EVAL-ADE7880EBZ View Datasheet(PDF) - Analog Devices
Part Name
Description
MFG CO.
'EVAL-ADE7880EBZ' PDF : 107 Pages View PDF
ADE7880
POWER-UP PROCEDURE
3.3V – 10%
2.0V ± 10%
Data Sheet
ADE7880
PSM0 READY
0V
MICROPROCESSOR
SETS PM1 PIN TO 0;
APPLY VDD TO CHIP
~26ms
~40ms
POR TIMER
TURNED ON
ADE7880
FULLY
POWERED UP
Figure 35. Power-Up Procedure
MICROPROCESSOR
MAKES THE
RSTDONE CHOICE BETWEEN
INTERRUPT I2C AND SPI
TRIGGERED
The ADE7880 contains an on-chip power supply monitor that
supervises the power supply (VDD). At power-up, the device is
inactive until VDD reaches 2.0 V ± 10%. When VDD crosses
this threshold, the power supply monitor keeps the device in the
inactive state for an additional 26 ms to allow VDD to rise to
3.3 V − 10%, the minimum recommended supply voltage.
The PM0 and PM1 pins have internal pull-up resistors, but it is
necessary to set the PM1 pin to Logic 0, either through a micro-
controller or by grounding the PM1 pin externally, before powering
up the chip. The PM0 pin can remain open as it is held high, due
to the internal pull-up resistor. This ensures that the ADE7880
always powers up in PSM0 (normal) mode. The time from the chip
being powered up completely to all functionality being enabled
is about 40 ms (see Figure 35). It is necessary to ensure that the
RESET pin is held high during the entire power-up procedure.
If PSM0 mode is the only desired power mode, the PM1 pin can
be tied to ground externally. When the ADE7880 enters PSM0
mode, the I2C port is the active serial port. To use the SPI port,
toggle the SS/HSA pin three times from high to low.
To lock I2C as the active serial port, set Bit 1 (I2C_LOCK) of the
CONFIG2 register to 1. From this moment, the device ignores
spurious toggling of the SS/HSA pin, and a switch to the SPI
port is no longer possible.
Immediately after entering PSM0 mode, all registers in the
ADE7880 are set to their default values, including the
CONFIG2 and LPOILVL registers.
The ADE7880 signals the end of the transition period by pulling
the IRQ1 interrupt pin low and setting Bit 15 (RSTDONE) in
the STATUS1 register to 1. This bit is cleared to 0 during the
transition period and is set to 1 when the transition ends.
Writing the STATUS1 register with the RSTDONE bit set to 1
clears the status bit and returns the IRQ1 pin high. Because
RSTDONE is an unmaskable interrupt, Bit 15 (RSTDONE) in
the STATUS1 register must be cancelled for the IRQ1 pin to
return high. Wait until the IRQ1 pin goes low before accessing
the STATUS1 register to test the state of the RSTDONE bit. At
this point, as a good programming practice, cancel all other
status flags in the STATUS1 and STATUS0 registers by writing
the corresponding bits with 1.
Initially, the DSP is in idle mode and, therefore, does not execute
any instructions. This is the moment to initialize all registers in
the ADE7880. See the Digital Signal Processor section for the
proper procedure to initialize all registers and start the metering.
If the supply voltage, VDD, falls lower than 2.0 V ± 10%, the
ADE7880 enters an inactive state, which means that no
measurements or computations are executed.
If SPI is the active serial port, any write to the CONFIG2 register
locks the port, and a switch to the I2C port is no longer possible.
To use the I2C port, the ADE7880 must be powered down or the
device must be reset by setting the RESET pin low. After the serial
port is locked, the serial port selection is maintained when the
device changes from one PSMx power mode to another.
If the RESET pin is held low while the IC powers up or if the
power-up sequence timing cannot be maintained as per
Figure 35, perform the following sequence of write operations
prior to starting the DSP (setting the RUN register to 0x01), to
ensure that the modulators are reset properly.
1. 8-bit write: 0xAD is written at Address 0xE7FE.
2. 8-bit write: 0x14 is written at Address 0xE7E2.
3. Wait 200 μs.
4. 8-bit write: 0xAD is written at Address 0xE7FE.
5. 8-bit write: 0x04 is written at Address 0xE7E2.
Rev. C | Page 24 of 107
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