1.3GHZ DUAL PLL

S1T8825B

5

FUNCTIONAL DESCRIPTIONS

SERIAL DATA INPUT AND TIMING

CK (Pin6), DATA (Pin7), EN (Pin8) terminals in S1T8825B are used for MCU serial data interface (LSB: 1st input

data; MSB: Last input data). Serial data controls the programmable reference divider, programmable divider (CH1),

programmable divider (CH2), and control latch separately by means of group code. Binary serial data is entered via

the DATA pin.

One bit of data is shifted into the internal shift register on the rising edge of the clock. When EN pin is high, stored

data is latched. The three terminals, CK, DATA, and EN, contain Schmitt trigger circuits to keep the data from errors

caused by noise, etc.

< Notice >

1. When power supply of S1T8825B is disconnected, CLK, DATA, EN port from MCU should be pulled low.

2. When power goes up first, R counter data should be entered earlier than N1 and N2 counter data.

3. When power goes up first, control data should be entered earlier than N1 and N2 counter data.

Figure 1.

NOTE: Start data input with LSB first

SERIAL DATA GROUP AND GROUP CODE

The S1T8825B can be controlled through 4 kinds of group selection. Each group is identified by selective a 2-bit

group code given below.

Serial Bits

Group Location

GC1 (MSB)

GC2 (MSB-1)

0

0

Control Latch

0

1

Ch 1 N Latch

1

0

Ch 2 N Latch

1

1

OSC R Latch

≥

≥

≥≥

≥

1us

0.2us

0.2us

0.1us

0.2us

0.1us

0.2us

0.2us

EN

DATA

CK

MSB

N1 (R1)

N2 (R2)

N3 (R3)

N16 (R11)

N17 (R12)

GC2

GC1

LSB

MSB

≥

≥

≥

≥

≥≥

≥

≥

LSB

MSB

LSB