DM368ZCEZ datasheet(84/208 Pages) TI1

84 / 208 page

RTCXI

RTCXO

VSS_32k

Crystal

32.768kHz

1C2

RTCXI

TMS320DM368

SPRS668C

– APRIL 2010 – REVISED JUNE 2011

www.ti.com

6.6.3

PRTCSS Oscillator

The device has an PRTCSS oscillator input/output pair (RTCXI/RTCXO) usable with external crystals or

ceramic resonators to provide clock inputs. The optimal frequency for the crystal is 32.768 kHz. The

electrical requirements and characteristics are described in this section. Figure 6-9 shows an example

circuit.

Figure 6-9. RTCXI1 Oscillator

The load capacitors, C1 and C2, should be chosen such that the equation is satisfied (typical values are

C1 = C2 = 2 fF). CL in the equation below is the load specified by the crystal manufacturer. All discrete

components used to implement the oscillator circuit should be placed as close as possible to the

associated oscillator pins (RTCXI and RTCXO) and to the VSS_32K pin.

(1)

6.6.4

PRTCSS Electrical Data/Timing

Table 6-7. Timing Requirements for RTCXI(1) (2) (see Figure 6-6)

DEVICE

UNIT

NO.

MIN

TYP

MAX

tc(RTCXI)

Cycle time, RTCXI

30.5175

µs

tw(RTCXIH)

Pulse duration, RTCXI high

.45C

.55C

tw(RTCXIL)

Pulse duration, RTCXI low

.45C

.55C

(1)

The reference points for the rise and fall transitions are measured at VIL MAX and VIH MIN.

(2)

C = MXI1/CLKIN1 cycle time in ns. For example, when MXI1/CLKIN1 frequency is 24 MHz use C = 41.6 ns.

Figure 6-10. RTCXI Timing

Peripheral Information and Electrical Specifications

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