Atmel AT85DVK-07 Especificaciones descargar pdf (Pagina 19)

AT85C51SND3Bx

7632A–MP3–03/06

Schematic Figure 6. Regulator Connection

Note: Depending on power supply scheme, C

may replace C

capacitor (see Figure 8).

Low Voltage DC-DC in

AT85C51SND3B3

The low voltage output DC-DC converter supplies power to the internal device and

external devices through LVDD power pin. It operates from a single AAA battery. Its

nominal voltage output is 1.8V.

DC-DC Start-Up DC-DC start-up is done by asserting the DCPWR input until the voltage reaches its

nominal value (see

Section “Power Fail Detector”) and firmware starts execution and

sets the DCEN bit in PCON to maintain the DC-DC enabled. DCPWR input can then be

released. As shown in

Figure 8 DCPWR input is asserted by pressing a key connected

to BVSS.

Figure 7. DC-DC Start-Up Phase

DC-DC Shut-Down DC-DC shut-down is done by two different ways:

• Clearing the DCEN bit while DCPWR pin is de-asserted

• Detecting the presence of an internal or external 3V supply, e.g. when the device is

connected to USB, DC-DC is disabled to save battery power

(1)

Note: 1. If DCEN bit is left set, the DC-DC will restart as soon as the USB power supply

disappears.

DC-DC Connection Figure 8 shows how to connect external components, inductance and components

value along with power characteristics are specified in the section “DC characteristics”.

Figure 8. Battery DC-DC Connection

Note: Depending on power supply scheme, C

DC1

may replace C

capacitor (see Figure 6).

HVDD

VSS

RLVDD

(

)

VSS

DCPWR

DCEN

DC-DC

Start-Up

LVDD

Firmware

Start-Up

DC-DC

Off

LVDD

BVDD

BVSS

Battery

DCLI

DC1

(

)

VSS

RLVDD

CVSS

DC2

DCPWR

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