HMC701LP6CE Datasheet, PDF (28/46 Pages) Hittite Microwave Corporation – 8 GHz 16-Bit Fractional-N Synthesizer

v03.0709
HMC701LP6CE
8 GHz 16-Bit Fractional-N Synthesizer
Soft Reset
The SPI registers may also be soft reset by an SPI write to strobe global_swrst_regs (Reg00h<0> Table 11).
All other digital, including the fractional modulator, may be reset with an SPI write to strobe global_swrst_dig
(Reg00h<1> Table 11).
Hardware Reset
The SPI registers may also be hardware reset by holding RSTB, pin 19, low.
Power Down
The HMC701LP6CE may be powered down by writing a zero to Reg01h Table 12. In power down state the
HMC701LP6CE should draw less than 10uA. It should be noted that Reg01h is the Enable and Reset Register which
controls 16 separate functions in the chip. Depending upon the desired mode of operation of the chip, not all of the
functions may be enabled when in operation. Hence power up of the chip requires a selective write to Reg01 bits.
An easy way to return the chip to its prior state after a power down is to first read Reg01h and save the state, then
write a zero to Reg01h for reset and then simply rewrite the previous value to restore the chip to the desired operating
mode.
CW Sweeper Mode
The HMC701LP6CE features a built in frequency sweeper function. This function supports external or automatic
triggered sweeps.
Sweeper Modes include:
a. 2-Way Sweep Mode: alternating positive and negative frequency ramps.
b. 1-Way Sweep Mode
c. Single Step Ramp Mode
Applications include test instrumentation, FMCW sensors, automotive radars and others. The parameters of the
sweep function are illustrated in Figure 26.
The sweep generator is enabled with ramp_enable in (Reg14h<1> Table 30). The sweep function cycles through a
series of discrete frequency values, which may be
a. Stepped by an automatic sequencer, or
b. Single stepped by individual triggers in Single Step Mode.
Triggering of each sweep, or step, may be configured to operate:
a. Via a serial port write to Reg14h<2> ramp_trigg (if Reg 14h<2> = 0 )
b. Automatically generated internally,
c. Triggered via TTL input on GPO3 Reg14h<5> = 1.
Sweep parameters are set as follows:
Initial Frequency, f_o = Current frequency value of the synthesizer, (EQ 15)
Final Frequency, f_f = Frequency of the synthesizer at the end of the ramp
The frequency step size while ramping is controlled by rampstep, (Reg15h Table 31).
Frequency Step Size ∆ƒ_step = rampstep • fatal / 2²⁴ • R
where R is the value of the reference divider (rfp_div_ratio in Table 14)
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