TPS610985: Large current draw during startup.

I have designed an RF energy harvesting circuit which uses the TPS610985. The rectifier device supplying the input voltage to VIN can supply a maximum voltage of approximately 1.2 V, and a maximum current of approximately 1 mA.

I have prototyped the design and found that the TPS610985 will not fully turn on with this device as its supply. I am basically observing the behavior described in the datasheet as follows:

" If the input voltage is not high enough, a low voltage startup oscillator operates the switches first. During this phase, the switching frequency is controlled by the oscillator, and the maximum switch current is limited. Once the converter has built up the output voltage V(MAIN) to approximately 1.8 V, the device switches to the normal hysteretic current mode operation and the VMAIN rail starts to supply the internal control circuit. If the input voltage is too low or the load during startup is too heavy, which makes the converter unable to build up 1.8 V at V(MAIN) rail, the boost converter can't start up successfully. It will keep in this status until the input voltage is increased or removed. "

When I replaced the rectifier with a DC power supply to test the circuit, I have found that the TPS610985 will draw up to 16.5 mA while the low voltage startup oscillator is operating the switches (measured VIN=750 mV, VMAIN = 1.77 V, ISUPPLY=16.5 mA, MODE= 0 V ).

Is this behavior normal? VMAIN on the boost converter is very lightly loaded and once it enters the normal hysteretic current mode the whole circuit only draws 20 uA from the DC supply (with VIN = 1 V).

I have the recommended inductor (4.7 uH) and capacitors connected to the TPS610985 as described in the datasheet (as well as the 400 Ohm resistor and filter cap on the input), and it works very well once in the hysteretic current mode - this high current draw during startup was unexpected.