MCP3551-ESLASHMS datasheet(19/36 Pages) MICROCHIP

19 / 36 page

DS21950E-page 19

MCP3550/1/3

Once a power-up event has occurred, the device must

require additional time before a conversion can take

place. During this time, all internal analog circuitry must

settle before the first conversion can occur. An internal

timer counts 32 internal clock periods before the

internal oscillator can provide clock to the conversion

process. This allows all internal analog circuitry to

settle to their proper operating point. This timing is

typically less than 300 µs, which is negligible compared

to one conversion time (e.g. 72.7 ms for the

MCP3551). Figure 4-6 illustrates the conditions for a

power-up and power-down event under typical start-up

conditions.

FIGURE 4-6:

Power-On Reset Operation.

4.7

Shutdown Mode

When not internally converting, the two modes of

operation for the MCP3550/1/3 devices are the

Shutdown and Sleep modes. During Shutdown mode,

all internal analog circuitry, including the POR, is turned

off and the device consumes less than 1 µA. When

exiting Shutdown mode, the device must require

additional time before a conversion can take place.

During this time, all internal analog circuitry must settle

before the first conversion can occur. An internal timer

counts 32 internal clock periods before the internal

oscillator can provide clock to the conversion process.

This allows all internal analog circuitry to settle to their

proper operating point. This timing is typically less than

300 µs, which is negligible compared to one conversion

time (72.7 ms for MCP3551).

4.8

Sleep Mode

During Sleep mode, the device is not converting and is

awaiting data retrieval; the internal analog circuitry is

still running and the device typically consumes 10 µA.

In order to restart a conversion while in Sleep mode,

toggling CS to a logic-high (placing the part in Shut-

down mode) and then back to a logic-low will restart the

conversion. Sleep can only be entered in Single

Conversion mode. Once a conversion is complete in

Single Conversion mode, the device automatically

enters Sleep mode.

VDD

2.2V

2.0V

Reset

Normal

Operation

Reset

Start-up

Time

300 µs

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