MXT1664T3-C2TESSQTP datasheet(26/98 Pages) MICROCHIP

26 / 98 page

MXT1664T3 2.0

DS40002054A-page 26

 2018 Microchip Technology Inc.

5.0

POWER-UP / RESET REQUIREMENTS

5.1

Power-on Reset

There is an internal Power-on Reset (POR) in the device.

If an external reset is to be used the device must be held in RESET (active low) while the digital (Vdd), analog (AVdd)

and digital I/O (VddIO) power supplies are powering up. The supplies must have reached their nominal values before

the RESET signal is deasserted (that is, goes high). This is shown in Figure 5-1. See Section 14.2 “Recommended

Operating Conditions” for nominal values for the power supplies to the device.

FIGURE 5-1:

POWER SEQUENCING ON THE MXT1664T3

When using a boosted external XVdd power supply, Vdd must be applied to the device before the external XVdd supply

to ensure that the different power domains in the device are initialized correctly. Typically this can be done by connecting

the enable pin of the Switched-Mode Power Supply (SMPS) supplying XVdd to a 10 k

 pull-up resistor connected to

the Vdd, but the XVdd can be controlled separately by the host, if required.

If XVdd is not boosted, XVdd can be connected directly to Vdd to supply 3.3 V, in which case the two supplies can be

brought up together.

It is recommended that customer designs include the capability for the host to control all the maXTouch power supplies

and pull the RESET line low.

After power-up, the device typically takes 79 ms before it is ready to start communications.

If the RESET line is released before the AVdd or external XVDD supply has reached its nominal voltage (see Figure 5-2

on page 27), then some additional operations need to be carried out by the host. There are two options open to the host

controller:

• Start the part in deep sleep mode and then send the command sequence to set the cycle time to wake the part

and allow it to run normally. Note that in this case a calibration command is also needed.

• Send a RESET command.

CAUTION!

XVdd must not be grounded when Vdd is active as damage to the device may result.

> 0 ns

≥ 0 ns

Note:

When using external

at power-up, VddIO must not be enabled after Vdd.

RESET

(VddIO)

Vdd

AVdd

> 90 ns

VddIO

2) If Xvdd is powered from an external supply (not connected to Vdd),

should

XVdd

must obey the

ication.

e powered up after Vdd and

rate-of-rise specif

If XVdd is

(3.3V),

connected directly to Vdd

the two supplies can be brought up together.

Xvdd

(External)

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