AD AM400

UNIVERSAL AMPLIFIER IC
AM400
PRINCIPLE FUNCTION
Amplification and conversion of differential input voltages or
those referenced to ground to industrial standard current (0/4...20mA) or
voltage signals (e.g. 0...5/10V, 0.5...4.5V)
VCC = 6…35V
Differential input
voltage 400mV
IOUT = 0/4...20mA
AM400
Input voltage referenced
to ground 0...VCC-5V
VOUT = 0...VCC- 5V
adjustable, e.g. 0...5/10V
IS = max 10mA
VREF= 5/10V
TYPICAL APPLICATIONS
•
•
•
•
•
Transducer for sensor applications
Analog industrial output stage for microprocessor applications
Modular signal conditioning with digital correction (Frame ASIC [1])
Protected output stage power network
Impedance converter
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Februar 2006
1/21
Rev.: 4.3
UNIVERSAL AMPLIFIER IC
AM400
CONTENTS
FEATURES
3
GENERAL DESCRIPTION
3
BLOCK DIAGRAM
3
ELECTRICAL SPECIFICATIONS
4
BOUNDARY CONDITIONS
7
DETAILED DESCRIPTION OF FUNCTIONS
7
OPERATING AM400
10
General information on 2- and 3-wire applications
10
Setting the voltage gain using the voltage output
11
Setting the output current range and compensating for the offset using the current output
11
Selecting the supply voltage
11
POINTS TO NOTE: INITIAL OPERATION OF AM400
12
APPLICATIONS
13
1) Typical 3-wire application with a differential input signal
13
2) Typical 3-wire application with an input signal referenced to ground
14
3) Typical 2-wire application with a differential input signal
15
4) Application for the 16-pole version of AM400 (3-wire application)
17
BLOCK DIAGRAM, 20-POLE PINOUT AND DICE
18
BLOCK DIAGRAM AND 16-POLE PINOUT
19
EXAMPLE APPLICATIONS
20
DELIVERY
21
PACKAGE DIMENSIONS
21
FURTHER READING
21
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Februar 2006
2/21
Rev.: 4.3
UNIVERSAL AMPLIFIER IC
AM400
FEATURES
GENERAL DESCRIPTION
• Instrumentation amplifier with a wide
input voltage range
• Adjustable gain and offset
• Parallel analog voltage (e.g. 0...5/10V)
and current (e.g. 0/4...20mA) output
• Two and three-wire operation
• Protection against reverse polarity and
short-circuiting
• Output current limitation
• Integrated current source
• Adjustable integrated reference voltage
source: 4.5 to 10V
• Supply voltage: 6...35V
• Wide operating temperature range:
-40°C...+85°C
• Individually accessible function modules
• RoHS compliant
• Two package variants: SOP and SSOP
AM400 is a monolithically integrated measuring
amplifier with a parallel current and voltage
output which has been specifically developed for
the processing of differential input signals.
AM400 consists of various functional modules.
It contains both an instrumentation amplifier
input and an input for signals referenced to
ground. One particular feature of the device is
the current and voltage outputs which can be
used simultaneously. The output ranges can be
selected using external resistors, enabling
AM400 to be configured for the analog
0/4...20mA and 0...5/10V industrial power network, for example. Integrated voltage and
current sources covering a wide range of values
can be used to power external components.
AM400 has been designed for ideal use with
external processors (such as a microprocessor,
for example, for signal correction [1]).
BLOCK DIAGRAM
SET
VSET VREF
20
19
16
CVREF
1
AM400-0
CVSET
I
2
OP3
13
Voltage reference
12
VBG
IN+
14
V
11
3
IA
OP1
4
OP2
15
INZA
7
OUTIA INOP GAIN
17
5
6
8
9
10
OUTAD INDAI INDAV
GND
RS+
VCC
RSIOUT
VOUT
18
Figure 1: Block diagram of AM400 in the 20-pole version
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Februar 2006
3/21
Rev.: 4.3
UNIVERSAL AMPLIFIER IC
AM400
ELECTRICAL SPECIFICATIONS
Tamb = 25°C, VCC = 24V, VREF = 5V, IREF = 1mA (unless otherwise stated); currents flowing into the IC are negative.
Parameter
Symbol
Supply Voltage Range
VCC
Quiescent Current
ICC
Conditions
Min.
Typ.
6
Tamb = – 40...+85°C, IREF = 0mA
Max.
Unit
35
V
1.5
mA
°C
Temperature Specifications
Operating
Tamb
–40
85
Storage
Tst
–55
125
°C
Junction
TJ
150
°C
Voltage Reference
Voltage
VREF
VSET not connected
VREF**
VSET = GND, VCC ≥ 11V
Trim Range
VR10**
Current
IREF*
VREF vs. Temperature
dVREF/dT
Tamb = - 40...+85°C
Line Regulation
dVREF/dV
VCC = 6V...35V
dVREF/dV
VCC = 6V...35V, IREF ≈ 5mA
Load Regulation
5.00
5.25
V
9.5
10.0
10.5
V
4.5
VR10
V
0
10.0
mA
±90
±140
ppm/°C
30
80
ppm/V
60
150
ppm/V
dVREF/dI
dVREF/dI
Load Capacitance
4.75
0.05
0.10
%/mA
0.06
0.15
%/mA
1.9
2.2
5.0
µF
1.20
1.27
1.35
V
±60
±140
ppm/°C
IREF ≈ 5mA
CL
Current/Voltage Source OP3
Internal Reference
VBG
VBG vs. Temperature
dVBG/dT
Tamb = - 40...+85°C
Current Source: ICV = VBG/REXT
Adjustable Current Range
ICV*
0
10
mA
Output Voltage
VCV
VCC < 19V
VBG
VCC – 4
V
VCV
VCC ≥ 19V
VBG
15
V
Voltage Source: VCV = VBG (REXT1 + REXT2) / REXT2
Adjustable Voltage Range
Output Current
Load Capacitance
VCV
VCC < 19V
0.4
VCC – 4
V
VCV
VCC ≥ 19V
0.4
15
V
ICV*
Source
ICV
Sink
CL
Source mode
10
mA
–100
µA
nF
0
1
10
5
5.1
Instrumentation Amplifier
Internal Gain
GIA
4.9
Differential Input Voltage Range
VIN
0
±400
Common Mode Input Range
CMIR
VCC < 9V, ICV < 2mA
1.5
VCC – 3
V
CMIR
VCC ≥ 9V, ICV < 2mA
1.5
6.0
V
Common Mode Rejection Ratio
CMRR
80
90
Power Supply Rejection Ratio
PSRR
80
90
Offset Voltage
VOS
±1.5
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mV
dB
dB
±6
mV
October 2005
4/21
Rev. 4.2
UNIVERSAL AMPLIFIER IC
AM400
Parameter
Symbol
Conditions
Min.
Typ.
Max.
Unit
Instrumentation Amplifier (cont.)
VOS vs. Temperature
dVOS/dT
µV/°C
±5
Input Bias Current
IB
–100
–250
nA
IB vs. Temperature
dIB/dT
–0.4
–0.9
nA/°C
Output Voltage Range
VOUTIA
VCC < 9V, RLIA ≤ 10kΩ
0***
VCC – 4
V
VOUTIA
VCC ≥ 9V, RLIA ≤ 10kΩ
0***
5
V
Minimum Output Voltage
VOUTIAmin
Without external load resistance RLIA
16
mV
Load Capacitance
CL**
250
pF
4.5
Zero Adjust Stage
Internal Gain
GZA
Input Voltage
VZA
0,94
Offset Voltage
VOS
±0.5
VOS vs. Temperature
dVOS/dT
±1.6
Input Bias Current
IB
47
IB vs. Temperature
dIB/dT
18
30
pA/°C
VZA ≤ VOUTIA - GIA VIN
1
0
1,06
VOUTIA
V
±2.0
mV
±5
µV/°C
120
nA
Operational Amplifier Gain Stage (OP1)
Adjustable Gain
GGAIN
Input Range
IR
VCC < 10V
1
0
VCC – 5
V
IR
VCC ≥ 10V
0
5
V
±0.5
±2
mV
±7
µV/°C
Power Supply Rejection Ratio
PSRR
Offset Voltage
VOS
VOS vs. Temperature
dVOS/dT
±3
Input Bias Current
IB
10
25
nA
IB vs. Temperature
dIB/dT
7
20
pA/°C
Output Voltage Limitation
VLIM
Output Voltage Range
VOUTAD
VCC < 10V
0
VCC – 5
V
VOUTAD
VCC ≥ 10V
0
VREF
V
250
pF
Load Capacitance
80
90
dB
VREF
CL
V
Operational Amplifier Output Stage (OP2)
Internal Gain
GOP
Input Range
IR
VCC < 11V
2.15
0
VCC – 5
V
IR
VCC ≥ 11V
0
6
V
±0.5
±2
mV
±7
µV/°C
80
2.20
2.25
Power Supply Rejection Ratio
PSRR
Offset Voltage
VOS
VOS vs. Temperature
dVOS/dT
±3
Input Bias Current
IB
10
25
nA
IB vs. Temperature
dIB/dT
7
20
pA/°C
Output Voltage Range
VOUT
VCC – 5
V
VCC < 19V
0
VOUT
VCC ≥ 19V
0
Output Current Limitation
ILIM
VOUT ≥ 10V
5
Output Current
IOUT
0
Load Resistance
RL
2
Load Capacitance
CL
7
dB
14
V
10
mA
ILIM
mA
kΩ
500
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nF
October 2005
5/21
Rev.: 4.2
UNIVERSAL AMPLIFIER IC
AM400
Parameter
Symbol
Conditions
Min.
Typ.
Max.
0,120
0.125
0,130
0.75
1.00
1.25
Unit
V/I Converter
Internal Gain
GVI
Trim Range
Adjustable by R0
Voltage Range at R0 FS
VR0FS
350
Offset Voltage
VOS
βF ≥ 100
VOS vs. Temperature
dVOS/dT
βF ≥ 100
Input Resistance
RIN
RIN vs. Temperature
dRIN/dT
Output Offset Current
IOUTOS
3-wire operation
–25
–35
µA
IOUTOS vs. Temperature
dIOUTOS/dT
3-wire operation
16
26
nA/°C
Output Offset Current
IOUTOS
2-wire operation
9.5
14
µA
IOUTOS vs. Temperature
dIOUTOS/dT
2-wire operation
6
8
nA/°C
Output Control Current
IOUTC
2-wire operation, VR0/100mV
IOUTC vs. Temperature
dIOUTC/dT
2-wire operation
Output Voltage Range
VOUT
VOUT = RL IOUT, VCC < 18V
0
VCC – 6
V
VOUT
VOUT = RL IOUT, VCC ≥ 18V
0
12
V
Output Current Range FS
IOUTFS
IOUT = VR0/R0, 3-wire operation
Output Resistance
ROUT
Load Capacitance
CL
120
0.2
0.5
750
mV
±2
±4
mV
±7
±14
µV/°C
160
kΩ
0.3
kΩ/°C
6
8
µA
–10
–15
nA/°C
20
mA
1.0
MΩ
0
500
nF
SET Stage
Internal Gain
GSET
0.5
Input Voltage
VSET
1.15
V
Offset Voltage
VOS
±0.5
±1.5
mV
VOS vs. Temperature
dVOS/dT
±1.6
±5
µV/°C
0
Input Bias Current
IB
8
20
nA
IB vs. Temperature
dIB/dT
7
18
pA/°C
Protection Functions
Voltage Limitation at R0
VLIMR0
VR0 = VIN GI, SET = GND
VREF/8
mV
Only if OP2 and V/I-Converter are
connected
VLIMR0
VIN = 0, VR0 = VSET/2
580
635
Protection against reverse polarity
Ground vs. VS vs. VOUT
Current in case of reverse polarity
Ground = 35V, VS = IOUT = 0
4.5
Ideal input
0.05
Ground vs. VS vs. IOUT
690
mV
35
V
35
V
mA
System Parameters
Nonlinearity
0.15
%FS
* In 2-wire operation a maximum current of IOUTmin – ICC is valid
** Only available in die form or in an SSOP 20 version
*** Depending on external load resistance at output IA (RLIA ≤ 10kΩ ⇒ VOUTIA < 3mV); internal load resistance is ≈ 100kΩ
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October 2005
6/21
Rev.: 4.2
UNIVERSAL AMPLIFIER IC
AM400
BOUNDARY CONDITIONS
Parameter
Symbol
Sense Resistor
Conditions
R0
IOUTFS = 20mA
R0
c = 20mA/IOUTFS
Stabilization Resistor
R5
IOUTFS = 20mA
R5
c = 20mA/IOUTFS
Load Resistance
RL
Limitation only for 3-wire operation
Min.
Typ.
Max.
17
27
38
Unit
Ω
c ⋅ 17
c ⋅ 27
c ⋅ 38
Ω
35
40
45
Ω
c ⋅ 35
c ⋅ 40
c ⋅ 45
Ω
0
600
Ω
Sum Gain Resistors
R1 + R2
20
200
kΩ
Sum Offset Resistors
R3 + R4
20
200
kΩ
VREF Capacitance
C1
Min. value for Tamb 85°C
1.9
2.2
5.0
µF
Output Capacitance
C2
Only for 2-wire operation
90
100
250
nF
D1 Breakdown Voltage
VBR
35
50
T1 Forward Current Gain
βF
50
150
BCX54/55/56, for example
V
DETAILED DESCRIPTION OF FUNCTIONS
AM462 is a modular, monolithically integrated universal amplifier which has been specifically
developed for the conditioning of differential voltage signals and those referenced to ground. It is
designed for both 2- and 3-wire operation1 in industrial applications (cf. applications on pages 14
until 19). AM462’s various functions are depicted in the block diagram (Figure 1) which also
illustrates how few external components are required for the operation of this particular device.
AM400 consists of a number of modular functional blocks which through external gating can either
operate together or separately (see Figure 2).
1. The instrumentation amplifier (IA) with an internal gain of GIA = 5 acts as an input stage for
differential voltage signals. Its special construction permits a high common mode rejection ratio
(CMRR). The amplifier reference potential is set externally using the AM400 pin ZA. Output
voltage VOUTIA at pin OUTIA is calculated for VZA > 0 as:
VOUTIA = GIA VIN + VZA with VOUTIA > 0
(1)
where VIN is the differential voltage between inputs pin IN+ and pin IN- of the IA and VZA is the
voltage at pin ZA.
2. The ensuing operational amplifier stage (OP1) permits the IA output signal to be amplified
further. OP1’s gain of GGAIN can be set using external resistors R1 and R2. Protection against
overvoltage has been integrated into the device; this protective circuitry limits the voltage to the
set reference voltage value (cf. paragraph 5 in this section).
1
The principle of design is such that only the current output can be used in 2-wire operation.
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7/21
Rev.: 4.2
UNIVERSAL AMPLIFIER IC
AM400
Output voltage VOUTAD at pin OUTAD is calculated as:
R

VOUTAD = VINOP ⋅ GGAIN with GGAIN =  1 + 1
 R2

(2)
where VINOP is the voltage at the OP1 input pin INOP. Alternatively, the OP1 input pin INOP can
also be used as an input for signals referenced to ground (see Application 2, Figure 6).
VREF
VCVREF
1
AM400-0
VCVSET
R3
C1
20
19
16
R4
VS
VSET
I
2
OP3
VIN-
R0
13
Voltage reference
12
VBG
VIN+
14
V
11
3
T1
D1
IA
OP1
4
17
5
6
8
7
VZA
VOUTIAVINOP
OP2
R2
R1
VOUTAD
9
10
15
18
R5
VOUT
IOUT
VINDAI VINDAV
Ground
Figure 2: Block diagram of AM400 showing external components (3-wire circuit
with a current output)
3. The IC’s voltage output VOUT is realized via the current-limited operational amplifier stage
(OP2) which has integrated protection against reverse polarity. The internal gain of OP2 is set to
a fixed value of GOP = 2.2. The output is engineered as a driver stage. The following applies to
OP2’s output voltage VOUT at the IC pin VOUT:
VOUT = GOP ⋅ VINDAV
(3)
where VINDAV is the voltage at pin INDAV (OP2 input).
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Rev.: 4.2
UNIVERSAL AMPLIFIER IC
AM400
4. The voltage-to-current converter (V/I converter) provides a voltage-controlled current signal at
IC output IOUT which activates an external transistor T1; this reduces the power dissipation of
the IC and supplies the output current IOUT. The external transistor is protected against reverse
polarity by an additional diode D1. Via pin SET an offset current ISET can be set at output IOUT
(with the help of the internal voltage reference and an external voltage divider as shown in
Figure 5, for example). External resistor R0 permits the output current to be finely adjusted with
parallel operation of current and the voltage output. For the output current IOUT boosted by T1
the following ratio applies:
I OUT =
VINDAI
V
+ I SET with I SET = SET
8 R0
2R 0
(4)
with VINDAI the voltage at pin INDAI and VSET the voltage at pin SET (V/I converter inputs, see
Figure1)2.
5. The AM400 reference voltage source enables voltage to be supplied to external components
(such as sensors, microprocessors, etc.). The reference voltage value VREF can be set via pin
VSET. If pin VSET is not connected, VREF = 5V; if VSET is switched to ground, VREF = 10V.
Values between the above can be set if two external resistors are used (inserted between pin
VREF and pin VSET and between pin VSET and GND).
External capacitor C1 stabilizes the reference voltage. It must be connected even if the voltage
reference is not in use. It also must not exceed the minimum value.
6. The additional operational amplifier (OP3) can be used as a current or voltage source for the
supply of external components. OP3’s positive input is connected internally to voltage VBG so
that the output current or voltage can be set across a wide range using one or two external
resistors.
2
The construction of the V/I converter is such that output current IOUT is largely independent of the current
amplification βF of external transistor T1. Production-specific variations in the current amplification of the transistors
used are compensated for internally by the V/I converter.
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October 2005
9/21
Rev.: 4.2
UNIVERSAL AMPLIFIER IC
AM400
OPERATING AM400
General information on 2- and 3-wire applications
In 3-wire operation (cf. Figure 5, for example) the ground of the IC (pin GND) is connected up to
the external mass of the system Ground. The system's supply voltage VS is connected to pin VCC
and pin VCC to pin RS+.
In 2-wire operation (cf. Figure 7) system supply voltage VS is connected to pin RS+ and pin VCC to
RS-. The ground of the IC (pin GND) is connected to the node between resistor R5 and load resistor
RL (current output IOUT). IC ground (GND) is not the same as system ground (Ground)!! The output
signal is picked up via load resistor RL which connects current output IOUT to the system ground.
In 2-wire operation the IC ground is "virtual" (floating), as with a constant load resistance the
supply voltage of the device VCC changes according to the current. As a rule, the following equation
applies to 2-wire operation:
VCC = VS − I OUT (VIN ) RL
(5)
The reason for this is that in 2-wire operation the IC is connected in series to the actual load resistor
RL. This is illustrated in Figure 3.
In 3-wire operation Equation 5 no longer applies as the IC ground is connected to the ground of the
system. For 3-wire operation the supply voltage can be expressed thus:
VCC = VS
(6)
In a 2-wire setup the power consumption of the overall system (AM400 and all external
components including the adjusting resistors) may not exceed IOUTmin (usually 4mA).
2-wire system
Signal source and
conditioning IC
GND ≠ Ground
VCC ≠ VS
3-wire system
Signal source and
conditioning IC
VCC
IOUT
GND
RL
VS
GND = Ground
VCC = VS
Ground
IOUT
VCC = VS
RL
Ground = GND
Figure 3: The difference between 2- and 3-wire operation
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October 2005
10/21
Rev.: 4.2
UNIVERSAL AMPLIFIER IC
AM400
Setting the voltage gain using the voltage output
When using the IA and amplifier stages OP1 and OP2 for further signal conditioning the overall
gain can be set using the suitably selected external resistors R1 and R2. The transfer function for the
output voltage is calculated by multiplying Equations 1, 2 and 3 to:
VOUT = (GIAVIN + VZA ) ⋅ GGAIN ⋅ GOP
(7)
with GIA = 5, GGAIN = (R1 /R2) + 1 and GOP = 2.2 and the externally set voltage VZA at pin ZA.
Setting the output current range and compensating for the offset using the current output
When using the IA together with amplifier stage OP1 and the V/I converter for further signal
conditioning the offset of the output current should first be compensated for. To this end the two IA
inputs must be short-circuited (VIN = 0) and connected up to a permitted potential (cf. CMIR in the
electrical specifications on page 5). With the short circuit at the input the values of the output
current according to Equation 4 and an external voltage divider (e.g. Figure 5) are as follows:
I OUT (V IN = 0 ) = I SET with I SET =
VREF
R4
⋅
2R0 R3 + R4
(8)
The output current range is set in conjunction with the selected external resistors R1 and R2 (or fine
adjustment with R0 ). Using Equations 2, 4 and 8 the following is calculated for output current IOUT :
I OUT = VIN
GI
+ I SET with GI = GIA ⋅ GGAIN and VZA = 0
8R0
(9)
Selecting the supply voltage
System supply voltage VS needed to operate AM400 is dependent on the selected mode of
operation.
•
When using voltage output pin VOUT the minimum supply voltage VS necessary for the
operation of the device depends on the maximum output voltage VOUTmax required by the
application. The following applies:
VS ≥ VOUT max + 5V
•
(10)
When using current output pin IOUT (in conjunction with the external transistor) the value of VS
is dependent on that of the relevant load resistor RL (max. 600Ω) used by the application. The
minimum system supply voltage VS is then:
VS ≥ I OUT max RL + VCC min
(11)
analog microelectronics
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October 2005
11/21
Rev.: 4.2
UNIVERSAL AMPLIFIER IC
AM400
Here, IOUTmax stands for the maximum output current and VCCmin for the minimum IC supply
voltage which is dependent on the selected reference voltage:
VCC min ≥ VREF + 1V
(12)
The working range resulting from Equation 11 is described in Figure 4. Example calculations and
typical values for the external components can be found in the example applications.
POINTS TO NOTE: INITIAL OPERATION OF AM400
1. When operating AM400 it is imperative that external capacitance C1 (a high-grade ceramic
capacitor) is always connected (cf. Figure 2). Care must be taken that the value of the
capacitance does not lie beyond its given range, even across the range of temperature (see
Boundary Conditions on page 7). In 2-wire operation ceramic capacitor C2 must also be used.
RL [Ω]
RL ≤
VCCmin = 6V
VS − VCCmin
IOUTmax
RLmax = 600Ω
IOUTmax = 20mA
600
300
Working range
0
0
6
12
18
24
35
VS [V]
Figure 4: Working range in conjunction with the load resistor
2. All of the AM400 function blocks not used by the application (e.g. OP3) must be connected up
to a defined (and permitted) potential.
3. The voltages at the IA inputs (pins IN+ and IN–) must always lie within input voltage range
CMIR, even if the IA is not used.
4. When the voltage output is in operation the load resistance at pin VOUT must be at least 2kΩ.
5. A load resistance of 600Ω maximum is permitted with operation of the current output.
6. The values of external resistors R0, R1, R2, R3, R4 and R5 must be selected within the permissible
range given in the boundary conditions on page 7.
analog microelectronics
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October 2005
12/21
Rev.: 4.2
UNIVERSAL AMPLIFIER IC
AM400
APPLICATIONS
1) Typical 3-wire application with a differential input signal
In 3-wire operation (cf. Figure 5, for example) the IC ground (pin GND) is connected up to the
external ground of the system (Ground). The system’s supply voltage VS is connected to pin VCC
and pin VCC to pin RS+.
C1
1
AM400-0
R3
VS
20
19
16
3-wire connection
R4
I
2
OP3
R0
13
Voltage reference
12
VBG
RSET
14
V
11
3
D1
IA
OP1
4
17
T1
5
6
RIAL
Negative offset voltages can be
compensated for using pin ZA.
If the pin is not in use it must be
connected to IC ground GND.
OP2
8
7
R2
9
10
R1
15
18
R5
VOUT
IOUT
RL
Ground
Load resistor to minimize the offset
voltage at the IA output.
Figure 5: Typical 3-wire application for differential input
Figure 5 shows a 3-wire application in which the differential output signal of a current-powered
measuring bridge is amplified and converted. Operational amplifier OP3 supplies the measuring
bridge with current. Bridge supply current IS can be set using resistor RSET:
IS =
V BG
1 .27 V
=
R SET
R SET
(13)
For the above application it is assumed that no negative input voltages are present. Pin ZA is first
connected to the IC’s ground GND. According to Equation 3 the following then applies to output
voltage VOUT:
 R 
VOUT = GV VIN with GV = GIA GGAIN GOP = 5 1 + 1  2.2
(14)
 R2 
analog microelectronics
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October 2005
13/21
Rev.: 4.2
UNIVERSAL AMPLIFIER IC
AM400
According to Equation 4 the following is then relevant to output current IOUT:
I OUT = VIN
GI
+ I SET with VZA = 0
8R0
(15)
V
R4

R 
.
with GI = GIA GGAIN = 5 1 + 1  and I SET = REF ⋅
R2 
2 R0 R3 + R 4

Example 1: VIN = 0...100mV (differential), IOUT = 4...20mA and VOUT = 0...10V
For a measuring bridge with a signal of VIN = 0...100mV at the IA input the external components are
to be dimensioned in such a way that the output current has a range of 4...20mA and the output
voltage one of 0...10V.
R1 and R2 are dimensioned in accordance with Equation 14, R0 according to Equation 4 and R3 and
R4 according to Equation 8. Observing the boundary conditions for the external components the
following values are then obtained:
R0 ≈ 35.5Ω
R5 = 39Ω
R1 ≈ 80.9kΩ
RL = 0...600Ω
R2 = 10kΩ
RIAL ≤ 10kΩ
R3 = 83kΩ
C1 = 2.2µF
R4 = 5kΩ
2) Typical 3-wire application with an input signal referenced to ground
C1
1
AM400-0
R3
I
2
OP3
VS
20
19
16
3-wire connection
R4
14
R0
13
Voltage reference
12
VBG
V
11
3
D1
IA
OP1
4
17
5
6
OP2
8
7
VIN
Input voltage
referenced to ground
T1
R2
9
10
R1
15
18
R5
VOUT
IOUT
RL
Connections setting unused function blocks to a defined operating point
Ground
Figure 6: Typical application for input signals referenced to ground
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October 2005
14/21
Rev.: 4.2
UNIVERSAL AMPLIFIER IC
AM400
Figure 6 shows a 3-wire application in which AM400 amplifies and converts a voltage signal
referenced to ground. The blocks unused by the application (IA and OP3) are set to a defined
operating point. Alternatively, these function blocks can also be used for the supply of external
components, for example.
In the above application output voltage VOUT is calculated using Equations 2 and 3 as:

R 
VOUT = GV VIN with GV = GGAIN GOP = 1 + 1  2.2
 R2 
According to Equation 4 the following applies to output current IOUT:
I OUT = VIN
GI
+ I SET
8R0
V
R4

R 
with GI = GGAIN = 1 + 1  and I SET = REF ⋅
2 R0 R3 + R 4
 R2 
Example 2: VIN =0…1V (referenced to ground), IOUT = 4...20mA and VOUT = 0...10V
For a signal of VIN = 0...1V at the OP1 input the external components are to be dimensioned in such
a way that the output current has a range of 4...20mA and the output voltage one of 0...10V.
Observing the boundary conditions the following values are obtained for the external components:
R0 ≈ 35.5Ω
R5 = 39Ω
R1 ≈ 35.5kΩ
RL = 0...600Ω
R2 = 10kΩ
C1 = 2.2µF
R3 = 83kΩ
R4 = 5kΩ
3) Typical 2-wire application with a differential input signal
In 2-wire operation (cf. Figure 7) system supply voltage VS is connected up to pin RS+ and pin VCC
to pin RS-. The ground of the IC (pin GND) is connected to the node between resistor R5 and load
resistor RL (current output IOUT). IC ground (GND) is not the same as system ground (Ground)!!
The output signal is picked up via load resistor RL which connects current output IOUT to the system
ground.
Figure 7 shows a typical 2-wire application in which the differential output signal of a currentpowered measuring bridge is amplified by the IA and OP1 and converted by the V/I converter.
Operational amplifier OP3 supplies the measuring bridge with current. Bridge supply current IS can
be set using resistor RSET according to Equation 13.
According to Equation 4 the following applies to the output current of the 2-wire application:
I OUT = VIN
GI
+ I SET with VZA = 0 ( ZA connected to GND )
8R0
analog microelectronics
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October 2005
15/21
Rev.: 4.2
UNIVERSAL AMPLIFIER IC
AM400

R 
V
R4
where GI = GIA GGAIN = 5 1 + 1  and I SET = REF ⋅
R
2
R
R
2
0
3 + R4

C1
1
AM400-0
R3
VS
20
19
16
R4
C2
I
2
OP3
R0
13
Voltage reference
12
VBG
RSET
14
V
11
3
D1
IA
OP1
4
17
T1
5
6
RIAL
OP2
8
7
R2
9
10
2-wire
connection
15
18
R5
IOUT
R1
RL
GND
Negative offset voltages can be
compensated for using pin ZA.
If the pin is not in use it must be
connected to IC ground GND.
IC ground: GND
}
System ground: Ground
Ground
Different potentials!
Figure 7: Typical 2-wire application for differential input signals
Example 3: VIN = 0..100mV (differential) and IOUT = 4...20mA
For a measuring bridge with a signal of VIN = 0...100mV at the IA input the external components of
the AM400 circuitry are to be dimensioned in such a way that the output current has a range of
4...20mA.
As only the current output is to be used, the gain and output current range can be dimensioned using
resistors R1 to R4. Up to a certain point the value of resistor R0 is freely selectable and can be set to
27Ω. Observing the boundary conditions for the external components the following values are then
obtained:
R0 = 27Ω
R5 = 39Ω
R1 ≈ 59.12kΩ
RL = 0...600Ω
R2 = 10kΩ
RIAL ≤ 10kΩ
R3 = 82kΩ
C1 = 2.2µF
R4 = 5kΩ
C2 = 100nF
In this specific application particular attention must be paid to the current consumption which at a
temperature of 85°C may not exceed 4mA.
analog microelectronics
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October 2005
16/21
Rev.: 4.2
UNIVERSAL AMPLIFIER IC
AM400
4) Application for the 16-pole version of AM400 (3-wire application)
Figure 8 gives a 3-wire application which uses the 16-pole version of AM400 (Figure 11). The
dimensions of this specific application are no different from those of the 3-wire setup illustrated in
Figure 5; no detailed description shall thus be given here. One difference, however, lies in the fact
that the minimum voltage at the IA output cannot be reduced by connecting up external load resistor
RLIA. Particularly with small differential input signs and the large GOP gain these entail a “correct”
value of 0V cannot be obtained at IC output VOUT (cf. the comments on VOUTIA in the electrical
specifications). For this reason the 20-pole version of AM400 is preferable for small signals.
C1
AM400-1
1
R3
3-wire connection
R4
16
15
I
2
OP3
RSET
VS
11
R0
10
5V Reference
9
VBG
V
3
IA
The minimum voltage
at the IA output is 16mA
T1
D1
OP1
4
13
8
VOUTIA
6
5
R2
12
OP2
7
R1
14
R5
VOUT
IOUT
RL
Ground
Figure 8: Typical application for the 16-pole version of AM400 (3-wire)
analog microelectronics
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October 2005
17/21
Rev.: 4.2
UNIVERSAL AMPLIFIER IC
AM400
BLOCK DIAGRAM, 20-POLE PINOUT AND DICE
SET
VSET VREF
20
19
16
CVREF
1
AM400-0
CVSET
OP3
13
Voltage reference
12
VBG
IN+
14
I
2
V
11
3
IA
OP1
4
OP2
15
INZA
7
OUTIA INOP GAIN
17
5
8
6
9
10
GND
OUTAD INDAI INDAV
RS+
VCC
RSIOUT
VOUT
18
Figure 9: Block diagram of AM400 in the 20-pole version
PIN
NAME
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
CVREF
CVSET
IN+
IN–
OUTIA
INOP
GAIN
OUTAD
INDAI
INDAV
IOUT
RS–
VCC
RS+
VOUT
VSET
ZA
GND
VREF
SET
EXPLANATION
Current/Voltage reference
Current/Voltage reference set
Positive input IA
Negative input IA
Output IA
Positive amplification OP input
Gain set
System gain output
Current output stage input
Voltage output stage input
Current output
Sensor resistor –
Supply voltage
Sensor resistor +
Voltage output
Set reference voltage source
Zero adjustment (offset)
IC ground
Reference voltage source output
Output offset current set
CVREF
CVSET
IN+
INOUTIA
INOP
GAIN
OUTAD
INDAI
INDAV
1
2
3
4
5
6
7
8
9
10
20
19
18
17
16
15
14
13
12
11
SET
VREF
GND
ZA
VSET
VOUT
RS+
VCC
RSIOUT
Figure 10: Pinout of the 20-pole version
of AM400
Table 1: Pinout of the 20-pole version of AM400
analog microelectronics
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October 2005
18/21
Rev.: 4.2
UNIVERSAL AMPLIFIER IC
AM400
BLOCK DIAGRAM AND 16-POLE PINOUT
VREF
CVREF
AM400-1
CVSET
1
SET
16
15
11
I
2
OP3
10
5V Reference
9
VBG
V
IN+
8
3
IA
OP1
4
12
OP2
INZA
13
GAIN
5
OUTAD
6
7
INDA
GND
RS+
VCC
RSIOUT
VOUT
14
Figure 11: Block diagram of AM400 in the 16-pole version
PIN
NAME
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
CVREF
CVSET
IN+
IN–
GAIN
OUTAD
INDA
IOUT
RS–
VCC
RS+
VOUT
ZA
GND
VREF
SET
EXPLANATION
Current/Voltage reference
Current/Voltage reference set
Positive input IA
Negative input IA
Gain set
System gain output
Output stage input
Current output
Sensor resistor –
Supply voltage
Sensor resistor +
Voltage output
Zero adjustment (offset)
IC ground
Reference voltage source output
Output offset current set
CVREF
CVSET
IN+
INGAIN
OUTAD
INDA
IOUT
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
SET
VREF
GND
ZA
VOUT
RS+
VCC
RS-
Figure 12: Pinout of the 16-pole
version of AM400
Table 2: Pinout of the 16-pole version of AM400
analog microelectronics
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October 2005
19/21
Rev.: 4.2
UNIVERSAL AMPLIFIER IC
AM400
EXAMPLE APPLICATIONS
•
Signal conditioning for ceramic and piezoresistive pressure sensing elements with an optional
external processor for error compensation
VS = 6...35V
Sensor supply
Voltage or current
0/4...20mA
AM400
0...5/10V
µP
Figure 13: Application for ceramic and piezoresistive pressure sensors and an external
microcontroller
•
Application as a converter IC
5V
CX1
6...35V
0/4...20mA
AM400
CAV424
CX2
0...5/10V
Figure 14: Application as a converter IC together with CAV424 for the measurement of capacitive
V424 signals
•
Conditioning of signals referenced to ground (protected output stage, impedance converter, etc.)
6...35V
VIN = 0...1, 0...5V
Others
AM400
Protection against
short-circuiting and
reverse polarity
0/4...20mA
Figure 15: Application for input signals referenced to ground (protected output stage,
impedance converter, etc.)
analog microelectronics
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October 2005
20/21
Rev.: 4.2
UNIVERSAL AMPLIFIER IC
AM400
DELIVERY
The AM400 sensor transmitter is available as the following packages:
• SSOP20
• SO16(n)
• Dice on 5" blue foil (on request)
PACKAGE DIMENSIONS
Please see our website (data sheets: package.pdf).
FURTHER READING
[1]
The Frame ASIC concept: http://www.Frame-ASIC.de/
[2]
The Analog Microelectronics GmbH website: http://www.analogmicro.de/
Analog Microelectronics reserves the right to make amendments to any dimensions, technical data or other information contained herein without further notice.
analog microelectronics
Analog Microelectronics GmbH
An der Fahrt 13, D – 55124 Mainz
Internet: http://www.analogmicro.de
Phone:
Fax:
Email:
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October 2005
21/21
Rev.: 4.2