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LM98725: SH1 output doesn't toggle during CCD readout. phiA, CP, RS toggle, but look bad

Part Number: LM98725


All signals toggle indefinitely except SH1. There is no "readout window" I can catch on the scope by triggering to SH1. Please help.


I lock the registers (start CCD readout), and watch SH1, PHIA1, PHIB1, CP, RS with scope (high-Z), not loaded at all.

When I toggle "SH1 active" register field on/off in unlocked state, the corresponding output changes DC value from 0 to 3.3V and vice versa.

This means, I look at the proper output. But it doesn't toggle during locked state.

Total current consumption: locked: 124mA, unlocked: 116mA

The registers I touch during configuration:

Signal outputs (5 MHz input clock):

My test circuit based on datasheet circuit:

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