 |
Datenblatt-Suchmaschine für elektronische Bauteile |
|
|
Datenblatt-Suchmaschine für elektronische Bauteile |
|
ADF4108BCPZ-RL7 Datenblatt(PDF) 9 Page - Analog Devices |
|
||||||||||||||||||||||||||||||
ADF4108BCPZ-RL7 Datenblatt(HTML) 9 Page - Analog Devices |
|
|
9 / 20 page  ADF4108 Rev. 0 | Page 9 of 20 THEORY OF OPERATION REFERENCE INPUT STAGE The reference input stage is shown in Figure 11. SW1 and SW2 are normally closed switches. SW3 is normally open. When power-down is initiated, SW3 is closed and SW1 and SW2 are opened. This ensures that there is no loading of the REFIN pin on power-down. 100kΩ NC REFIN NC NO SW1 SW2 BUFFER SW3 TO R COUNTER POWER-DOWN CONTROL Figure 11. Reference Input Stage RF INPUT STAGE The RF input stage is shown in Figure 12. It is followed by a 2-stage limiting amplifier to generate the CML clock levels needed for the prescaler. 500Ω 1.6V 500Ω AGND RFINA RFINB AVDD BIAS GENERATOR Figure 12. RF Input Stage PRESCALER (P/P + 1) The dual-modulus prescaler (P/P + 1), along with the A and B counters, enables the large division ratio, N, to be realized (N = BP + A). The dual-modulus prescaler, operating at CML levels, takes the clock from the RF input stage and divides it down to a manageable frequency for the CMOS A and B counters. The prescaler is programmable. It can be set in software to 8/9, 16/17, 32/33, or 64/65. It is based on a synchronous 4/5 core. A minimum divide ratio is possible for contiguous output frequencies. This minimum is determined by P, the prescaler value, and is given by: (P2 – P). A AND B COUNTERS The A and B CMOS counters combine with the dual-modulus prescaler to allow a wide ranging division ratio in the PLL feedback counter. The counters are specified to work when the prescaler output is 300 MHz or less. Thus, with an RF input frequency of 4.0 GHz, a prescaler value of 16/17 is valid but a value of 8/9 is not valid. Pulse Swallow Function The A and B counters, in conjunction with the dual-modulus prescaler, make it possible to generate output frequencies that are spaced only by the reference frequency divided by R. The equation for the VCO frequency is as follows: () [] R f A B P f REFIN VCO × + × = where: fVCO is the output frequency of external voltage controlled oscillator (VCO). P is the preset modulus of dual-modulus prescaler (8/9, 16/17, and so on.). B is the preset divide ratio of binary 13-bit counter (3 to 8191). A is the preset divide ratio of binary 6-bit swallow counter (0 to 63). fREFIN is the external reference frequency oscillator. LOAD LOAD FROM RF INPUT STAGE PRESCALER P/P + 1 13-BIT B COUNTER TO PFD 6-BIT A COUNTER N DIVIDER MODULUS CONTROL N = BP + A Figure 13. A and B Counters R COUNTER The 14-bit R counter allows the input reference frequency to be divided down to produce the reference clock to the phase frequency detector (PFD). Division ratios from 1 to 16,383 are allowed. PHASE FREQUENCY DETECTOR AND CHARGE PUMP The phase frequency detector (PFD) takes inputs from the R counter and N counter (N = BP + A) and produces an output proportional to the phase and frequency difference between them. Figure 14 is a simplified schematic. The PFD includes a programmable delay element that controls the width of the antibacklash pulse. This pulse ensures that there is no dead zone in the PFD transfer function and minimizes phase noise and reference spurs. Two bits in the reference counter latch, ABP2 and ABP1, control the width of the pulse. (See Figure 17.) |
Ähnliche Teilenummer - ADF4108BCPZ-RL7 |
|
Ähnliche Beschreibung - ADF4108BCPZ-RL7 |
|
|
|
Link URL |
| Privatsphäre und Datenschutz |
| ALLDATASHEETDE.COM |
| War ALLDATASHEET hilfreich? [ DONATE ] |
Über Alldatasheet | Werbung | Kontakt | Privatsphäre und Datenschutz | Linktausch | Hersteller All Rights Reserved©Alldatasheet.com |
| Russian : Alldatasheetru.com | Korean : Alldatasheet.co.kr | Spanish : Alldatasheet.es | French : Alldatasheet.fr | Italian : Alldatasheetit.com Portuguese : Alldatasheetpt.com | Polish : Alldatasheet.pl | Vietnamese : Alldatasheet.vn Indian : Alldatasheet.in | Mexican : Alldatasheet.com.mx | British : Alldatasheet.co.uk | New Zealand : Alldatasheet.co.nz |
|
Family Site : ic2ic.com |
icmetro.com |
German ▼
English
Chinese
German
Japanese
Russian
Korean
Spanish
French
Italian
Portuguese
Polish
Vietnamese
Indian
Mexican
British
New Zealand
