AM417 AME [Analog Microelectronics], AM417 Datasheet - Page 4

• Manufacturer Part Number: AM417
• Description: RATIOMETRIC VOLTAGE TRANSMITTER
• Manufacturer: AME [Analog Microelectronics]

RATIOMETRIC VOLTAGE TRANSMITTER
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 I
2. An Instrumentation Amplifier Input Stage with a fixed gain G
3. An Open Collector Output Stage with the following functions:
Adjustment of Output Voltage Range
The span of the output voltage could be adjusted by the gain G
the output voltage can be adjusted in the same way as the adjustment of the sensor offset using the
resistors R
analog microelectronics
bridge input signal.
• Voltage Output: As output is used a voltage amplifier which has an external PNP–open col-
The gain G of the complete system becomes then G = G
• Current Limitation: A simple clamp stage for the output pin VOUT limits the voltage drop
The maximum current can be set by adding a resistor in series to the Emitter of the transistor T
If no current limitation is required, the Emitter of the transistor T
lector stage T
justable by the external resistors R
against VCC to
at the output stage (see figure 4). For the maximum output current is valid:
VCC (R
and the AM417 reduces the resulting temperature drift of I
of the current limitation.
O1
IB
and R
2
can be adjusted by the variation of the resistor R
= 0Ω). A proper thermic coupling of the Transistor T
O2
1
which is able to push a maximum current of I
(figure 4).
V
G
I
I
OUT
IB
OUT
OUT
=
max
max
10
V
=
VCC
R
R
=
=
3
1
V
V
R
+
VCC
TRESH
3
R
4
− 15
3
R
−
.
and R
2
V
V
BE
BE
( )
( )
T
4
T
1
1
between G
≈
.
370mV
R
2
IA
OUT
.
G
OUT
1
OUT
= 2...11:
by the following relation:
OUT
.
OUT
of the output stage. The offset of
1
has to be directly connected to
and increases the performance
IA
= 5mA. The gain G
1
= 10 for pre–amplifiing the
(V
BE
–Drift: –2mV/°C typ.)
AM417
OUT
April 99
is ad-
4/6
1