MC145181FTAR2

**The MC145181 is a dual frequency synthesizer containing very–low supply

voltage circuitry. The device supports two independent loops with a single input reference and operates down to 1.8 V. Phase noise reduction circuitry is incorporated into the device.**

The MC145181 operates up to 550 MHz on the main loop and up to 60 MHz on the secondary loop. The device has a 32/33 prescaler for the main loop. Lock detection circuitry for both loops is multiplexed to a single output.
Two 8–bit DACs are powered through a dedicated pin. The DAC supply range is 1.8 to 3.6 V; this voltage may differ from the main supply.

• Operating Frequency

Main Loop: 100 to 550 MHz
Secondary Loop: 10 to 60 MHz
• Operating Supply Voltage: 1.8 to 3.6 V
• Nominal Supply Current, Both Loops Active: 3 mA
• Maximum Standby Current, All Systems Shut Down: 10 µA
• Phase Detector Output Current:
1.8 V Supply — PDout–Hi: 2.8 mA, PDout–Lo: 0.7 mA
≥2.5 V Supply — PDout–Hi: 4.4 mA, PDout–Lo: 1.1 mA
• Two Independent 8–Bit DACs with Separate Supply Pin (Up to 3.6 V)
• Lock Detect Output with Adjustable Lock Indication Window
• Independent R Counters Allow Independent Step Sizes for Each Loop
• Main Loop Divider Range: 992 to 262,143
• Secondary Loop Divider Range: 7 to 8,191
• Fractional Reference Counters Divider Range: 20 to 32,767.5
• Auxiliary Reference Divider with Small–Signal Differential
Output — Ratios: 8, 10, 12.5
• Three General–Purpose Outputs
• Direct Interface to Motorola SPI Data Port Up to 10 Mbps