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ADE7978/ADE7933/ADE7932/ADE7923

Data Sheet

Rev. D | Page 84 of 125

POWER-UP PROCEDURE

The ADE7978/ADE7933/ADE7932/ADE7923 chipset contains

on-chip power supply monitors that supervise the power supply

(VDD). The ADE7933/ADE7932 and ADE7923 have a monitor

with a threshold at 2.0 V ± 10% and a timeout timer of 23 ms.

The ADE7978 has a monitor with a threshold between 2.5 V

and 2.6 V and a time-out timer of 32 ms. Because the ADE7933/

ADE7932 and ADE7923 are fully managed by the ADE7978,

the power supply monitor of the ADE7978 determines the

power-up of the chipset.

The ADE7978 is in an inactive state until VDD reaches the thresh-

old of 2.5 V to 2.6 V. The ADE7933/ADE7932 and ADE7923 are

also in an inactive state. Before the chipset is powered up, ensure

that the power supply for the ADE7978 ensures a transition from

around 2.5 V or 2.6 V to 3.3 V − 10% in less than 32 ms. Figure 107

shows the power-up procedure, which follows these steps:

1. When VDD crosses the 2.5 V to 2.6 V threshold, the

ADE7978 power supply monitor keeps the chip in the

inactive state for an additional 32 ms, allowing VDD to reach

3.3 V − 10%, the minimum recommended supply voltage.

2. The ADE7978 starts to function and generates a 4.096 MHz

clock signal for the ADE7933/ADE7932 and ADE7923 at the

CLKOUT pin.

3. The ADE7933/ADE7932 and ADE7923 devices begin to

function.

4. After 20 µs, the ADE7978 resets the ADE7933/ADE7932

and ADE7923 devices by setting the RESET_EN pin low.

The ADE7978 toggles the following pins eight times from

high to low at a 4.096 MHz frequency (CLKIN/4): VT_A,

VT_B, VT_C, and VT_N.

5. The ADE7933/ADE7932 and ADE7923 devices begin to

function at default conditions.

6. When the ADE7978, the ADE7933/ADE7932 and

ADE7923 devices become fully functional, the IRQ1

interrupt pin is set low, and Bit 15 (RSTDONE) in the

STATUS1 register (Address 0xE503) is set to 1. This bit is

cleared to 0 during power-up and is set to 1 when the

power-up is completed.

7. After a power-up of the ADE7978, the I2C serial port is active.

For information about changing the serial port to SPI and

about locking in the selected serial port (I2C or SPI), see the

Serial Interface Selection section. Immediately after power-

up, the ADE7978 resets all registers to their default values.

After a successful power-up of the chipset, follow the instructions

in the Initializing the Chipset section.

If the supply voltage, VDD, falls below 2 V ± 10%, the ADE7978

and the ADE7933/ADE7932 and ADE7923 devices enter an

inactive state, which means that no measurements or

computations are executed.

INITIALIZING THE CHIPSET

After the ADE7978/ADE7933/ADE7932/ADE7923 are powered

up, initialize the chipset as follows.

1. Monitor the IRQ1 pin until it goes low, indicating that the

RSTDONE interrupt is triggered.

2. When the ADE7978 starts functioning after power-up, the

I2C port is the active serial port. If SPI communication is

to be used, toggle the SS/HSA pin three times from high to

low to select the SPI interface. For more information about

changing the communication port to SPI, see the Serial

Interface Selection section.

3. Read the STATUS1 register (Address 0xE503) to verify that

Bit 15 (RSTDONE) is set to 1, and then write a 1 to the bit

to clear it. The IRQ1 pin returns high. Because RSTDONE

is an unmaskable interrupt, Bit 15 (RSTDONE) must be

reset to 0 for the IRQ1 pin to return high.

It is recommended that all other flags in the STATUS1 and

STATUS0 registers also be reset by writing a 1 to all bits in

the registers.

20µs

ADE7978,

ADE7933/ADE7932

AND ADE7923

POWERED UP.

3.3V – 10%

2.5V TO 2.6V

ADE7978 STARTS

FUNCTIONING. ADE7978

CLOCKS ADE7933/ADE7932

AND ADE7923.

32ms

ADE7978 POR

TIMER TURNED ON.

RSTDONE

INTERRUPT

TRIGGERED.

ADE7978,

ADE7933/ADE7932

AND ADE7923 READY.

50ms

MICROPROCESSOR

MAKES THE CHOICE

BETWEEN I2C AND SPI.

ADE7978 RESETS ADE7933/ADE7932 AND ADE7923.

ADE7933/ADE7932 AND ADE7923 START FUNCTIONING.

Figure 107. Power-Up Procedure

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