www.ti.com

DETAILED DESCRIPTION OF OUTPUT CONFIGURATIONS

Output Configuration A

Output Configuration B

CDC2536

SCAS377E – APRIL 1994 – REVISED JULY 2004

Because it is based on PLL circuitry, the CDC2536 requires a stabilization time to achieve phase lock of the

feedback signal to the reference signal. This stabilization time is required following power up and application of a

fixed-frequency, fixed-phase signal at CLKIN, as well as following any changes to the PLL reference or feedback

signals. Such changes occur upon change of SEL, enabling the PLL via TEST, and upon enable of all outputs

via OE.

The CDC2536 is characterized for operation from 0

°C to 70°C.

The voltage-controlled oscillator (VCO) used in the CDC2536 has a frequency range of 100 MHz to 200 MHz,

twice the operating frequency of the CDC2536 outputs. The output of the VCO is divided by two and by four to

provide reference frequencies with a 50% duty cycle of one-half and one-fourth the VCO frequency. SEL

determines which of the two signals is buffered to each bank of device outputs.

One device output must be externally wired to FBIN to complete the PLL. The VCO operates such that the

frequency of the output matches that of CLKIN. In the case that a VCO/2 output is wired to FBIN, the VCO must

operate at twice the CLKIN frequency resulting in device outputs that operate at either the same or one-half the

CLKIN frequency. If a VCO/4 output is wired to FBIN, the device outputs operate at the same or twice the CLKIN

frequency.

Output configuration A is valid when any output configured as a 1

× frequency output in Table 1 is fed back to

FBIN. The input frequency range for CLKIN is 50 MHz to 100 MHz when using output configuration A. Outputs

configured as 1/2

× outputs operate at half the CLKIN frequency, while outputs configured as 1× outputs operate

at the same frequency as CLKIN.

Table 1. Output Configuration A

INPUT

OUTPUTS

1/2

×

1

×

SEL

FREQUENCY

FREQUENCY

L

None

All

H

1Yn

2Yn

Output configuration B is valid when any output configured as a 1

× frequency output in Table 2 is fed back to

FBIN. The input frequency range for CLKIN is 25 MHz to 50 MHz when using output configuration B. Outputs

configured as 1

× outputs operate at the CLKIN frequency, while outputs configured as 2× outputs operate at

double the frequency of CLKIN.

Table 2. Output Configuration B

INPUT

OUTPUTS

1

×

2

×

SEL

FREQUENCY

FREQUENCY

H

1Yn

2Yn

L

All

None

2