AME AM417

RATIOMETRIC VOLTAGE TRANSMITTER
AM417
FEATURES
GENERAL DESCRIPTION
• Supply Voltage 5V±
±5% (Ratio Range)
• Wide Operating Temperature Range:
–40°C...+100°C
• Ratiometrical Current Source for
Transducer Excitation
• Instrumentation Amplifier Input
• Voltage Output Driver
Open Collector:
VOUT = 0.5–4.5V
IOUT = +10mA
• Adjustable Gain, Offset, and Output
Voltage Range
• Small Package Dimensions: SO8
• Low Cost
The AM417 is a low cost ratiometrical voltage
transmitter, designed for flexible bridge input
signal conditioning. The IC contains a ratiometric current source for transducer excitation, a high accuracy instrumentation amplifier
for differential input signals, and a voltage output driver. Gain, offset, and output voltage
range are adjustable by external resistors. The
voltage output stage is designed as an open collector stage. The output current is +10mA. A
simple current limitation is possible by adding
an external resistor. With its functional blocks
and possibilities to adjust all important parameters for sensor calibration, the small package dimensions (SO8), and the low costs the
AM417 is ideally suited for automotive sensor
interface applications.
APPLICATIONS
• Industrial Process Control
• Automotive Applications
• Sensor Transmitter
DELIVERY
• DIL8 packages (samples)
• SOP8 packages
• Dice on 5“ blue foil
BLOCK DIAGRAM
AM417
IB
IN+
IN−
9R
VCC
IBR
2
OP
VCC
8
1R
4
IA
Output
Stage
5
RB
7
3
6
VOUT
VR
1
GND
Figure 1
analog microelectronics
Analog Microelectronics GmbH
An der Fahrt 13, D – 55124 Mainz
Internet: www.analogmicro.de
Phone: +49 (0)6131/91 073 – 0
Fax:
+49 (0)6131/91 073 – 30
E–Mail: [email protected]
April 99
1/6
Rev. 2.1
RATIOMETRIC VOLTAGE TRANSMITTER
AM417
ELECTRICAL SPECIFICATIONS
Tamb = 25°C, VCC = 5V (unless otherwise noted)
Parameter
Symbol
Voltage Range (Ratio Range)
VCC
Maximum Supply Voltage
VCCmax
Quiescent Current
ICC
Conditions
Min.
Typ.
Max.
Unit
4.75
5
5.25
V
RRB = 500Ω, IIB = 1mA
6
V
6.2
mA
°C
Temperature Specifications
Operating
Tamb
–40
100
Storage
Tst
–55
125
°C
Junction
TJ
150
°C
Thermal Resistance
Θja
DIL8 plastic package
110
°C/W
Θja
SO8 plastic package
180
°C/W
ratiometric with VCC, VVCC = 5V
0.5
V
Ratiometric Current Source – Transducer
Internal Sense Voltage
VRB
Output Current Range
IIB
Output Current
IIB
ratiometric with VCC,
RRB = 500Ω, VVCC = 5V
Ratiometric Error
[email protected]
IRB vs. Temperature
0.50
1.25
mA
1.02
mA
VVCC = 5.25V,
[email protected] = 1.05 VRB (VVCC = 5V)
– VRB (VVCC = 5.25V)
±1
mV
dIRB/dT
IIB = 1mA
±20
ppm/°C
Output Voltage Range
VIB
IIB = 1.25mA
1.5
Output Resistance
RIB
IIB = 1mA, RIB = ∆UIB/∆IIB,
VVIB = 5V, IIB = 1mA
1.5
4.5
MΩ
Power Supply Rejection Ratio
∆IIB
∆VCC = 4.75V – 5.25V,
VVIB = 5V, IIB = 1mA
76
90
dB
0.98
1
VCC–0.5
V
Instrumentation Amplifier
Input Voltage Range
VIN+;–
Internal Gain
GIA
1.5
Common Mode Rejection Ratio
Power Supply Rejection Ratio
Offset Voltage
VOS
±3
mV
VOS vs. Temperature
dVOS/dT
±10
µV/°C
Input Bias Current
IB
Output Voltage Range
VVIA
Output Resistance
ROUT
VIN– = 2V, ∆VIN = 200mV
GIA = ∆VVIA/∆VIN
VCC–2
V
9.8
10.0
CMRR
80
90
dB
PSRR
74
80
dB
VIN = 2V
25
0
75
nA
VCC–2
V
0.1
% FS
20
∆VIN = 200mV, ideal input
Nonlinearity
10.2
kΩ
Voltage Output Stage
Adjustable Gain
GOUT
2
Input Voltage Range
VVR
Power Supply Rejection Ratio
PSSR
Offset Voltage
VOS
VOS vs. Temperature
dVOS/dT
∆VIN = 50mV
Input Current
IIN
∆VIN = 50mV
Output Voltage Range
VOUT
with transistor BCW68H
IOUT = 10mA (see figure 5)
11
0
–72
analog microelectronics
VCC–2.5
–90
20
0.5
V
dB
±3.0
mV
±15
µV/°C
75
nA
4.5
V
April 99
2/6
RATIOMETRIC VOLTAGE TRANSMITTER
Parameter
Symbol
Conditions
Min.
Typ.
AM417
Max.
Unit
Voltage Output Stage (cont.)
Output Current
IOUT
with transistor BCW68H
12.5
mA
Output Current Pin VOUT
IVOUT
pin VOUT
100
200
300
µA
Current Limitation Threshold
VTHRESH
VTHRESH = VVCC – VVOUTmin,
R2 = 27Ω, IOUT ≈ 14mA
120
150
180
mV
VTHRESH vs. Temperature
dVTHRESH /dT
–40...+100°C
1.00
1.15
mV
Output Resistance
ROUT
virtual
Linearity
0.1
ideal input
0.85
Ω
0.01
%FS
Max.
Unit
1000
Ω
2.0
kΩ
BOUNDARY CONDITIONS
Parameter
Symbol
Resistor Adjustment Current Source (Transducer)
Conditions
R1
Min.
400
R3 + R4
Gain Resistor Sum
Typ.
Capacitor Power Supply
C1
100
Capacitor Frequency Compensation (Output Stage)
C2
4.3
5.8
nF
Capacitor Load (Output Stage)
C3
1.0
10.0
nF
Resistor Sense Current Limitation
R2
0
50
Ω
nF
FUNCTIONAL DIAGRAM
VS
IBR
(ratriometrical)
GAIN = 20...110
AMP
VOUT
Ground
Figure 2
analog microelectronics
April 99
3/6
RATIOMETRIC VOLTAGE TRANSMITTER
AM417
FUNCTIONAL DESCRIPTION
The AM417 is an integrated low cost ratiometric voltage transmitter specially designed for bridge
input signals in automotive applications. With its integrated, ratiometrical current source the
AM417 is ideally suited for the signal conditioning of piezoresistive pressure transducers and allows
an easy temperature compensation and span adjustment of a these kinds of sensors.
The AM417 consists of 3 basic functional blocks:
1. A Ratiometrical Current Source for transducer excitation:
The current IIB can be adjusted by the variation of the resistor R1 by the following relation:
I IB =
VVCC
10 R1
2. An Instrumentation Amplifier Input Stage with a fixed gain GIA = 10 for pre–amplifiing the
bridge input signal.
3. An Open Collector Output Stage with the following functions:
• Voltage Output: As output is used a voltage amplifier which has an external PNP–open collector stage T1 which is able to push a maximum current of IOUT = 5mA. The gain GOUT is adjustable by the external resistors R3 and R4 between GOUT = 2...11:
GOUT =
R3
R3 + R4
The gain G of the complete system becomes then G = GIA GOUT.
• Current Limitation: A simple clamp stage for the output pin VOUT limits the voltage drop
against VCC to
VOUT max = VVCC − 15
. VBE (T1 ) .
The maximum current can be set by adding a resistor in series to the Emitter of the transistor T1
at the output stage (see figure 4). For the maximum output current is valid:
I OUT max =
VTRESH − VBE (T1 ) 370mV
≈
.
R2
R2
If no current limitation is required, the Emitter of the transistor T1 has to be directly connected to
VCC (R2 = 0Ω). A proper thermic coupling of the Transistor T1 (VBE–Drift: –2mV/°C typ.)
and the AM417 reduces the resulting temperature drift of IOUT and increases the performance
of the current limitation.
Adjustment of Output Voltage Range
The span of the output voltage could be adjusted by the gain GOUT of the output stage. The offset of
the output voltage can be adjusted in the same way as the adjustment of the sensor offset using the
resistors RO1 and RO2 (figure 4).
analog microelectronics
April 99
4/6
RATIOMETRIC VOLTAGE TRANSMITTER
AM417
PINOUT
PIN
GND
1
8
VCC
IB
2
7
VOUT
RB
3
6
VR
IN+
4
5
IN−
Figure 3
NAME
DESIGNATION
1
GND
IC Ground
2
IB
Output Current Source
3
RB
Adjustment Current Source
4
IN+
Input Positive
5
IN–
Input Negative
6
VR
Adjustment Gain Output Stage
7
VOUT
Out Output Stage
8
VCC
Supply Voltage
DELIVERY
The AM417 is available in:
• 8 pin DIL packages (samples)
• SO 8 packages
• Dice on 5“ blue foil
PACKAGE DIMENSIONS SOP8
4,98 ± 0,1
4,0 + 0,2 - 0,1
1,45 ± 0,1
≤ 2,00
0,2 ± 0,05
0,2 ± 0,1
≤ 0,635
1,27
0,42 ± 0,07
≥ 0,3
0°-10°
6,2 ± 0,2
8
1
4
Figure 4
analog microelectronics
April 99
5/6
RATIOMETRIC VOLTAGE TRANSMITTER
AM417
APPLICATION FOR OUTPUT VOLTAGE 0.5...4.5V
AM417
RTCO1
2
RTCO2
RS RS
RS RS
9R
IBR
OP
VS
8
1R
Output
Stage
4
VIN
VCC
IA
C1
T1
7
VOUT
C2
5
RO2
R2
R3
RO1
C3
RTCS
3
6
1
R1
R4
Ground
Figure 5
The current application shows the basic functions of the AM417. With the given values of the external components (see List of External Components) the following application features are adjusted:
• VIN = 100mV
• G = GIA GOUT = 40
• VOUT = 0.5 – 4.5V
• IOUT = +10mA – 0.25mA
• IBR = 1mA (ratiometrical supply current for the pressure transducer)
LIST OF EXTERNAL COMPONENTS
Symbol
Description
T1
BCW68H, BC557C (or similar)
R1
IBR = 1 mA
R2
IOUT = 10mA min (100°C)
R3
R4
RS
RTCS
RO1, RO2
RTCO1, RTCO2
Value
Unit
low drop, high β at10mA
PNP
500
Ω
15
Ω
Span (Gain adjustment)
500
Ω
VOUT = R3 / (R3 + R4) G
1.5
kΩ
typical transducer resistor
3.0 (typ.)
kΩ
TC span compensation
10 – 120
kΩ
Offset adjustment
0 – 500
Ω
0.1 – 10.0
MΩ
330
nF
}
TC offset adjustment
C1
C2
± 10%
4.7
nF
C3
± 10%
1.0
nF
The information provided herein is believed to be reliable; however, Analog Microelectronics assumes no responsibility for inaccuracies or omissions. Analog Microelectronics assumes no responsibility
for the use of this information, and all use of such information shall be entirely at the user's own risk. Prices and specifications are subject to change without notice. No patent rights or licences to any of
the circuits described herein are implied or granted to any third party. Analog Microelectronics does not authorise or warrant any Analog Microelectronics product use in life support devices and/or
systems.
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April 99
6/6