MXT1664T3-ABESSQTP datasheet(61/98 Pages) MICROCHIP

61 / 98 page

MXT1664T3 2.0

 2018 Microchip Technology Inc.

DS40002054A-page 61

11.4

Voltage Regulators

Each supply rail requires a Low Drop-Out (LDO) voltage regulator, although an LDO can be shared where supply rails

share the same voltage level.

Figure 11-1 shows an example circuit for an LDO.

FIGURE 11-1:

EXAMPLE LDO CIRCUIT

An LDO regulator should be chosen that provides adequate output capability, low noise, good load regulation and step

response. The voltage regulators listed in Table 11-1 have been tested and found to work well with maXTouch devices.

If it is desired to use an alternative LDO, however, certain performance criteria should be verified before using the

device. These are:

• Stable with high value multi-layer ceramic capacitors on the output

• Low output noise – ideally less than 100 µVRMS over the range 10 Hz to 1 MHz

• Good load transient response – this should be less than 35 mV peak when a load step change of 100 mA is

applied at the device output terminal

• No-load stable – Some LDOs become unstable if the output current falls below a certain minimum. If this is the

case, then this minimum must be lower than the minimum current consumed by the mXT1664T3 (for example, in

deep sleep).

TABLE 11-1:

SUITABLE LDO REGULATORS

Manufacturer

Device

Current Rating (mA)

Microchip Technology Inc.

MCP1824

300

Microchip Technology Inc.

MCP1824S

300

Microchip Technology Inc.

MAQ5300

300

Microchip Technology Inc.

MCP1725

500

Microchip Technology Inc.

MIC5323

300

Analog Devices

ADP122/ADP123

300

Diodes Inc.

AP2125

300

Diodes Inc.

AP7335

300

Linear Technology

LT1763CS8-3.3

500

NXP

LD6836

300

Texas Instruments

LP3981

300

Note

Some manufacturers claim that minimal or no capacitance is required for correct regulator operation. However, in all

cases, a minimum of a 1.0 µF ceramic, low ESR capacitor at the input and output of these devices should be used. The

manufacturer’s datasheets should always be referred to when selecting capacitors for these devices and the typical

recommended values, types and dielectrics adhered to.

A“soft-start” regulator with excellent noise and load step regulation will be needed to satisfy the XVdd supply

requirements. 1% resistors should be used to define the nominal output voltage. If 5% resistors are used, the nominal

XVdd voltage must be reduced accordingly to ensure that the recommended voltage range is adhered to.

SUPPLY FROM HOST

GND

VIN

SHDN

VOUT

SENSE/ADI

BYP

SUPPLY TO MAXTOUCH DEVICE

MXT1664T3-ABESSQTP Datasheet(PDF) 61 Page - Microchip Technology

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