EVAL-ADE7759E AD [Analog Devices], EVAL-ADE7759E Datasheet - Page 26

• Manufacturer Part Number: EVAL-ADE7759E
• Description: Active Energy Metering IC with di/dt Sensor Interface
• Manufacturer: AD [Analog Devices]

ADE7759
Table III. Frequency Dependencies of the ADE7759 Parameters
Parameter
Nyquist frequency for CH 1 and 2 ADCs CLKIN/8
PHCAL resolution (seconds per LSB)
Active Energy register update rate (Hz)
Waveform sampling rate (Number of
samples per second)
WAVSEL 1, 0 = 0 0
Maximum ZXTOUT period
SUSPENDING THE ADE7759 FUNCTIONALITY
The analog and the digital circuit can be suspended separately.
The analog portion of the ADE7759 can be suspended by setting
the ASUSPEND bit (Bit 4) of the mode register to logic high—
see Mode Register. In suspend mode, all waveform samples from
the ADCs will be set to zeros. The digital circuitry can be halted
by stopping the CLKIN input and maintaining a logic high or
low on CLKIN pin. The ADE7759 can be reactivated by restoring
the CLKIN input and setting the ASUSPEND bit to logic low.
APPLICATION INFORMATION
Application note AN-564 contains detailed information on how to
design a ANSI Class 100 Watt-Hour meter based on the ADE7756,
a pin-to-pin compatible product with the ADE7759. Application
Note AN-578 describes an algorithm on how to calculate the voltage
and current rms values using an external MCU. It is available from
the ADE7756 product homepage under the Application Note link
on the energy metering homepage, www.analog.com/energymeter.
SERIAL INTERFACE
All ADE7759 functionality is accessible via several on-chip
registers—see Figure 41. The contents of these registers can be
updated or read using the on-chip serial interface. After power-on
or toggling the RESET pin low or a falling edge on CS, the
ADE7759 is placed in communications mode. In communications
mode the ADE7759 expects a write to its Communications register.
The data written to the Communications register determines
whether the next data transfer operation will be a read or a write
and also which register is accessed. Therefore, all data transfer
operations with the ADE7759, whether a read or a write, must
begin with a write to the Communications register.
DOUT
DIN
0 1
1 0
1 1
REGISTER #1
REGISTER #2
REGISTER #3
REGISTER #n –1
REGISTER #n
COMMUNICATIONS
REGISTER
OUT
OUT
OUT
OUT
OUT
IN
IN
IN
IN
IN
CLKIN Dependency
4/CLKIN
CLKIN/4
CLKIN/128
CLKIN/256
CLKIN/512
CLKIN/1024
524,288/CLKIN
REGISTER
ADDRESS
DECODE
The Communications register is an 8-bit wide register. The MSB
determines whether the next data transfer operation is a read or
a write. The five LSBs contain the address of the register to be
accessed. See Communications Register section for a more
detailed description. Figure 42 and Figure 43 show the data
transfer sequences for a read and write operation, respectively.
On completion of a data transfer (read or write) the ADE7759
once again enters communications mode.
A data transfer is complete when the LSB of the ADE7759
register being addressed (for a write or a read) is transferred to
or from the ADE7759.
The Serial Interface of the ADE7759 is made up of four signals:
SCLK, DIN, DOUT and CS. The serial clock for a data transfer is
applied at the SCLK logic input. This logic input has a Schmitt-
trigger input structure, which allows slow rising (and falling)
clock edges to be used. All data transfer operations are synchro-
nized to the serial clock. Data is shifted into the ADE7759 at the
DIN logic input on the falling edge of SCLK. Data is shifted out
of the ADE7759 at the DOUT logic output on a rising edge of
SCLK. The CS logic input is the chip select input. This input is
used when multiple devices share the serial bus. A falling edge on
CS also resets the serial interface and places the ADE7759 in
communications mode. The CS input should be driven low for
the entire data transfer operation. Bringing CS high during a data
transfer operation will abort the transfer and place the serial bus
in a high impedance state. The CS logic input may be tied low if
the ADE7759 is the only device on the serial bus. However with CS
tied low, all initiated data transfer operations must be fully com-
pleted, i.e., the LSB of each register must be transferred as there is
no other way of bringing the ADE7759 back into communications
mode without resetting the entire device, i.e., using RESET.
Serial Write Operation
The serial write sequence takes place as follows. With the ADE7759
in communications mode (i.e., the CS input logic low), a write to
the Communications register first takes place. The MSB of this
byte transfer is a 1, indicating that the data transfer operation is
a write. The LSBs of this byte contain the address of the register
to be written to. The ADE7759 starts shifting in the register data
on the next falling edge of SCLK. All remaining bits of register
data are shifted in on the falling edge of subsequent SCLK
pulses—see Figure 44.
DOUT
SCLK
SCLK
DIN
DIN
CS
CS
COMMUNICATIONS REGISTER WRITE
COMMUNICATIONS REGISTER WRITE
1
0
0
0
0
0
ADDRESS
ADDRESS
MULTIBYTE READ DATA
MULTIBYTE WRITE DATA