ML4044

ML4344_4044 Phase Frequency Detector This device contains two digital phase detectors and a charge pump circuit which converts MTTL inputs to a dc voltage level for use in frequency discrimination and phase–locked–loop applications. The two phase detectors have common inputs. Phase–frequency detector 1 is locked in (indicated by both outputs high) when the negative transitions of the variable input (V1) and reference input (R1) are equal in frequency and phase. If the variable input is lower in frequency or lags in phase, the U1 (up) output goes low; conversely the D1 (down) output goes low when the variable input is higher in frequency or leads the reference input in phase. It is important to note that the duty cycles of the variable input and the reference input are not important since negative transitions control system operation. Phase detector 2, on the other hand, is locked in when the variable input phase lags the reference phase th 90º (indicated by the U2 and D2 outputs alternately going low with equal pulse widths). If the variable input phase lags by more than 90º, U2 will remain low longer than D2, and conversely, if the variable input phase lags the reference phase by less than 90º, D2 remains low longer. In this phase detector the variable input and the reference must have 50% duty cycles. The charge pump accepts the phase detector outputs (U1 or U2 applied to PU, and D1 or D2 applied to PD) and converts them to fixed amplitude positive and negative pulses at the UF and DT outputs respectively. These pulses are applied to a lag-lead active filter, which incorporates external components, as well as the amplifier provided in the MC4344/4044 circuit. The filter provides a dc voltage proportional to the phase error. Page 1 of 5 www.lansdale.com Issue 0 ML4344/4044 LANSDA L E S e m i c o n d u c t o r, Inc. Page 2 of 5 www.lansdale.com Issue 0 ML4344/4044 LANSDA L E S e m i c o n d u c t o r, Inc. Page 3 of 5 www.lansdale.com Issue 0 ML4344/4044 LANSDA L E S e m i c o n d u c t o r, Inc. Page 4 of 5 www.lansdale.com Issue 0 ML4344/4044 LANSDA L E S e m i c o n d u c t o r, Inc. Lansdale Semiconductor reserves the right to make changes without further notice to any products herein to improve reliability, function or design. Lansdale does not assume any liability arising out of the application or use of any product or circuit described herein; neither does it convey any license under its patent rights nor the rights of others. “Typical” parameters which may be provided in Lansdale data sheets and/or specifications can vary in different applications, and actual performance may vary over time. All operating parameters, including “Typicals” must be validated for each customer application by the customer’s technical experts. Lansdale Semiconductor is a registered trademark of Lansdale Semiconductor, Inc. Page 5 of 5 www.lansdale.com Issue 0