MCP3465R datasheet(51/110 Pages) MICROCHIP

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DS20006414C-page 51

MCP3465R

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 send-

ing 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 com-

mands. 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 Par-

tial Shutdown mode, the power supply is continuously

monitored, whereas in Full Shutdown mode, the POR

monitoring circuits are powered down. The power con-

sumption 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 mon-

itoring circuits are shut down and no longer monitoring

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 bias-

ing 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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