MCP3565R datasheet(51/108 Pages) MICROCHIP

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DS20006401C-page 51

MCP3565R

5.10 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.

5.10.1

FULL SHUTDOWN MODE

The Full Shutdown mode can only be enabled by

sending a Fast Command Full Shutdown (Fast

Command code: ‘1101’). Note that the execution of this

Fast command forces the CONFIG0 to be set to 0x00

(no active block is enabled).

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 5.8 “Power-on Reset”, the

AVDD/DVDD POR monitoring circuits are not active

while in Full Shutdown mode.

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 register settings are not modified or

reset due to entering Full Shutdown mode.

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 con-

sumption 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.

5.10.2

PARTIAL SHUTDOWN MODE

Partial Shutdown mode is achieved when CONFIG0 is

set to ‘0000000x’. 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 continu-

ously 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 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 5-11 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 monitor-

ing the AVDD and DVDD power supplies.

Note:

If the digital power supply resides for a long

time period below the POR threshold and

to a sufficiently low voltage (typically below

0.6V), some bits previously set to ‘1’ can

toggle to ‘0’ and not be set properly.

In order to ensure a safe operation after

the Full Shutdown mode, follow the

sequence of commands:

- Write LOCK register to 0xA5

- Write IRQ register to 0x07

- Send a Fast CMD Full Reset (‘1110’)

- Reconfigure the chip as desired

This sequence ensures a recovery with

the desired settings in any loss-of-power

scenario.

TABLE 5-11: LOW-POWER MODES(1)

Device

Low-Power Mode VREF_SEL

CONFIG0[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 = Do not care

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