22

Notes on Power-up and the serial port

Reset Circuit

The ADNS-3090 does not perform an internal power up

self-reset. The reset pin must be raised and lowered to

reset the chip. This should be done every time power is

applied. During power-up there will be a period of time

after the power supply is high but before any clocks are

available. The table below shows the state of the various

pins during power-up and reset when the RESET pin is

driven high by a micro-controller.

Power Down Circuit

The following table lists the pin states during power

down.

The chip is put into the power down (PD) mode by

lowering the NPD input. When in PD mode, the oscilla-

tor is stopped but all register contents are retained. To

achieve the lowest current state, all inputs must be held

The chip outputs are driven low or hi-Z during PD to

prevent current consumption by an external load.

LED Drive Mode

The LED has 2 modes of operation: DC and Shutter. In

DC mode it is on at all times the chip is powered except

when in the power down mode via the NPD pin. In

shutter mode the LED is on only during the portion of

the frame that light is required. The LED_MODE bit in the

Configuration_bits register sets the LED mode.

State of Signal Pins After VDD is Valid

Pin

Before Reset

During Reset

After Reset

SPI pullups

Undefined

Off

On (default)

NCS

Hi-Z control functional

Hi-Z control functional

Functional

MISO

Driven or hi-Z

(per NCS)

Driven or hi-Z

(per NCS)

Low or hi-Z

(per NCS)

SCLK

Undefined

Ignored

Functional

MOSI

Undefined

Ignored

Functional

LED_CTRL

Undefined

Low

High

RESET

Functional

High

(externally driven)

Functional

NPD

Undefined

Ignored

Functional

State of Signal Pins During Power Down

Pin

NPD low

After wake from PD

SPI pullups

off

pre-PD state

NCS

hi-Z control functional

functional

MISO

low or hi-Z (per NCS)

pre-PD state or hi-Z

SCLK

ignored

functional

MOSI

ignored

functional

LED_CTRL

low

high

RESET

functional

functional

NPD

low (driven externally)

functional

REFC

REFC

OSC_IN

low

OSC_IN

OSC_OUT

high

OSC_OUT

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PixArt Imaging Inc.

PixArt Imaging Inc.