UM10208_2
© NXP B.V. 2007. All rights reserved.
User manual
Rev. 02 — 1 June 2007
48 of 362
NXP Semiconductors
UM10208
Chapter 6: LPC2800 DC-DC converter
4.
DC-DC registers
The DC-DC Converter block includes 3 registers. Two allow fine adjustment of the output
voltages of the DC-DC converters (not the LDO regulator outputs). The third allows
switching the DC-DC Converter clock from the internal Ring Oscillator to 12 MHz from the
CGU. The registers are shown in
Fig 14. Change from battery to USB supply and off
STOP
DCDC_V
USB
DCDC_V
BAT
START
* DC-DC output voltage may vary during the change from DC-DC output to LDO output.
(internal
reset_n)
Supply_OK
DC-DC
enable
** Between Stop and Start, the device is in the idle mode, supplies DCDC_V
DDO(3V3)
and
DCDC_V
DDO(1V8)
are present, but only a small current is required.
**
*
DCDC_V
DDO(1V8)
and
DCDC_V
DDO(3v3)
Table 26.
DC-DC converter registers
Name
Size
Description
Access
Reset value
Address
DCDCADJUST1
3
Output voltage adjustment value for DCDC
converter 1 (3.3 V supply)
R/W
0x3
0x8000 5004
DCDCADJUST2
3
Output voltage adjustment value for DCDC
converter 2 (1.8 V supply)
R/W
0x1
0x8000 5008
DCDCCLKSEL
1
Clock selection for DC-DC converters
R/W
0
0x8000 500C