21

NXP Semiconductors

CD1020

and reports the Wake event. In cases where CS_B is used to wake the device, the first MISO data message is not valid.

The LPM command contains setting of the polling timer, as shown in Table 23. The polling timer is used periodically to poll the inputs

to check for change of state. The low-power mode voltage threshold allows the user to determine the noise immunity versus lower current

levels that polling allows. Figure 13 shows the polling operation.

When an input is determined to meet the condition Open (when entering LPM), yet while Open (on polling event) the chip does not

continue the polling event for that input(s) to lower current in the chip (Figure 12 shows SG, SB is logically the same).

Figure 12. Low-power mode polling check

Figure 13. Low-power mode typical timing

La

tch

volt

ag

e

Compare voltage to initial

(Delta > 0.25 or > 4.0v)

LPM Voltage threshold

(~0.25v)

Polling timer

(64ms def)

Voltage on SG pin

End Polling (current off if

no change detected)

55µs

CS_B

Polling Time

Polling startup

Tactive time

Mode

Normal

LPM

Normal

Go To LPM

64ms (config)

78us

58us

20us

IC Current

330uA

20uA

Load

Current

X * 1mA SG

(2mA SB)

0uA