AM417 datasheet(4/6 Pages) AME

4 / 6 page

RATIOMETRIC VOLTAGE TRANSMITTER

AM417

analog microelectronics

April 99

4/6

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:

VCC

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 col-

lector stage T1 which is able to push a maximum current of IOUT = 5mA. The gain GOUT is ad-

justable by the external resistors R3 and R4 between GOUT = 2...11:

OUT =

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

()

OUT

VCC

max

=−15

1 .

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:

()

OUT

TRESH

max =

−

≈

370mV

If no current limitation is required, the Emitter of the transistor T1 has to be directly connected to

VCC (R2 = 0

Ω). 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).

AM417 Datasheet(PDF) 4 Page - Analog Microelectronics

AM417 Datasheet(HTML) 4 Page - Analog Microelectronics

Html Pages

1 2 3 4 5 6

Datasheet Download

Link URL