74hct9046a NXP Semiconductors, 74hct9046a Datasheet - Page 10

• Manufacturer Part Number: 74hct9046a
• Description: Pll With Bandgap Controlled Vco
• Manufacturer: NXP Semiconductors

handbook, full pagewidth
Philips Semiconductors
2003 Oct 30
PLL with band gap controlled VCO
The pulse overlap of the up and down signals (typically 15 ns).
VCO_IN
a. Response with traditional voltage-switch charge-pump
PC2_OUT (74HCT4046A).
(1) Due to parasitic capacitance on PC2_OUT.
(2) Backlash time (dead zone).
Fig.11 The response of a locked-loop in the vicinity of the zero crossing of the phase error.
2.75
2.50
2.25
SIG_IN
UP
DOWN
CURRENT AT
PC2_OUT
PC2_OUT/VCO_IN
PCP_OUT
COMP_IN
VCO_OUT
25
(1)
(2)
0
PC_IN
phase error (ns)
(1)
Fig.10 Timing diagram for PC2.
25
high-impedance OFF-state,
(zero current)
10
VCO_IN
2.75
2.50
2.25
b. Response with current switch charge-pump
PC2_OUT as applied in the 74HCT9046A.
25
0
phase error (ns)
15 ns typical
MBD047
74HCT9046A
Product specification
MBD043
25