SM6661A Datasheet, PDF (7/14 Pages) Nippon Precision Circuits Inc – Post-amplifier for Gyroscope

SM6661A
FUNCTIONAL DESCRIPTION
Sensor Signal Input and Output
The signal output of gyroscope IC is connected to VSIG_IN1 pin. The first stage amplifier of SM6661A is dif-
ferential input, so that VREF_IN1 pin is input zero-rate voltage of gyroscope IC.
(Normally, the reference voltage output pin of gyroscope IC should be connected to VREF_IN1 pin.)
The amplified signal is output from VSIG_OUT1 pin. Note that the output signal is reverse phase of input sig-
nal from VSIG_IN1 pin. The zero-rate voltage of output signal is V_CC/2V. The description of VSIG_IN2,
VREF_IN2 and VSIG_OUT2 pins are the same as above VSIG_IN1, VREF_IN1 and VSIG_OUT1 pins.
VCC/2 Pin
The VCC/2 pin is a reference voltage pin. Smoothing capacitors should be connected between VCC/2 pin and
GND. The recommended values of smoothing capacitors are parallel-connected 10µF electrolytic capacitor
and 0.1µF ceramic capacitor.
Output Gain and Frequency Characteristics Setting
The output gain and frequency characteristics of SM6661A are adjustable with connecting external resistors
and capacitors as shown below.
C2
C1 R1
HPF1
HPF2
R2
GAIN1
GAIN2
VSIG_OUT1
VSIG_OUT2
−
AMP
30dB
+
−
AMP
0 to 20dB
+
Output gain setting
The output gain of SM6661A is adjustable by changing the value of external resistors R₁ and R₂. The
SM6661A has a built-in 30dB amplifier, so that the output gain “Gain2” is determined by the formula below;
Gain2 = 20 × log ( ^R2 ) + 30 [dB]
R₁
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