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NBC12430FA View Datasheet(PDF) - ON Semiconductor

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NBC12430FA Datasheet PDF : 20 Pages
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NBC12430, NBC12430A
Most of the signals available on the TEST output pin are
useful only for performance verification of the device itself.
However, the PLL bypass mode may be of interest at the
board level for functional debug. When T[2:0] is set to 110,
the device is placed in PLL bypass mode. In this mode the
S_CLOCK input is fed directly into the M and N dividers.
The N divider drives the FOUT differential pair and the M
counter drives the TEST output pin. In this mode the
S_CLOCK input could be used for low speed board level
functional test or debug. Bypassing the PLL and driving
FOUT directly gives the user more control on the test clocks
sent through the clock tree. Figure 7 shows the functional
setup of the PLL bypass mode. Because the S_CLOCK is a
CMOS level the input frequency is limited to 250 MHz or
less. This means the fastest the FOUT pin can be toggled via
the S_CLOCK is 250 MHz as the minimum divide ratio of
the N counter is 1. Note that the M counter output on the
TEST output will not be a 50% duty cycle due to the way the
divider is implemented.
T2
T1
0
0
0
0
0
1
0
1
1
0
1
0
1
1
1
1
T0
TEST (Pin 20)
0
SHIFT REGISTER OUT
1
HIGH
0
FREF
1
M COUNTER OUT
0
FOUT
1
LOW
0
PLL BYPASS
1
FOUT B 4
M[8:0]
ÉÉÉÉ ÉÉÉÉ N[1:0]
ÉÉÉÉ ÉÉÉÉ P_LOAD
VALID
ts
th M, N to P_LOAD
Figure 5. Parallel Interface Timing Diagram
ÇÇÇÇÇÇÇÇ S_CLOCK
C1 C2 C3 C4 C5 C6 C7 C8 C9 C10 C11 C12 C13 C14
S_DATA
ts
th S_DATA to S_CLOCK
T2 T1 T0 N1 N0 M8 M7 M6 M5 M4 M3 M2 M1 M0
S_LÇÇOAÇÇD ÇÇÇÇ
First
Bit
Last
Bit
th
ts
S_CLOCK to S_LOAD Figure 6. Serial Interface Timing Diagram
FREF_EXT
MCNT PLL 12430
SCLOCK
VCO_CLK
0
NB
FOUT
1
(1, 2, 4, 8) (VIA ENABLE GATE)
SDATA
M COUNTER
FDIV4
MCNT
7
DECODE
LOW
FOUT
MCNT
TEST
MUX
SHIFT
REG T0
FREF
HIGH
0
14- BIT T1
T2
LATCH
Reset
SLOAD
ăT2=T1=1, T0=0: Test Mode PLOAD
ăSCLOCK is selected, MCNT is on TEST output, SCLOCK B N is on FOUT pin.
PLOAD acts as reset for test pin latch. When latch reset, T2 data is shifted out TEST pin.
Figure 7. Serial Test Clock Block Diagram
TEST
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