UPD9971 datasheet(38/112 Pages) RENESAS

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µPD9971

Data Sheet S17455EJ2V0DS

5.2 Regulator Block

Figure 5-3 Regulator

Regulator

REGCNT

REGUSE_B

REGOUT

This block has the following functions:

• Generates fixed voltage with the regulator and supplies current to the power supply DVDD pin for digital circuits.

• Requires a short between the regulator output REGOUT pin and the DVDD pin, which must be done at the

outside of the

µPD9971, when the regulator is used.

• Sets the regulator output to the low level when the regulator is not used.

• Receives power supply from REGVDD.

• Requires a supply of 3.0 V power to REGVDD to check that the regulator is not used, even when the regulator is

not used.

This block can be used when the REGUSE_B pin is set to the low level (DGND). When this block is not used, set

the REGUSE_B pin to the high level (EVDD).

While the REGUSE_B pin is set to the low level, this block starts supplying current if the REGCNT pin is set to the

high level, and stops it if the REGCNT pin is set to the low level.

Table 5-1 Setting Of Pins When Regulator Is Used/Is Not Used

Pin Status

When regulator is not used

When regulator is used

REGVDD

3.0 V external power supply

REGOUT

Left open (Output: Low)

Shorted with DVDD

DVDD

Connected to 1.54 V external

power supply

Shorted with REGOUT

High: Regular standby is canceled.

REGCNT

Shorted with DGND

Low: Regular standby

REGUSE_B

Shorted with EVDD

Shorted with DGND

Cautions 1. Be sure to connect a 2.2

µF (± 20 %) capacitor between the REGOUT pin and AGND. Since

capacitors with the above capacitance affect the noise characteristics of the regulator, place

the capacitor as close as possible to the REGOUT pin. Do not connect any other capacitors

to the REGOUT pin.

2. Be sure to connect a 0.1

µF (± 20 %) capacitor between the REGVDD pin and AGND.

3. Note that output may be unstable if a digital block is started before this block is set to the

normal mode.

4. To charge the capacitor connected to the REGOUT pin, about 350 mA of through current

flows into the capacitor for about 50

µs. when the regulator is started. Contact NEC

Electronics if charging causes problems.

UPD9971 Datasheet(PDF) 38 Page - Renesas Technology Corp

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