SMJ320C26B Datasheet, PDF (21/40 Pages) Texas Instruments – DIGITAL SIGNAL PROCESSOR

SMJ320C26
DIGITAL SIGNAL PROCESSOR
SGUS 016A – AUGUST 1990 – REVISED AUGUST 2001
CLOCK CHARACTERISTICS AND TIMING
The SMJ320C26 can use either its internal oscillator or an external frequency source for a clock.
internal clock option
The internal oscillator is enabled by connecting a crystal across X1 and X2/CLKIN (see Figure 2). The frequency
of CLKOUT1 is one-fourth the crystal fundamental frequency. The crystal should be either fundamental or
overtone mode, and parallel resonant, with an effective series resistance of 30 Ω, a power dissipation of
1 mW, and be specified at a load capacitance of 20 pF. Note that overtone crystals require an additional tuned
LC circuit (see the application report, Hardware Interfacing to the TMS320C25).
PARAMETER
fx Input clock frequency^†
C1, C2
† _{This parameter is not production tested.}
TEST CONDITIONS
TA = –55°C MIN
TC = 125°C MAX
MIN TYP MAX UNIT
6.7
40.0 MHz
10
pF
X1
X2/CLKIN
CRYSTAL
C1
C2
Figure 1. Internal Clock Option
external clock option
An external frequency source can be used by injecting the frequency directly into X2/CLKIN with X1 left
unconnected. The external frequency injected must conform to the specifications listed in the table below.
switching characteristics over recommended operating conditions (see Note 1)
PARAMETER
MIN TYP^† MAX
tc(C)
CLKOUT1/CLKOUT2 cycle time
td(CIH-C) CLKIN high to CLKOUT1/CLKOUT2/STRB high/low
tf(C)
CLKOUT1/CLKOUT2/STRB fall time
tr(C)
CLKOUT1/CLKOUT2/STRB rise time
tw(CL)
CLKOUT1/CLKOUT2 low pulse duration
tw(CH)
CLKOUT1/CLKOUT2 high pulse duration
td(C1-C2) CLKOUT1 high to CLKOUT2 low, CLKOUT2 high to CLKOUT1 high, etc.
† _{This parameter is not production tested.}
NOTE 1: Q = 1/4tc(C)
100
5
2Q–8
2Q–8
Q–6
600
32
5
5
2Q 2Q+8
2Q 2Q+8
Q Q+6
UNIT
ns
ns
ns
ns
ns
ns
ns
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