UM10208_2
© NXP B.V. 2007. All rights reserved.
User manual
Rev. 02 — 1 June 2007
46 of 362
NXP Semiconductors
UM10208
Chapter 6: LPC2800 DC-DC converter
A positive edge on the STOP signal causes the DC-DC converter to shut off and the
internal reset to be asserted.
Remark:
The change in voltage level on the START signal is due to the connection of this
signal in the application. See
, which shows how battery voltage and
DCDC_V
DDO(3V3)
are combined for use with START and STOP switches.
3.2 START and STOP from USB power
shows the timing of the DC-DC Converter while USB power is applied and
removed. Note that timing and voltage levels are not to scale.
Application of USB power when the device is not operating causes an automatic start-up.
The internal reset remains asserted for about 1 ms after power becomes available from
the DC-DC Converter. Removing USB power causes an automatic STOP.
Fig 12. START and STOP of the internal DC-DC converter when battery powered
DC-DC
enable
START
DCDC_V
DDO(3v3)
STOP
(internal
reset_n)
Supply_OK
~1ms
DCDC_V
BAT