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Atmel Electronic Components Datasheet



U2781B

Frequency Synthesizer



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U2781B pdf
Frequency Synthesizer
U2781B
Description
The programmable frequency synthesizer IC U2781B for
µP-controlled applications is realized with Atmel
Wireless & Microcontrollers’ advanced UHF process
which is very suitable for combinations of fast ECL logic
and low-current I2L logic. The benefits are high input
sensitivity combined with low power consumption and
therefore small packages (SSO20). This makes the
device a perfect choice for cordless phones and handheld
cellular radio sets up to 1.1 GHz.
Electrostatic sensitive device.
Observe precautions for handling.
Features
D Very low current consumption (typ. 3 V/ 5 mA)
D Supply-voltage range: 2.7 to 5.5 V
D Max. input frequency: 1.1 GHz
D Programmable prescaler 64/ 65 or 128/ 129
D Controlled by 3-wire bus with fclock up to 500 kHz
D Status output for PLL lock/ unlock condition
D Very fast phase detector
D SSO20 package
D ESD protection in accordance with MIL-STD. 883
method 3015 class 2
Benefits
D Very low current consumption extends talk time
D Few external components and SSO package save costs
and space
Block Diagram
Osci
Osco
VS
GND
Clock
Data
Enable
1
3
5
7
11
13
14
Oscillator
1-bit latch
load control
RFi
10
Prescaler
64/65
128/129
14-bit
reference counter
15-bit latch
18-bit
shift register
18-bit latch
7-bit
swallow
counter
11-bit
main
counter
Phase
detector
Charge
pump
Mo
17
LDo
8
VSCP
4
CP
6
15 PS
U2781B
Figure 1. Block diagram
Rev. A4, 11-Sep-00
1 (10)



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U2781B pdf
U2781B
Ordering Information
Extended Type Number
U2781B-MFS
U2781B-MFSG3
SS020
SS020
Package
Remarks
Tube, MOQ 830 pcs
Taped and reeled, MOQ 4000 pcs
Functional Description
The IC is controlled by a 3-wire bus with Clock, Data and
Enable inputs for programming the scaling factors of the
programmable counter, the reference counter and the
prescaler.
A TCXO can be connected to the oscillator input (OSCi)
as an alternative solution to the common crystal reference
oscillator. In that case, the oscillator output (OSCo)
should be left open.
The charge-pump output operates as switched current
sources. The characteristics of the phase-locked loop can
be determinated by the external lowpass filter.
The phase characteristic of the phase detector is convert-
ible and thus matchable to different frequency/ tuning
voltage characteristics.
Pin Description
Pin Symbol
Function
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ1 Osci Oscillator input
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ2 n.c. Not connected
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ3 Osco Oscillator output
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ4 VSCP Charge-pump supply voltage
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ5 Vs Supply voltage
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ6 CP Charge-pump output
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ7 GND Ground
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ8 LDo Lock-detector output
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ9 n.c. Not connected
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ10 RFi VCO input
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ11 Clock 3-wire bus Clock
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ12 n.c. Not connected
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ13 Data 3-wire bus Data
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ14 Enable 3-wire bus Enable
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ15 PS Phase select input
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ16 n.c. Not connected
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ17 Mo Monitor output for fp and fr
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ18 n.c. Not connected
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ19 n.c. Not connected
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ20 n.c. Not connected
Osci 1
n.c. 2
Osco 3
VSCP 4
VS 5
CP 6
GND 7
LDo 8
n.c. 9
RFi 10
U2781B
20 n.c.
19 n.c.
18 n.c.
17 Mo
16 n.c.
15 PS
14 Enable
13 Data
12 n.c.
11 Clock
Figure 2. Pinning SSO20
2 (10)
Rev. A4, 11-Sep-00



Part Number U2781B
Description Frequency Synthesizer
Maker Atmel - Atmel
Total Page 10 Pages
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