MCP3909_12 Datasheet, PDF (16/44 Pages) Microchip Technology – Energy Metering IC with SPI Interface and Active Power Pulse Output

MCP3909
3.3 Analog V_DD (AV_DD)
AV_DD is the power supply pin for the analog circuitry
within the MCP3909.
This pin requires appropriate bypass capacitors and
should be maintained to 5V ±10% for specified
operation. Refer to Section 6.0 “Applications
Information”.
3.4 Current Channel (CH0-, CH0+)
CH0- and CH0+ are the fully differential analog voltage
input channels for the current measurement, containing
a PGA for small-signal input, such as shunt current
sensing. The linear and specified region of this channel
is dependant on the PGA gain. This corresponds to a
maximum differential voltage of ±470 mV/G and maxi-
mum absolute voltage, with respect to A_GND, of ±1V.
Up to ±6V can be applied to these pins without the risk
of permanent damage.
Refer to Section 1.0 “Electrical Characteristics”.
3.5 Voltage Channel (CH1-,CH1+)
CH1- and CH1+ are the fully differential analog voltage
input channels for the voltage measurement. The linear
and specified region of these channels have a maxi-
mum differential voltage of ±660 mV and a maximum
absolute voltage of ±1V, with respect to A_GND. Up to
±6V can be applied to these pins without the risk of per-
manent damage.
Refer to Section 1.0 “Electrical Characteristics”.
3.6 Master Clear (MCLR)
MCLR controls the reset for both delta-sigma ADCs, all
digital registers, the SINC filters for each channel and
all accumulators post multiplier. The MCLR pin is also
used to change pin functionality and enter the serial
interface mode. A logic ‘0’ resets all registers and holds
both ADCs in a Reset condition. The charge stored in
both ADCs is flushed and their output is maintained to
0x0000h. The only block consuming power on the
digital power supply during Reset is the oscillator
circuit.
3.7 Reference (REFIN/OUT)
REFIN/OUT is the output for the internal 2.4V refer-
ence. This reference has a typical temperature coeffi-
cient of 15 ppm/°C and a tolerance of ±2%. In addition,
an external reference can also be used by applying
voltage to this pin within the specified range. This pin
requires appropriate bypass capacitors to A_GND, even
when using the internal reference only.
Refer to Section 6.0 “Applications Information”.
3.8 Analog Ground (A_GND)
A_GND is the ground connection to internal analog cir-
cuitry (ADCs, PGA, band gap reference, POR). To
ensure accuracy and noise cancellation, this pin must
be connected to the same ground as D_GND, preferably
with a star connection. If an analog ground plane is
available, it is recommended that this device be tied to
this plane of the PCB. This plane should also reference
all other analog circuitry in the system.
3.9 Serial Clock Input or F2 Frequency
Control Pin
This dual function pin can act as either the serial clock
input for SPI communication or the F2 selection for the
high-frequency output and low-frequency output pin
ranges, changing the value of the constants F_C and
H_FC used in the device transfer function. F_C and H_FC
are the frequency constants that define the period of
the output pulses for the device.
3.10 Serial Data Input or F1 Frequency
Control Pin
This dual function pin can act as either the serial data
input for SPI communication or the F1 selection for the
high-frequency output and low-frequency output pin
ranges, changing the value of the constants F_C and
H_FC used in the device transfer function. F_C and H_FC
are the frequency constants that define the period of
the output pulses for the device.
3.11 Chip Select (CS) or F0 Frequency
Control Pin
This dual function pin can act as either the chip select
for SPI communication or the F0 selection for the high-
frequency output and low-frequency output pin ranges
by changing the value of the constants F_C and H_FC
used in the device transfer function. F_C and H_FC are
the frequency constants that define the period of the
output pulses for the device.
3.12 Gain Control Logic Pins (G1, G0)
G1 and G0 select the PGA gain (G) on Channel 0 from
four different values: 1, 2, 8 and 16.
DS22025C-page 16
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