Data Sheet ADF4108
Rev. E | Page 7 of 20
PIN CONFIGURATION AND FUNCTION DESCRIPTIONS
06015-003
19
R
SET
20
CP
18
V
P
17
DV
DD
16
DV
DD
ADF4108
15 MUXOUT
14 LE
13 DATA
12 CLK
11 CE
PGND 1
AGND 2
AGND 3
RF
IN
B 4
RF
IN
A 5
TOP VIEW
(Not to Scale)
6
7
8
DGND 9
DGND 10
AV
DD
AV
DD
REF
IN
NOTES
1. THE EXPOSED PAD MUST BE
CONNECTED TO AGND.
Figure 3. Pin Configuration
Table 4. Pin Function Descriptions
Pin No. Mnemonic Description
1 CPGND Charge Pump Ground. This is the ground return path for the charge pump.
2, 3 AGND Analog Ground. This is the ground return path of the prescaler.
4 RF
IN
B
Complementary Input to the RF Prescaler. This point must be decoupled to the ground plane with a small bypass
capacitor, typically 100 pF. See Figure 11.
5 RF
IN
A Input to the RF Prescaler. This small signal input is ac-coupled to the external VCO.
6, 7 AV
DD
Analog Power Supply. This voltage may range from 3.2 V to 3.6 V. Decoupling capacitors to the analog ground
plane should be placed as close as possible to this pin. AV
DD
must be the same value as DV
DD
.
8 REF
IN
Reference Input. This is a CMOS input with a nominal threshold of V
DD
/2 and a dc equivalent input resistance of
100 kΩ. See Figure 10. This input can be driven from a TTL or CMOS crystal oscillator or it can be ac-coupled.
9, 10 DGND Digital Ground.
11 CE
Chip Enable. A logic low on this pin powers down the device and puts the charge pump output into three-state
mode. Taking the pin high powers up the device, depending on the status of the power-down bit, F2.
12 CLK
Serial Clock Input. This serial clock is used to clock in the serial data to the registers. The data is latched into the
24-bit shift register on the CLK rising edge. This input is a high impedance CMOS input.
13 DATA
Serial Data Input. The serial data is loaded MSB first with the 2 LSBs being the control bits. This input is a high
impedance CMOS input.
14 LE
Load Enable, CMOS Input. When LE goes high, the data stored in the shift registers is loaded into one of the four
latches, the latch being selected using the control bits.
15 MUXOUT
This multiplexer output allows either the lock detect, the scaled RF, or the scaled reference frequency to be
accessed externally.
16, 17 DV
DD
Digital Power Supply. This may range from 3.2 V to 3.6 V. Decoupling capacitors to the digital ground plane should
be placed as close as possible to this pin. DV
DD
must be the same value as AV
DD
.
18 V
P
Charge Pump Power Supply. This voltage should be greater than or equal to V
DD
. In systems where V
DD
is 3.3 V, it
can be set to 5 V and used to drive a VCO with a tuning range of up to 5 V.
19 R
SET
Connecting a resistor between this pin and CPGND sets the maximum charge pump output current. The nominal
voltage potential at the R
SET
pin is 0.66 V. The relationship between I
CP
and R
SET
is
SET
MAXCP
R
I
25.5
with R
SET
= 5.1 kΩ, I
CP MAX
= 5 mA.
20 CP
Charge Pump Output. When enabled, this pin provides ±I
CP
to the external loop filter, which in turn drives the
external VCO.
EP Exposed Pad. The exposed pad must be connected to AGND.
