MCP3564-ESLASHST datasheet(46/108 Pages) MICROCHIP

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MCP3561/2/4

DS20006181C-page 46

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5.9

Low-Power Shutdown Modes

The device incorporates two low-power modes that can

be activated in order to limit power consumption of the

device when ADC is not used. These two modes are

called Partial Shutdown and Full Shutdown modes.

5.9.1

FULL SHUTDOWN MODE

The Full Shutdown mode can be enabled by two

means:

• Writing CONFIG0 to ‘0x00’

• Sending a Fast Command Full Shutdown (Fast

Command code: ‘1101’)

Full Shutdown mode is the lowest power mode of the

device. None of the circuits consuming static power are

active in this mode.

As stated in Section 5.7 “Power-on Reset”, the

AVDD/DVDD POR monitoring circuits are not active

while in Full Shutdown mode. For this reason, the Full

Shutdown mode is not recommended for applications

where an AVDD/DVDD power-down (whether expected

or unexpected) voltage level of 100 mV (approx.) or

less cannot be ensured before reapplying power.

The part can still be accessed through the SPI interface

during this mode and will accept incoming SPI

commands. The ADCDATA register is not cleared

during Full Shutdown mode and still holds previous

conversion results. The other Configuration register

settings are not modified or reset due to entering in Full

Shutdown mode.

When the ADC_MODE[1:0] bits are temporarily set

internally to ‘00’ during SCAN mode, in between scan

cycles, the part does not go into Full Shutdown mode,

even if all the other bits in the CONFIG0 register are set

to ‘0’.

The Full Shutdown mode stops all internal timers and

resets them. Sending a Fast CMD to change the

operating mode exits the Full Shutdown mode.

The user should place all digital inputs to a static value

(logic low or high) in order to optimize power

consumption during Full Shutdown mode. The current

consumption specifications during Full Shutdown

mode are intended without any digital pin toggling

during the measurement. In this case, only leakage

current is consumed throughout the device and this

current varies exponentially with respect to absolute

temperature.

5.9.2

PARTIAL SHUTDOWN MODE

Partial Shutdown mode is achieved when CONFIG0 is

set to ‘xx000000’, where ‘xx’ is not equal to ‘00’.

(CONFIG0 = 0x00 puts the device in Full Shutdown

mode). In this mode, most of the internal circuits are

shut down, with the exception of the POR monitoring

and internal biasing circuits. During the Partial

Shutdown mode, the power supply is continuously

monitored, whereas in Full Shutdown mode, the POR

monitoring circuits are powered down. The power

consumption is also much higher in Partial Shutdown

mode due to different biases and the POR monitoring

circuits being active. Partial Shutdown mode allows the

device to be restarted and put back in Conversion

mode faster than Full Shutdown mode. Table 5-10

describes the differences between Partial and Full

Shutdown modes. If the current consumption of Partial

Shutdown mode is acceptable for the application, it is

recommended that it is used as an alternative to Full

Shutdown mode, where the POR monitoring circuits

are shut down and no longer monitoring the AVDD and

DVDD power supplies.

TABLE 5-10:

LOW-POWER MODES(1)

Device

Low-Power Mode

CONFIG0[7:6] CLK_SEL[1:0] CS_SEL[1:0] ADC_MODE[1:0]

Description

Partial Shutdown

All peripherals, except the

POR monitoring circuits and

clock biasing circuits, are shut

down and consume no static

current.The SPI interface

remains active in this mode

and consumes no current

while the bus is Idle.

Full Shutdown

All analog and digital circuits

are shut down and consume

no static current. The SPI

interface remains active in this

mode and consumes no

current while the bus is Idle.

Note 1: x =Don’t Care

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