Datasheet
t =2
(reset)
x128x
(1V-0.25V)xC
(reset)
2 Am
()
TPS65022
SLVS667A –JULY 2006– REVISED SEPTEMBER 2011
www.ti.com
VRTC Output
The VRTC output is typically connected to the Vcc_Batt pin of a Intel® PXA270 processor. During power-up of
the processor, the TPS65022 internally switches from the LDO or the backup battery to the system voltage
connected at the VSYSIN pin (see Figure 25).It is required that a 4.7-μF (minimum) capacitor be added to the
VRTC pin even if the output is not used.
LDO1 and LDO2
The LDOs in the TPS65022 are general-purpose LDOs which are stable using ceramics capacitors. The
minimum output capacitor required is 2.2 μF. The LDOs output voltage can be changed to different voltages
between 1 V and 3.3 V using the I
2
C interface. Therefore, they can also be used as general-purpose LDOs in
applications powering processors different from PXA270. The supply voltage for the LDOs needs to be
connected to the VINLDO pin, giving the flexibility to connect the lowest voltage available in the system and
provides the highest efficiency.
TRESPWRON
This is the input to a capacitor that defines the reset delay time after the voltage at VRTC rises above 2.52 V.
The timing is generated by charging and discharging the capacitor with a current of 2 μA between a threshold of
0.25 V and 1 V for 128 cycles. A 1-nF capacitor gives a delay time of 100 ms.
While there is no real upper and lower limit for the capacitor connected to TRESPWRON, it is recommended to
not leave signal pins open.
(9)
Where:
t
(reset)
is the reset delay time
C
(reset)
is the capacitor connected to the TRESPWRON pin
The minimum and maximum values for the timing parameters called ICONST (2 µA), TRESPWRON_UPTH (1 V)
and TRESPWRON_LOWTH (0.25 V) can be found under the electrical characteristics.
V
CC
-Filter
An RC filter connected at the VCC input is used to keep noise from the internal supply for the bandgap and other
analog circuitry. A typical value of 10 R and 1 μF is used to filter the switching spikes, generated by the dc-dc
converters. A larger resistor than 10 R should not be used because the current into V
CC
of up to 3 mA causes a
voltage drop at the resistor causing the undervoltage lockout circuitry connected at V
CC
internally to switch off too
early.
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