ADE7754AR Analog Devices Inc, ADE7754AR Datasheet - Page 28

• Manufacturer Part Number: ADE7754AR
• Description: IC ENERY METER 3PHASE 24-SOIC
• Manufacturer: Analog Devices Inc

Specifications of ADE7754AR

• Input Impedance: 370 KOhm
• Measurement Error: 0.1%
• Voltage - I/o High: 2.4V
• Voltage - I/o Low: 0.8V
• Current - Supply: 7mA
• Voltage - Supply: 4.75 V ~ 5.25 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 24-SOIC (0.300", 7.50mm Width)
• Meter Type: 3 Phase
• For Use With: EVAL-ADE7754EBZ - BOARD EVALAUTION FOR ADE7754
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Other names: AD71049AR; AD71049AR

ADE7754
SERIAL INTERFACE
ADE7754 has a built-in SPI interface. The serial interface of
the ADE7754 is made of four signals: SCLK, DIN, DOUT,
and CS. The serial clock for a data transfer is applied at the
SCLK logic input, which has a Schmidt-trigger input structure
that allows slow rising (and falling) clock edges to be used. All
data transfer operations are synchronized to the serial clock.
Data is shifted into the ADE7754 at the DIN logic input on the
falling edge of SCLK. Data is shifted out of the ADE7754 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 ADE7754 into 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
ADE7754 is the only device on the serial bus. However, with
CS tied low, all initiated data transfer operations must be fully
completed (i.e., the LSB of each register must be transferred
because there is no other way to bring the ADE7754 back into
communications mode without resetting the entire device,
i.e., setting the RESET pin logic low).
All the ADE7754 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
ADE7754 is placed into communications mode. In communica-
tions mode, the ADE7754 expects the first communication to
be a write to the internal communications register. The data
written to the communications register contains the address and
specifies the next data transfer to be a read or a write command.
Therefore all data transfer operations with the ADE7754,
whether read or write types, must begin with a write to the
communications register.
The communications register is an 8-bit write-only register. The
MSB determines whether the next data transfer operation is a
read or a write. The six LSBs contain the address of the register
to be accessed. See the Communications Register section for a
more detailed description.
DOUT
DIN
Figure 41. Addressing ADE7754 Registers via the
Communications Register
COMMUNICATIONS REGISTER
REGISTER n-1
REGISTER 1
REGISTER 2
REGISTER 3
REGISTER n
OUT
OUT
OUT
OUT
OUT
IN
IN
IN
IN
IN
–28–
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 ADE7754 once again enters com-
munications mode (i.e., the next instruction followed must be a
write to the communications register).
DOUT
SCLK
A data transfer is completed when the LSB of the ADE7754
register being addressed (for a write or a read) is transferred to
or from the ADE7754.
Serial Write Operation
The serial write sequence requires the following steps. With the
ADE7754 in communications mode and the CS input logic low,
a write to the communications register takes place. The MSB of
this byte transfer must be set to 1, indicating that the next data
transfer operation is a write to the register. The six LSBs of this
byte contain the address of the register to be written to. The
ADE7754 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.
As explained previously, the data write is initiated by a write to
the communications register, followed by the data. During a data
write operation to the ADE7754, data is transferred to all on-chip
registers one byte at a time. After a byte is transferred into the
serial port, there is a finite amount of time before the content of
the serial port buffer is transferred to one of the ADE7754 on-chip
registers. Although another byte transfer to the serial port can
start while the previous byte is being transferred to the destina-
tion register, this second byte transfer should not finish until at
least 1 µs after the end of the previous byte transfer. This func-
tionality is expressed in the timing specification t
If a write operation is aborted during a byte transfer (CS brought
high), then that byte will not be written to the destination register.
Destination registers may be up to 3 bytes wide. See the Register
Descriptions section. Therefore, the first byte shifted into the
serial port at DIN is transferred to the MSB (most significant
byte) of the destination register. If the destination register is 12 bits
wide, for example, a 2-byte data transfer must take place. The
data is always assumed to be right justified; therefore, in this
case, the four MSBs of the first byte would be ignored and the four
LSBs of the first byte written to the ADE7754 would be the four
MSBs of the 12-bit word. Figure 45 illustrates this example.
SCLK
DIN
DIN
CS
CS
COMMUNICATIONS REGISTER WRITE
COMMUNICATIONS REGISTER WRITE
Figure 42. Reading Data from the ADE7754 via the
Serial Interface
Figure 43. Writing Data to the ADE7754 via the
Serial Interface
1 0
0 0
ADDRESS
ADDRESS
MULTIBYTE READ DATA
MULTIBYTE WRITE DATA
6
. See Figure 44.
REV. 0