
100
125
TEMPERATURE (°C)
TEMPERATURE (°C)
Figure 17. FET Input Buffer Bias Current vs. Temperature
Figure 19. Output Buffer VOS vs. Temperature
1000
CAVG = 10µF
1kHz 300mV rms BURST INPUT
750
500
0V
250
0
300mV DC OUT
−250
−500
−750
−1000
0V
0V
1kHz 1mV rms BURST INPUT
1mV DC OUT
−50
−25
0
25
50
75
100
125
0V
TEMPERATURE (°C)
TIME (50ms/DIV)
Figure 18. Input Offset Voltage of FET Buffer vs. Temperature
Figure 20. Transition Times with 1 kHz Burst at Two Input Levels
(See Theory of Operation Section)
Rev. E | Page 8 of 21
Data Sheet
AD8436
TEST CIRCUITS
CALIBRATOR
(50Hz<f<500kHz)
ATTENUATOR
eIN = 100µV, 300µV
10µF +5V
VCC
CAV
100kΩ
22µF
RMS
PRECISION DMM
IGND
RMS CORE
FUNCTION GENERATOR
(f>500kHz)
100kΩ
16kΩ
OGND
OUT
10µF
VEE
–5V
PRECISION DMM
Figure 21. Core Response Test Circuit Using Dual Supplies
SIGNAL SOURCE
10µF 4.80V
CAV
VCC
4.7µF
RMS
100kΩ
100kΩ
RMS CORE
IGND
AC-IN MONITOR
4.7µF
16kΩ
PRECISION DMM
PRECISION DMM
OUT
OGND
VEE
Figure 22. Core Response Test Circuit Using a Single Supply
10µF +5V
FUNCTION GENERATOR
CAV
VCC
4.7µF
RMS
100kΩ
100kΩ
RMS CORE
IGND
AC-IN MONITOR
PRECISION DMM
16kΩ
OGND
VEE
OUT
–5V
PRECISION DMM
Figure 23. Crest Factor Test Circuit
Rev. E | Page 9 of 21
AD8436
Data Sheet
THEORY OF OPERATION
RMS Core
OVERVIEW
The core consists of a voltage-to-current converter (precision
resistor), absolute value, and translinear sections. The translinear
section exploits the properties of the bipolar transistor junctions
for squaring and root extraction (see Figure 24). The external
capacitor (CAVG) provides for averaging the product. Figure 20
shows that there is no effect of signal input on the transition times,
as seen in the dc output. Although the rms core responds to input
voltages, the conversion process is current sensitive. If the rms
input is ac-coupled, as recommended, there is no output offset
voltage, as reflected in Table 1. If the rms input is dc-coupled, the
input offset voltage is reflected in the output and can be calibrated
as with any fixed error.
The AD8436 is an implicit function rms-to-dc converter that
renders a dc voltage dependent on the rms (heating value) of an
ac voltage. In addition to the basic converter, this highly integrated
functional circuit block includes two fully independent, optional
amplifiers, a standalone FET input buffer amplifier, and a precision
dc output buffer amplifier (see Figure 1). The rms core includes
a precision current responding full-wave rectifier and a log-
antilog transistor array for current squaring and square rooting
to implement the classic expression for rms (see Equation 1).
For basic applications, the converter requires only an external
capacitor, for averaging (see Figure 31). The optional on-board
amplifiers offer utility and flexibility in a variety of applications
without incurring additional circuit board footprint. For lowest
power, the amplifier supply pins are left unconnected.
V+
Why RMS?
The rms value of an ac voltage waveform is equal to the dc
voltage providing the same heating power to a load. A common
measurement technique for ac waveforms is to rectify the signal
in a straightforward way using a diode array of some sort, resulting
in the average value. The average value of various waveforms (sine,
square, and triangular, for example) varies widely; true rms is the
only metric that achieves equivalency for all ac waveforms. See
Table 5 for non-rms-responding circuit errors.
+
OUT
5kꢀ CAVG
AC IN
V-TO-I
ABSOLUTE
VALUE
CIRCUIT
V+
16kꢀ
V–
The acronym rms means “root-mean-square” and reads as follows:
“the square root of the average of the sum of the squares” of the
peak values of any waveform. RMS is shown in the following
equation:
Figure 24. RMS Core Block Diagram
2
1 T
erms
V
t
dt
(1)
T
0
For additional information, select Section I of the second edition of
the Analog Devices RMS-to-DC Applications Guide.
Table 5. General AC Parameters
Reading of an Average Value Circuit
Calibrated to an RMS Sine Wave
Waveform Type (1 V Peak)
Crest Factor
RMS Value
ꢀ.7ꢀ7
1.ꢀꢀ
ꢀ.577
ꢀ.333
ꢀ.5
Error (%)
Sine
1.414
1.ꢀꢀ
1.73
3
2
1ꢀ
ꢀ.7ꢀ7
1.11
ꢀ.555
ꢀ.295
ꢀ.278
ꢀ.ꢀ11
ꢀ
11.ꢀ
−3.8
Square
Triangle
Noise
Rectangular
Pulse
SCR
DC = 5ꢀ%
DC = 25%
−11.4
−44
−89
−28
−3ꢀ
ꢀ.1
2
4.7
ꢀ.495
ꢀ.212
ꢀ.354
ꢀ.15ꢀ
Rev. E | Page 1ꢀ of 21
Data Sheet
AD8436
The 16 kΩ resistor in the output converts the output current to
a dc voltage that can connect to the output buffer or to the
circuit that follows. The output appears as a voltage source in
series with 16 kΩ. If a current output is desired, the resistor
connection to ground is left open and the output current is
applied to a subsequent circuit, such as the summing node of
a current summing amplifier. Thus, the core has both current
and voltage outputs, depending on the configuration. For a
voltage output with 0 Ω source impedance, use the output
buffer. The offset voltage of the buffer is 25 ꢀV or 50 ꢀV,
depending on the grade.
The output buffer can be configured as a single or two-pole low-
pass filter using circuits shown in the Applications Information
section. Residual output ripple is reduced, without affecting the
converted dc output. As the response approaches the low frequency
end of the bandwidth, the ripple rises, dependent on the value
of the averaging capacitor. Figure 27 shows the effects of four
combinations of averaging and filter capacitors. Although the
filter capacitor reduces the ripple for any given frequency, the dc
error is unaffected. Of course, a larger value averaging capacitor can
be selected, at a larger cost. The advantage of using a low-pass filter
is that a small value of filter capacitor, in conjunction with the
16 kꢁ output resistor, reduces ripple and permits a smaller
averaging capacitor, effecting a cost savings. The recommended
capacitor values for operation to 40 Hz are 10 μF for averaging
and 3.3 μF for filter.
FET Input Buffer
Because the V-to-I input resistor value of the AD8436 rms core
is 8 kꢁ, a high input impedance buffer is often used between
rms-to-dc converters and finite impedance sources. The optional
JFET input op amp minimizes attenuation and uncouples common
input amenities, such as resistive voltage dividers or resistors used
to terminate current transformers. The wide bandwidth of the
FET buffer is well matched to the rms core bandwidth so that
no information is lost due to serial bandwidth effects. Although
the input buffer consumes little current, the buffer supply is
independently accessible and can disconnect to reduce power.
Dynamic Range
The AD8436 is a translinear rms-to-dc converter with exceptional
dynamic range. Although accuracy varies slightly more at the
extreme input values, the device still converts with no spurious
noise or dropout. Figure 25 is a plot of the rms/dc transfer function
near zero voltage. Unlike processor or other solutions, residual
errors at very low input levels can be disregarded for most
applications.
Optional matched 10 kꢁ input and feedback resistors are provided
on chip. Consult the Applications Information section to learn
how to use these resistors. The 3 dB bandwidth of the input
buffer is 2.7 MHz at 10 mV rms input and approximately 1.5 MHz
at 1 V rms. The amplifier gain and bandwidth are sufficient for
applications requiring modest gain or response enhancement to
a few hundred kilohertz (kHz), if desired. Configurations of the
input buffer are discussed in the Applications Information section.
30
∆Σ OR OTHER DIGITAL
SOLUTIONS CANNOT
WORK AT ZERO
VOLTS
20
10
0
AD8436
SOLUTION
Precision Output Buffer
The precision output buffer is a bipolar input amplifier, laser
trimmed to cancel input offset voltage errors. As with the input
buffer, the supply current is very low (<50 ꢀA, typically), and
the power can be disconnected for power savings if the buffer is
not needed. Be sure that the noninverting input is also
–30
–20
–10
0
10
20
30
INPUT VOLTAGE (mV DC)
Figure 25. DC Transfer Function near Zero
disconnected from the core output (OUT) if the buffer supply
pin is disconnected. Although the input current of the buffer is
very low, a laser-trimmed 16 kΩ resistor, connected in series
with the inverting input, offsets any self-bias offset voltage.
Rev. E | Page 11 of 21
AD8436
Data Sheet
APPLICATIONS INFORMATION
Ripple is reduced by increasing the value of the averaging
USING THE AD8436
capacitor, or by postconversion filtering. Ripple reduction
following conversion is far more efficient because the ripple
average value has converted to its rms value. Capacitor values for
post-conversion filtering are significantly less than the equivalent
averaging capacitor value for the same level of ripple reduction.
This approach requires only a single capacitor connected to the
OUT pin (see Figure 26). The capacitor value correlates to the
simple frequency relation of ½ π R-C, where R is fixed at 16 kꢁ.
This section describes the power supply and feature options,
as well as the function and selection of averaging and filter
capacitor values. Averaging and filtering options are shown
graphically and apply to all circuit configurations.
Averaging Capacitor Considerations—RMS Accuracy
Typical AD8436 applications require only a single external
capacitor (CAVG) connected to the CAVG pin (see Figure 31).
The function of the averaging capacitor is to compute the mean
(that is, average value) of the sum of the squares. Averaging
(that is, integration) follows the rms core, where the input
current is squared. The mean value is the average value of the
squared input voltage over several input waveform periods. The
rms error is directly affected by the number of periods averaged, as
is the resultant peak-to-peak ripple.
OUT
CORE
DC OUTPUT
CLPF
9
16kꢀ
OGND
8
Figure 26. Simple One-Pole Post Conversion Filter
The result of the conversion process is a dc component and a
ripple component whose frequency is twice that of the input. The
rms conversion accuracy depends on the value of CAVG, so the
value selected need only be large enough to average enough periods
at the lowest frequency of interest to yield the required rms
accuracy.
As seen in Figure 27, CAVG alone determines the rms error, and
CLPF serves purely to reduce ripple. Figure 27 shows a constant
rms error for CLPF values of 0.33 μF and 3.3 μF; only the ripple
is affected.
1
CAVG = 10µF
CLPF = 0.33µF OR 3.3µF
0
Figure 28 is a plot of rms error vs. frequency for various averaging
capacitor values. To use Figure 28, simply locate the frequency
of interest and acceptable rms error on the horizontal and vertical
scales, respectively. Then choose or estimate the next highest
capacitor value adjacent to where the frequency and error lines
intersect (for an example, see the orange circle in Figure 28).
–1
–2
–3
–4
–5
Post Conversion Ripple Reduction Filter
–6
CAVG = 1µF
Input rectification included in the AD8436 introduces a residual
ripple component that is dependent on the value of CAVG and
twice the input signal frequency for symmetrical input waveforms.
For sampling applications such as a high resolution ADC, the ripple
component may cause one or more LSBs to cycle, and low value
display numerals to flash.
–7
–8
CLPF = 0.33µF OR 3.3µF
–9
–10
10
100
1k
FREQUENCY (Hz)
Figure 27. RMS Error vs. Frequency for Two Values of CAVG and CLPF
(Note that only CAVG value affects rms error; CLPF has no effect.)
0
–0.5
–1.0
–1.5
–2.0
SEE
TEXT
CAVG = 0.22µF
2
10
100
1k
FREQUENCY (Hz)
Figure 28. Conversion Error vs. Frequency for Various Values of CAVG
Rev. E | Page 12 of 21
Data Sheet
AD8436
For simplicity, Figure 29 shows ripple vs. frequency for four
combinations of CAVG and CLPF.
X8L grade MLCs are rated for high temperatures (125°C or 150°C),
but are available only up to 10 ꢀF. Never use electrolytic capacitors,
or X7R or lower grade ceramics.
1
AC INPUT = 300mV rms
Basic Core Connections
CAVG = 1µF, CLPF = 0.33µF
CAVG = 1µF, CLPF = 3.3µF
CAVG = 10µF, CLPF = 0.33µF
Many applications require only a single external capacitor for
averaging. A 10 μF capacitor is more than adequate for acceptable
rms errors at line frequencies and below.
CAVG = 10µF, CLPF = 3.3µF
0.1
0.01
The signal source sees the input 8 kΩ voltage-to-current conversion
resistor at Pin RMS; thus, the ideal source impedance is a voltage
source (0 Ω source impedance). If a non-zero signal source
impedance cannot be avoided, be sure to account for any series
connected voltage drop.
0.001
0.0001
An input coupling capacitor must be used to realize the near-zero
output offset voltage feature of the AD8436. Select a coupling
capacitor value that is appropriate for the lowest expected operating
frequency of interest. As a rule of thumb, the input coupling
capacitor can be the same as or half the value of the averaging
capacitor because the time constants are similar. For a 10 ꢀF
averaging capacitor, a 4.7 ꢀF or 10 ꢀF tantalum capacitor is a
good choice (see Figure 31).
10
100
INPUT FREQUENCY (Hz)
1k
Figure 29. Residual Ripple Voltage for Various Filter Configurations
Figure 30 shows the effects of averaging and post-rms filter
capacitors on transition and settling times using a 10-cycle,
50 Hz, 1 second period burst signal input to demonstrate time-
domain behavior. In this instance, the averaging capacitor value
was 10 μF, yielding a ripple value of 6 mV rms. A postconversion
capacitor (CLPF) of 0.68 ꢀF reduced the ripple to 1 mV rms. An
averaging capacitor value of 82 ꢀF reduced the ripple to 1 mV
but extended the transition time (and cost) significantly.
+5V
CAVG
+*
10µF
19
17
CAVG
VCC
4.7µF
OR 10µF
+*
2
RMS AD8436 OUT
IGND VEE OGND
9
INPUT
50Hz 10 CYCLE BURST
400mv/DIV
11
10
8
CAVG = 10µF FOR BOTH PLOTS,
BUT RED PLOT HAS NO LOW-PASS FILTER,
GREEN PLOT HAS CLPF = 0.68µF
10mV/DIV
–5V
*FOR POLARIZED CAPACITOR STYLES.
Figure 31. Basic Applications Circuit
Using a Capacitor for High Crest Factor Applications
CAVG = 82µF
The AD8436 contains a unique feature to reduce large crest
factor errors. Crest factor is often overlooked when considering
the requirements of rms-to-dc converters, but it is very important
when working with signals with spikes or high peaks. The crest
factor is defined as the ratio of peak voltage to rms. See Table 5
for crest factors for some common waveforms.
TIME (100ms/DIV)
Figure 30. Effects of Various Filter Options on Transition Times
CAVG Capacitor Styles
+5V
CAVG
When selecting a capacitor style for CAVG there are certain
tradeoffs.
+*
CCF
10µF
0.1µF
For general usage, such as most DMM or power measurement
applications where input amplitudes are typically greater than
1 mV, surface mount tantalums are the best overall choice for
space, performance, and economy.
19
18
17
CAVG CCF
VCC
4.7µF
OR 10µF
+*
2
9
RMS AD8436 OUT
IGND VEE OGND
For input amplitudes less than around a millivolt, low dc leakage
capacitors, such as film or X8L MLCs, maintain rms conversion
accuracy. Metalized polyester or similar film styles are best, as
long as the temperature range is appropriate.
11
10
8
–5V
*FOR POLARIZED CAPACITOR STYLES.
Figure 32. Connection for Additional Crest Factor Performance
Rev. E | Page 13 of 21
AD8436
Data Sheet
Crest factor performance is mostly applicable for unexpected
waveforms such as switching transients in switchmode power
supplies. In such applications, most of the energy is in these peaks
and can be destructive to the circuitry involved, although the
average ac value can be quite low.
Because the 10 kΩ resistors are closely matched and trimmed to
a high tolerance, the input buffer gain can increase to several
hundred with an external resistor connected to Pin IBUFIN−.
The bandwidth diminishes at the typical rate of a decade per 20 dB
of gain, and the output voltage range is constrained. The small-
signal response, shown in Figure 9, serves as a guide. For example,
if detecting small input signals at power line frequencies, an
external 100 ꢁ resistor connected from IBUFIN− to ground sets
the gain to 101 and the 3 dB bandwidth to ~15 kHz, which is
adequate for amplifying power line frequencies.
Figure 14 shows the effects of an additional crest factor capacitor of
0.1 ꢀF and an averaging capacitor of 10 ꢀF. The larger capacitor
serves to average the energy over long spaces between pulses,
while the CCF capacitor charges and holds the energy within
the relatively narrow pulse.
Using the FET Input Buffer
Using the Output Buffer
The on-chip FET input buffer is an uncommitted FET input
op amp used for driving the 8 kꢁ I-to-V input resistor of the
rms core. Pin IBUFOUT, Pin IBUFIN−, and Pin IBUFIN+ are
the input/output; Pin IBUFINGN is an optional connection for
gain in the input buffer; and Pin IBUFV+ connects power to the
buffer. Connecting Pin IBUFV+ to the positive rail is the only
power connection required because the negative rail is internally
connected. Because the input stage is a FET and the input
impedance must be very high to prevent loading of the source, a
large value (10 Mꢁ) resistor connects from midsupply at Pin IGND
to Pin IBUFIN+ to prevent the input gate from floating high.
The AD8436 output buffer is a precision op amp optimized for
high dc accuracy. Figure 34 shows a block diagram of the basic
amplifier and input/output pins. The amplifier often configures
as a unity gain follower but easily configures for gain, as a
Sallen-Key, low-pass filter (in conjunction with the built-in 16 kΩ
I-to-V resistor). Note that an additional 16 kꢁ on-chip precision
resistor in series with the inverting input of the amplifier balances
output offset voltages resulting from the bias current from the
noninverting amplifier. The output buffer disconnects from
Pin OUT for precision core measurements.
As with the input FET buffer, the amplifier positive supply
disconnects when not needed. In normal circumstances, the
buffers connect to the same supply as the core. Figure 35 shows
the signal connections to the output buffer. Note that the input
offset voltage contribution by the bias currents are balanced by
equal value series resistors, resulting in near zero offset voltage.
OUTPUT BUFFER
For unity gain, connect the IBUFOUT pin to the IBUFIN− pin.
For a gain of 2×, connect the IBUFGN pin to ground. See Figure 9
and Figure 10 for large and small signal responses at the two
built-in gain options.
The offset voltage of the input buffer is ≤500 μV, depending on
grade. A capacitor connected between the buffer output pin
(IBUFOUT) and the RMS pin is recommended so that the
input buffer offset voltage does not contribute to the overall
error. Select the capacitor value for least minimum error at the
lowest operating frequency. Figure 33 is a schematic showing
internal components and pin connections.
OBUFIN+
OBUFIN–
+
–
OBUFOUT
16kꢀ
Figure 34. Output Buffer Block Diagram
IBIAS
OUT
OBUFIN+
CORE
OBUFOUT
9
12
13
+
–
16
14
16kꢀ
RMS
IBUFV+
2
16kꢀ
10µF
OBUFIN–
IBUFOUT
IBUFIN–
IBUFIN+
3
4
5
OGND
8
–
0.47µF
Figure 35. Basic Output Buffer Connections
+
10kꢀ
For applications requiring ripple suppression in addition to the
single-pole output filter described previously, the output buffer
is configurable as a two-pole Sallen-Key filter using two external
resistors and two capacitors. At just over 100 kHz, the amplifier
has enough bandwidth to function as an active filter for low
frequencies such as power line ripple. For a modest savings in
cost and complexity, the external 16 kΩ feedback resistor can be
omitted, resulting in slightly higher VOS (80 ꢀV).
10Mꢀ
10pF
11 IGND
10kꢀ
6
IBUFGN
Figure 33. Connecting the FET Input Buffer
Capacitor coupling at the input and output of the FET buffer is
recommended to avoid transferring the buffer offset voltage to
the output. Although the FET input impedance is extremely high,
the 10 MΩ centering resistor connected to IGND must be taken
into account when selecting an input capacitor value. This is simply
an impedance calculation using the lowest desired frequency, and
finding a capacitor value based on the least attenuation desired.
Rev. E | Page 14 of 21
Data Sheet
AD8436
10µF
2C
19
17
16kꢀ
OBUFIN+
OUT
9
12
13
CORE
+
–
CAV
VCC
14
C
16kꢀ
16kꢀ
2
3
4
5
RMS
AD8436
OBUFOUT
OUT
9
4.7µF
OBUFIN–
OGND
8
IBUFOUT
IBUFIN–
IBUFIN+
16kꢀ
OPTIONAL
AMBIENT
NOISE
0.47µF
IGND 11
Figure 36. Output Buffer Amplifier Configured as a Two-Pole, Sallen-Key
Low-Pass Filter
OGND
VEE
10
FILTER
CAPACITOR
10Mꢀ
8
Configure the output buffer (see Figure 37) to invert dc output.
OUT
16kꢀ
CORE
9
13
12
–
+
Figure 39. Connections for Single-Supply Operation
OBUFIN–
14
16kꢀ
OBUFOUT
OBUFIN+
Recommended Application
OGND
32.4kꢀ
8
Figure 40 shows a circuit for a typical application for frequencies
as low as power line, and above. The recommended averaging,
crest factor and LPF capacitor values are 10 ꢀF, 0.1 ꢀF and 3.3 ꢀF.
Refer to the Using the Output Buffer section if additional low-
pass filtering is required.
Figure 37. Inverting Output Configuration
Current Output Option
If a current output is required, connect the current output,
OUT, to the destination load. To maximize precision, provide a
means for external calibration to replace the internal trimmed
resistor, which is bypassed. This configuration is useful for
convenient summing of the AD8436 result with another
voltage, or for polarity inversion.
VCC
10µF
0.1µF
+
20 19
18
17
16
SUM CAVG CCF VCC IBUFV+
15
14
13
12
11
1
2
DNC
OBUFV+
CAVG
CCF
AD8436
19
18
DC
OUT
RMS
OBUFOUT
OBUFIN–
OBUFIN+
10µF
DIRECTION OF
DC OUTPUT
CURRENT
3
4
5
2kꢀ
IBUFOUT
IBUFIN–
IBUFIN+
(OPTIONAL)
8kꢀ
OUT
RMS
2
9
CORE
15kꢀ
0.47µF
+
IGND
VEE
AC IN
16kꢀ
–
INVERTED DC
VOLTAGE
OUTPUT
10Mꢀ
8
IBUFGN DNC OGND OUT
32.4kꢀ
OGND
6
7
8
9
10
DO NOT CONNECT FOR
CURRENT OUTPUT
VEE
Figure 38. Connections for Current Output Showing Voltage Inversion
3.3µF
Single-Supply
Figure 40. Typical Application Circuit
Connections for single-supply operation are shown in Figure 39
and are similar to those for dual power supply when the device
is ac-coupled. The analog core and buffer inputs are biased at
half the supply voltage, but the output of the OBUFOUT pin
(Pin 14) remains referred to ground because the output of the
AD8436 is a current source. An additional bypass capacitor can
be helpful at Pin 11 (IGND) to suppress potential common-mode
noise. The capacitor value is most likely determined empirically,
but ranges between 0.1 μF and 4.7 μF. The source resistance for the
capacitor is 50 kΩ, the equivalent parallel resistance of the two
internal 100 kΩ resistors (see Figure 1).
Converting to Average Rectified Value
To configure the AD8436 for rectified average instead of rms
conversion, simply reduce the value of CAVG to 470 pF (see
Figure 41). To enable both modes of operation, insert a switch
between capacitor CAVG and Pin CAVG.
ADDITIONAL INFORMATION
The following reference materials provide additional rms-to-dc
converter information relative to the AD8436:
RMS to DC Conversion Application Guide
AN-268 Application Note, RMS-to-DC Converters Ease
Measurement Tasks
AN-1341 Application Note, Using the AD8436 True RMS to
DC Converter
Rev. E | Page 15 of 21
AD8436
Data Sheet
DISCONNECTING CAVG DEFAULTS THE
COMPUTED RESULT TO AVERAGE-VALUE.
A MINIMUM OF 470pF CAPACITANCE IS
REQUIRED TO MAINTAIN STABILITY
VCC
CAPACITOR CAVG COMPUTES THE
MEAN IN THE IMPLICIT RMS
EXPRESSION. FOR SMALL VALUES
OF CAVG, THE AC INPUT WAVEFORM
WILL STILL BE FULLY RECTIFIED AND
APPEAR AT THE OUTPUT.
470pF 0.1µF
+
CAVG
10µF
20 19
18
17
16
SUM CAVG CCF VCC IBUFV+
15
14
13
1
2
DNC
OBUFV+
AD8436
DC
OUT
RMS
OBUFOUT
OBUFIN–
OBUFIN+
10µF
3
IBUFOUT
IBUFIN–
IBUFIN+
4
12
11
0.47µF
5
IGND
VEE
AC IN
IBUFGN DNC OGND OUT
10Mꢀ
6
7
8
9
10
VEE
CLPF
3.3µF
CAPACITOR CLPF, IN CONJUNCTION WITH
THE INTERNAL 16kꢀ OUTPUT RESISTOR
FILTERS THE RECTIFIED OUTPUT, YIELDING
THE AVERAGE-RECTIFIED VALUE.
Figure 41. Configuration for Average Rectified Value
Rev. E | Page 16 of 21
Data Sheet
AD8436
AD8436 EVALUATION BOARD
The AD8436-EVALZ provides a platform to evaluate AD8436
performance. The board is fully assembled, tested, and ready to
use after connecting the power and signal sources. Figure 47
is a photograph of the board and Figure 48 is the schematic.
Signal connections are located on the primary and secondary
sides, with power and ground on the inner layers. Figure 42 to
Figure 46 illustrate the various design details of the board,
including basic layout and copper patterns. These figures are
useful references for application designs.
Table 6.
Switch
Function
CORE_BUFFER
Selects core or input buffer for the input
signal
Selects ac or dc coupling to the core
Selects the output buffer or the core
output at the DCOUT BNC
Enables or disables the input buffer
Enables or disables the output buffer
INCOUP
SDCOUT
IBUF_VCC
OBUF_VCC
A Word About Using the AD8436 Evaluation Board
Ample test points provide easy monitoring of inputs and
outputs using standard test equipment. Unity is the input buffer
default gain; for 2× gain, simply install a 0 Ω 0603 resistor (jumper)
at Position R5. For higher IBUF gains, remove the 0 Ω resistor
at Position RFBH (there is an internal 10 kΩ resistor from the
OBUF_OUT to IBUFIN−) and install a smaller value resistor in
Position RFBL. A 100 Ω resistor establishes a gain of 100×.
The AD8436-EVALZ offers many options, without sacrificing
simplicity. The board is tested and shipped with a 10 ꢀF averaging
capacitor (CAVG), a 3.3 ꢀF low-pass filter capacitor (CLPF), and a
0.1 ꢀF capacitor to optimize crest factor (CCF) performance. To
evaluate minimum cost applications, remove both capacitors. The
functions of the five switches are listed in Table 6.
Single-Supply Operation
Referring to Figure 48, single-supply operation requires the
removal of Resistor R6. If needed, an optional capacitor in the
range 0.1 ꢀF to 4.7 ꢀF may be installed in the R6 position for
ambient noise decoupling (this is rarely required, however).
Connect the negative supply pin (VEE) to ground (GND);
otherwise, the negative supply rails remain open.
Rev. E | Page 17 of 21
AD8436
Data Sheet
Figure 45. AD8436-EVALZ Power Plane
Figure 42. Assembly of the AD8436-EVALZ
Figure 43. AD8436-EVALZ Primary Side Copper
Figure 44. AD8436-EVALZ Secondary Side Copper
Figure 46. AD8436-EVALZ Ground Plane
Rev. E | Page 18 of 21
Data Sheet
AD8436
Figure 47. Photograph of the AD8436-EVALZ
3
–V
(GRN)
+V
(RED)
3
C1
GND1 GND2 GND3 GND4 GND5 GND6
CAVG
C2
10µF
CCF
0.1µF
X8R
10µF
+
10µF
50V
C4
0.1µF
TIBUFV+
EN
+
50V
–40°C TO
+125°C
DIS
+
TCAVG
TCCF
18
–40°C TO +125°C
TSUM
VEE
IBUF_VCC
IBUFV+
20
SUM
19
17
VCC
16
INCOUP
CAVG
CCF
VCC
TOBUFV+
15
EN
DIS
AC
DC
DNC
OBUFV+
1
2
CORE_BUF
CORE
OBUF_VCC
CIN
10µF
AC_IN
TOBFOUT
14
TRMSIN
RMS
OBUFOUT
OBUFIN–
OBUFIN+
IGND
+
R8
0ꢀ
BUF
1
C6
2.2µF
TOBUFIN−
13
TIBUFOUT
3
TACIN
IBUFOUT
IBUFIN–
IBUFIN+
AD8436
TDCOUT
BUF
4
RFBH
0ꢀ
DC
OUT
TOBUFIN+
12
TIBFIN–
4
C5
0.47µF
CORE
5
RFBL
SDCOUT
DNI
TIGND
1
C7
1.5µF
TIBFIN+
5
11
1
BUF
R3
R1
10Mꢀ
GAIN
DNC
7
OGND
8
OUT
9
VEE
10
8.06kꢀ
2
R7
6
0ꢀ
3
TBUFGN
TOGND
3
R6
0ꢀ
C3
0.1µF
1
R4
TOUT
4
R5
0ꢀ
R2
0ꢀ
0ꢀ
VEE
CLPF
3.3µF
1
2
3
OPTIONAL COMPONENTS TO CONFIGURE IBUFOUT AS A FILTER.
REMOVE R7 FOR CORE-ONLY TESTS.
FOR SINGLE SUPPLY OPERATION, REMOVE R6, SHORT OR REPLACE C3 WITH A 0ꢀ RESISTOR AND CONNECT THE SUPPLY GROUND OR RETURN TO
THE GREEN TEST LOOP –V.
4
5
TO CONFIGURE THE FET INPUT BUFFER FOR GAIN OF 2, INSTALL 0ꢀ RESISTOR AT R5 AND REMOVE RFBH.
RFBL IS USED TO CONFIGURE THE INPUT BUFFER FOR GAIN VALUES >2×.
Figure 48. Evaluation Board Schematic
Rev. E | Page 19 of 21
AD8436
Data Sheet
OUTLINE DIMENSIONS
DETAIL A
(JEDEC 95)
4.10
4.00 SQ
3.90
0.30
0.25
0.18
PIN 1
INDICATOR
PIN 1
INDIC ATOR AREA OPTIONS
(SEE DETAIL A)
16
20
0.50
BSC
1
15
2.75
2.60 SQ
2.35
EXPOSED
PAD
5
11
10
6
0.50
0.40
0.30
0.25 MIN
TOP VIEW
SIDE VIEW
BOTTOM VIEW
0.80
0.75
0.70
FOR PROPER CONNECTION OF
THE EXPOSED PAD, REFER TO
THE PIN CONFIGURATION AND
FUNCTION DESCRIPTIONS
0.05 MAX
0.02 NOM
COPLANARITY
0.08
SECTION OF THIS DATA SHEET.
SEATING
PLANE
0.20 REF
COMPLIANT TO JEDEC STANDARDS MO-220-WGGD-11.
Figure 49. 20-Lead Lead Frame Chip Scale Package [LFCSP]
4 mm × 4 mm Body and 0.75 mm Package Height
(CP-20-8)
Dimensions shown in millimeters
0.345 (8.76)
0.341 (8.66)
0.337 (8.55)
20
1
11
0.158 (4.01)
0.154 (3.91)
0.244 (6.20)
0.150 (3.81)
0.236 (5.99)
0.228 (5.79)
10
0.010 (0.25)
0.006 (0.15)
0.020 (0.51)
0.010 (0.25)
0.069 (1.75)
0.053 (1.35)
0.065 (1.65)
0.049 (1.25)
0.010 (0.25)
0.004 (0.10)
0.041 (1.04)
REF
SEATING
PLANE
8°
0°
0.025 (0.64)
BSC
0.050 (1.27)
0.016 (0.41)
COPLANARITY
0.004 (0.10)
0.012 (0.30)
0.008 (0.20)
COMPLIANT TO JEDEC STANDARDS MO-137-AD
CONTROLLING DIMENSIONS ARE IN INCHES; MILLIMETER DIMENSIONS
(IN PARENTHESES) ARE ROUNDED-OFF INCH EQUIVALENTS FOR
REFERENCE ONLY AND ARE NOT APPROPRIATE FOR USE IN DESIGN.
Figure 50. 20-Lead Shrink Small Outline Package [QSOP]
(RQ-20)
Dimensions shown in inches and (millimeters)
Rev. E | Page 2ꢀ of 21
Data Sheet
AD8436
ORDERING GUIDE
Model1
Temperature Range
−40°C to +125°C
−40°C to +125°C
−40°C to +125°C
0°C to +70°C
Package Description
Package Option
CP-20-8
CP-20-8
CP-20-8
CP-20-8
CP-20-8
CP-20-8
RQ-20
RQ-20
RQ-20
RQ-20
RQ-20
AD8436ACPZ-R7
AD8436ACPZ-RL
AD8436ACPZ-WP
AD8436JCPZ-R7
AD8436JCPZ-RL
AD8436JCPZ-WP
AD8436ARQZ-R7
AD8436ARQZ-RL
AD8436ARQZ
20-Lead Lead Frame Chip Scale [LFCSP]
20-Lead Lead Frame Chip Scale [LFCSP]
20-Lead Lead Frame Chip Scale [LFCSP]
20-Lead Lead Frame Chip Scale [LFCSP]
20-Lead Lead Frame Chip Scale [LFCSP]
20-Lead Lead Frame Chip Scale [LFCSP]
20-Lead Shrink Small Outline Package [QSOP]
20-Lead Shrink Small Outline Package [QSOP]
20-Lead Shrink Small Outline Package [QSOP]
20-Lead Shrink Small Outline Package [QSOP]
20-Lead Shrink Small Outline Package [QSOP]
20-Lead Shrink Small Outline Package [QSOP]
Evaluation Board
0°C to +70°C
0°C to +70°C
−40°C to +125°C
−40°C to +125°C
−40°C to +125°C
−40°C to +125°C
−40°C to +125°C
−40°C to +125°C
AD8436BRQZ-R7
AD8436BRQZ-RL
AD8436BRQZ
RQ-20
AD8436-EVALZ
1 Z = RoHS Compliant Part.
©2011–2017 Analog Devices, Inc. All rights reserved. Trademarks and
registered trademarks are the property of their respective owners.
D10033-0-3/17(E)
Rev. E | Page 21 of 21
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