ADSP-21469 View Datasheet(PDF) - Analog Devices
Part Name
Description
MFG CO.
'ADSP-21469' PDF : 56 Pages View PDF
ADSP-21467/ADSP-21469
Clock Input
Table 19. Clock Input
400 MHz1
Parameter
Min
Max
Timing Requirements
tCK
CLKIN Period
tCKL
CLKIN Width Low
tCKH
CLKIN Width High
tCKRF
tCCLK5
fVCO6
tCKJ7, 8
CLKIN Rise/Fall (0.4 V to 2.0 V)
CCLK Period
VCO Frequency
CLKIN Jitter Tolerance
153
7.5
7.5
2.5
200
–250
100
45
45
34
10
900
+250
1 Applies to all 400 MHz models. See Ordering Guide on Page 74.
2 Applies to all 450 MHz models. See Ordering Guide on Page 74.
3 Applies only for CLK_CFG1–0 = 00 and default values for PLL control bits in PMCTL.
4 Guaranteed by simulation but not tested on silicon.
5 Any changes to PLL control bits in the PMCTL register must meet core clock timing specification tCCLK.
6 See Figure 5 on Page 24 for VCO diagram.
7 Actual input jitter should be combined with ac specifications for accurate timing analysis.
8 Jitter specification is maximum peak-to-peak time interval error (TIE) jitter.
450 MHz2
Min
Max
13.26
6.63
6.63
2.22
200
–250
100
45
45
34
10
900
+250
CLKIN
tCKH
tCK
tCKL
tCKJ
Figure 7. Clock Input
Clock Signals
The processor can use an external clock or a crystal. See the
CLKIN pin description in Table 10. Programs can configure the
processor to use its internal clock generator by connecting the
necessary components to CLKIN and XTAL. Figure 8 shows the
component connections used for a crystal operating in funda-
mental mode. Note that the clock rate is achieved using a
25 MHz crystal and a PLL multiplier ratio 16:1 (CCLK:CLKIN
achieves a clock speed of 400 MHz).
To achieve the full core clock rate, programs need to configure
the multiplier bits in the PMCTL register.
CLKIN
C1
22pF
ADSP-2146x
R1
1M: *
Y1
25.000 MHz
XTAL
R2
47: *
C2
22pF
*TYPICAL VALUES
CHOOSE C1 AND C2 BASED ON THE CRYSTAL Y1.
CHOOSE R2 TO LIMIT CRYSTAL DRIVE POWER.
REFER TO CRYSTAL MANUFACTURER'S
SPECIFICATIONS.
Figure 8. Recommended Circuit for
Fundamental Mode Crystal Operation
Unit
ns
ns
ns
ns
ns
MHz
ps
Rev. B | Page 26 of 76 | March 2013
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