MCP6G04 Microchip Technology, MCP6G04 Datasheet - Page 23

• Manufacturer Part Number: MCP6G04
• Description: 110 Selectable Gain Amplifier
• Manufacturer: Microchip Technology

4.7
An unused amplifier in a quad package (MCP6G04)
should be configured as shown in
circuit prevents the output from toggling and causing
crosstalk. Because the V
circuit, the GSEL voltage is automatically set at V
and the gain is 1 V/V. The output pin provides a
buffered V
current draw of the unused amplifier.
FIGURE 4-8:
4.8
4.8.1
The circuit in
pin to drive the Gain Select input (GSEL). Setting the
GPIO pin to logic low, high-Z or logic high gives a GSEL
voltage of 0V, V
50).
FIGURE 4-9:
The microcontroller’s GPIO pin cannot produce a
leakage current of more than ±1 µA for this circuit to
function properly. In noisy environments, a capacitor
may need to be added to the GPIO pin.
© 2006 Microchip Technology Inc.
MCU
V
DD
GPIO
Unused Amplifiers
Typical Applications
Pin
¼ MCP6G04
DD
DRIVING THE GAIN SELECT PIN
WITH A MICROCONTROLLER GPIO
PIN
GSEL
/2 voltage and minimizes the supply
Figure 4-9
DD
V
V
IN
IN
/2 or V
MCP6G0X
GSEL
Unused Amplifiers.
Driving the GSEL Pin.
V
DD
uses a microcontroller GPIO
DD
IN
, respectively (G = 10, 1 or
pin looks like an open
MCP6G0X
V
DD
Figure
V
OUT
4-8. This
V
OUT
DD
/2,
4.8.2
The circuit in
microcontroller (100 kHz clock rate) to drive the Gain
Select input (GSEL). Setting the PWM duty cycle to
0%, 50% or 100% gives a GSEL voltage of 0V, V
or V
FIGURE 4-10:
The PWM clock rate needs to be fast so it is easily
filtered and does not interfere with the desired signal,
and it needs to be slow enough for good accuracy and
low crosstalk. This filter reduces the ripple at the GSEL
pin to about 7 mV
time is about 200 µs; the filter limits how quickly the
gain can be changed. Scale the resistors and/or
capacitors for other clock rates, or for different ripple.
4.8.3
Figure 4-11
I
the gain on the SGA. Just as a hand-held multimeter
uses different measurement ranges to obtain the best
results, this circuit makes it easy to set a high gain for
small signals and a low gain for large signals. As a
result, the required dynamic range at the SGA’s output
is less than at its input (by up to 34 dB).
FIGURE 4-11:
Current Measurement Circuit.
X
. The circuit’s performance benefits from changing
PIC MCU
DD
V
Output
, respectively (G = 10, 1 or 50).
DD
PWM
I
X
DRIVING THE GAIN SELECT PIN
WITH A PWM SIGNAL
GAIN RANGING
shows a circuit that measures the current
Figure 4-10
MCP6G01/2/3/4
V
10 kΩ
IN
P-P
R
S
at V
GSEL
Driving the GSEL Pin.
Wide Dynamic Range
MCP6G0X
uses a PWM output on a PIC
DD
4.7 nF
10 kΩ
= 5.0V. The 10% settling
MCP6G0X
V
DD
DS22004A-page 23
4.7 nF
V
OUT
V
OUT
DD
/2