at85c51snd3 ATMEL Corporation, at85c51snd3 Datasheet - Page 20

• Manufacturer Part Number: at85c51snd3
• Description: At85c51snd3 Single-chip Digital Audio Decoder - Encoder With Usb 2.0 Interface
• Manufacturer: ATMEL Corporation

Schematic
Low Voltage DC-DC in
AT85C51SND3B2
DC-DC Start-Up
DC-DC Shut-Down
DC-DC Connection
20
AT85C51SND3B
Figure 6. Regulator Connection
Note:
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 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 is done by two different ways:
•
•
Note:
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:
DCPWR
DCEN
LVDD
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
Depending on power supply scheme, C
1. If DCEN bit is left set, the DC-DC will restart as soon as the USB power supply
Depending on power supply scheme, C
disappears.
DC-DC
HVDD
Off
VSS
L
Start-Up
DC-DC
DC
C
BVDD
DCLI
BVSS
DCPWR
HV
Firmware
Start-Up
LV
DC1
may replace C
may replace C
RLVDD
RLVDD
CVSS
LVDD
VSS
VSS
DC-DC
DC
On
LV
capacitor (see Figure 8
capacitor (see Figure 6
(1)
.
C
C
DC1
LV
(
(
*
*
)
)
7632D–MP3–01/07
C
DC2
).
).