Datasheet

OR
OR
32kHz
32KXIN
32KXOUT
32-kHz
OSC
IO_1P8
(1.8V)
32KCLKOUT
RTC
032-072
TPS65950
www.ti.com SWCS032E–OCTOBER 2008–REVISED JANUARY 2011
Figure 12-11. 32.768-kHz Clock Output Block Diagram
The TPS65950 has an internal 32.768-kHz oscillator connected to an external 32.768-kHz crystal through
the 32KXIN/32KXOUT balls or an external digital 32.768-kHz clock through the 32KXIN input (see
Figure 12-11). The TPS65950 also generates a 32.768-kHz digital clock through the 32KCLKOUT pin and
can broadcast it externally to the application processor or any other devices. The 32KCLKOUT clock is
broadcast by default in the TPS65950 active mode, but can be disabled if it is not used.
The 32.768-kHz clock (or signal) also clocks the RTC embedded in the TPS65950. The RTC is not
enabled by default. The host processor must set the correct date and time and enable the RTC.
The 32KCLKOUT output buffer can drive several devices (up to a 40-pF load). At startup, the 32.768-kHz
output clock (32KCLKOUT) must be stabilized (frequency/duty cycle) before the signal output. Depending
on the startup condition, this can delay the startup sequence.
Table 12-9 lists the electrical characteristics of the 32KCLKOUT output clock.
Table 12-9. 32KCLKOUT Output Clock Electrical Characteristics
Name Parameter Description Min Typ Max Unit
f Frequency 32.768 kHz
C
L
Load capacitance 40 pF
V
OUT
Output clock voltage, depending on output reference level IO_1P8 (see Section 2) 1.8
(1)
V
V
OH
Voltage output high V
OUT
– 0.45 V
OUT
V
V
OL
Voltage output low 0 0.45 V
(1) The output voltage depends on output reference level, which is IO_1P8 (see Section 2, Terminal Description).
Table 12-10 lists the timing characteristics of the 32KCLKOUT output clock. Figure 12-12 shows the
waveform of the 32KCLKOUT output clock.
Table 12-10. 32KCLKOUT Output Clock Switching Characteristics
Name Parameter Description Min Typ Max Unit
CK0 1/t
C(32KCLKOUT)
Frequency 32.768 MHz
CK1 t
W(32KCLKOUT)
Pulse duration, 32KCLKOUT low or high 0.40*t
C(32KCLKOUT)
0.60*t
C(32KCLKOUT)
ns
Copyright © 2008–2011, Texas Instruments Incorporated Clock Specifications 141
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