MCIMX233CJM4B Datasheet, PDF (1296/1612 Pages) Freescale Semiconductor, Inc – i.MX23 Applications Processor Reference Manual

Power Supply
Table 32-5. HW_POWER_5VCTRL Bit Field Descriptions
BITS
LABEL
10:8 VBUSVALID_TRSH
7
PWDN_5VBRNOUT
6
ENABLE_LINREG_ILIMIT
5
DCDC_XFER
4
VBUSVALID_5VDETECT
3
VBUSVALID_TO_B
2
ILIMIT_EQ_ZERO
RW RESET
RW 0x0
RW 0x1
RW 0x0
RW 0x0
RW 0x0
RW 0x0
RW 0x0
DEFINITION
Set the threshold for the VBUSVALID comparator. This
comparator is the most accurate method to determine
the presence of 5v, and includes hystersis to minimize
the need for software debounce of the detection. This
comparator has ~50mV of hystersis to prevent
chattering at the comparator trip point.
000: 2.9V
001: 4.0V
010: 4.1V
011: 4.2V
100= 4.3V
101: 4.4V
110: 4.5V
111: 4.6V
The purpose of this bit is to power down the device if
5V is removed before the system is completely
initialized. Clear this bit to disable automatic hardware
powerdown AFTER the system is configured for 5v
removal. This bit should not be set if DCDC_XFER is
set.
Enable the current limit in the linear regulators. The
current limit is active during powerup from 5v and
automatically disables before the ROM executes. This
limit is needed to meet the USB in rush current
specification of 100mA + 50uC. Note this linear
regulator current limit is not related to the
CHARGE_4P2_ILIMIT.
Enable automatic transition to switching DC-DC
converter when VDD5V is removed. The LRADC must
be operational and the BATT_VAL field must be written
with the battery voltage using 8-mV step-size. It is also
important to set the EN_BATADJ field.
Power up and use VBUSVALID comparator as
detection circuit for 5V in the switching converter.
Default is for the switching converter to use the
VDD5V_GT_VDDIO status bit to determine the
presence of 5V in the system. The VBUSVALID
comparator provides a more accurate and adjustable
threshold to determine the presence of 5V in the
system, and is the recommended method of detecting
5V.
This bit muxes the Bvalid comparator to the
VBUSVALID comparator and is used for test purposes
only.
The amount of current the device will consume from
the 5V rail is minimized. The VDDIO linear regulator
current limit is set to zero mA. Also, the source of
current for the crystal oscillator and RTC is switched to
the battery. Note that this functionality does not affect
battery charge.
32-22
i.MX23 Applications Processor Reference Manual, Rev. 1
Preliminary—Subject to Change Without Notice
Freescale Semiconductor