MAXQ3180-RAN+ datasheet(7/48 Pages) MAXIM

7 / 48 page

Low-Power, Multifunction, Polyphase AFE

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Detailed Description

Operating Modes

The MAXQ3180 has four basic modes of operation,

each of which is described in the following sections.

The Initialization Mode is the default mode upon power-

up or following reset; entry to and exit from the other

operating modes is only performed as a result of com-

mands sent by the master.

Initialization Mode

This is the default operating mode for the MAXQ3180

following reset, power-up, or a switch into or out of Low-

Power Measurement Mode (LPMM). In this mode, no

power measurements are taken because the

MAXQ3180 has not yet been configured. When entering

this mode, the MAXQ3180 sets the status flag NOINIT to

1 and drives the IRQ pin low to indicate to the master

that initialization is required. The master is responsible

for performing the following series of operations:

• Interrogating the MAXQ3180 to determine that the

NOINIT bit has been set.

• Loading all RAM configuration registers with appro-

priate values.

• Clearing the NOINIT bit to zero.

Once the NOINIT bit has been cleared to zero, the

MAXQ3180 exits Initialization Mode and enters Run

Mode (or LPMM mode if LOWPM = 1). It is the master’s

responsibility to ensure that all configuration registers

have been set to their correct values before clearing

the NOINIT bit.

Run Mode

This mode is the normal operating mode for the

MAXQ3180. In this mode, the MAXQ3180 continuously

executes the following operations:

• Scans analog front-end channels and collects raw

voltage and current samples.

• Processes voltage and current samples through DSP

filters as enabled and configured.

• Calculates power, energy, and other required quanti-

ties and stores these values in RAM registers.

• Responds to register write and read commands from

the master.

• Outputs power pulses on CFP and CFQ as configured.

• Drives IRQ when an interrupt condition has been

detected and the interrupt is not masked.

Low-Power Measurement Mode (LPMM)

This mode allows the MAXQ3180 to perform all normal

electric-metering functions while operating at a

reduced clock rate to conserve power. In this mode,

the MAXQ3180 switches its system clock from the high-

frequency external crystal (or external clock source) to

its internal RC oscillator. The actual system clock fre-

quency used is the RC oscillator output frequency

divided by 8, which results in a system clock frequency

of approximately 1MHz.

Entry to LPMM Mode only occurs at the request of the

master. The master must set the LOWPM bit (STATUS.2)

to 1 to place the MAXQ3180 into LPMM mode. Setting

this bit automatically sets the NOINIT bit and returns

the device to Initialization Mode. This is done because

changing the clock frequency invalidates a number of

configuration registers, which need to be reinitialized

with new, updated values before metering-measure-

ment operations can continue. Note that it is also possi-

ble to set LOWPM = 1 (and load configuration registers

appropriately) immediately following reset, which caus-

es the MAXQ3180 to transition directly from Initialization

Mode to LPMM Mode once NOINIT has been cleared

by the master.

The master can also instruct the MAXQ3180 to exit

LPMM Mode by clearing the LOWPM bit. This causes

NOINIT to be set as with LPMM entry, and the master

must reset the appropriate configuration registers and

clear NOINIT to allow measurement to continue.

Stop Mode

This mode places the MAXQ3180 into a power-saving

state where it consumes the least possible amount of

current. In Stop Mode, all functions are suspended,

including the ADC and power and voltage measurement

and processing. The MAXQ3180 does not respond to

any commands from the master in this operating state.

Entry into Stop Mode only occurs at the request of the

master. To place the MAXQ3180 into Stop Mode, the

master must set the STOPM bit (STATUS.1) to 1. Once

this bit has been written, the MAXQ3180 enters Stop

Mode immediately following the end of the register

write command (after the transmission of the final ACK

byte by the MAXQ3180).

There are three possible ways to bring the MAXQ3180

back out of Stop Mode.

• Power Cycle. The MAXQ3180 automatically exits

Stop Mode if a power-on reset occurs. Following exit

from Stop Mode, all registers are cleared back to

their default states, and the MAXQ3180 transitions to

Initialization Mode.

• External Reset. The MAXQ3180 exits Stop Mode if

an external reset is triggered by driving RESET low.

Once the RESET pin is released and allowed to

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