Apple Webcam – part 2

Apple Web Cam Camera Board6846 6257

On the back of the camera board is a small 14 pin ic labeled 6846 6257. The ICX098 datasheet indicates the CCD requires a 15V 6mA supply. So I speculate that this is a boost regulator to supply the 15V to the CCD.


It is a small (2.87mm x 1.43mm) but extremely pretty die – with die mark A245 and BB (Which I don’t think is for Burr-Brown in this case).

6846 6257 die photo

I love how it is totally symmetrical apart from the small region in the centre-top of the die. It looks like a voltage regulator to me, with the large output transistors at either end.

It is fabricated with a two metal (Aluminum) analog process.  There are several different transistor layouts used here are a few high resolution images (Imaged with my 20x objective)

Here are some rectangular layout bipolar transistors

And last you can see two different resistor types (values) are used (The blue diffusion, and pink diffusion resistors)

Sony D2450R

Moving on to the main board lets look at the other Sony branded chip.  I found a datasheet which describes the chip as “a timing generator IC which generates the timing pulses for performing progressive scan readout for digital still camera and personal computer image input applications using the ICX098AK CCD image sensor.  The chip has a built-in vertical driver.”

Die marks show this was designed in 1997 so it had been around a few years before use in this webcam application.




The die (3.85mm x 3.85mm) is a good one to look at with some interesting features revealed in the microscope.Sony D2450R die photo

Very conveniently (And most unusual) Sony have numbered the bond pads which when you study the die with the datasheet helps a lot. At the top of die connected to pads 40-46 is the vertical driver.  This block  consists of several large (Multi-fingered) CMOS transistors. This is a closer view of one part (Taken with my 20x objective)

Each gate is 1.5μm long x 50μm wide and 24 fingers for the smaller one (i.e. 1.5μm long x 1200μm wide) I guess is NMOS. And the large transistor has 36 x 100μm wide gates so 3x larger and presumably PMOS so as to have equivalent drive currents.

The digital section is also interesting.  You can see in the die photo it is not very dense. Looking closer (With 80x objective) you can see it is actually a pre-defined set of gates wired up with the 3 levels of metal, a primitive gate array. I believe the process is 0.8μm CMOS as the smallest gates measure (To the best of my ability ~0.8μm)


Unless this base chip is used in a range of other CCD drivers (Possible) it is a strange way of producing digital logic.  The die could be a lot smaller (And therefore cheaper) there are whole areas where the base transistors are not used. Such as down the sides of the driver section.  This is the left side.















There are also 16 identical custom layout blocks around the edge. I don’t know what they are, but based on the datasheet I speculate they may be frequency divider, and shift registers.


This is a close up (80x obj) from one of these


We have looked at the CCD, its voltage regulator and timing generator now lets look at one more device. The output of the CCD goes into a TLV990 a “10bit, 21Msps Area CCD Analog Front End.”  The TLV990-21 performs all the analog-processing functions necessary to maximize the dynamic range, corrects various errors associated with the CCD sensor, and then digitizes the results with an on-chip high-speed analog-to-digital converter (ADC).

Designed by TI in 1999

And made in quite an advanced CMOS process (Likely 0.13nm).  The die photo is aesthetically interesting

TI TLV990 die photo

I can’t identify the blocks, but I think the structure in the bottom right is a pipeline ADC, and the four blocks in the bottom left are DAC’s. There are four digital to analog converters (For black level and offset calibration, internal reference voltage, and external system control). Also on this chip is an input clamp circuit for CCD signal, a correlated double sampler (CDS), a 0-36dB range programable gain amplifier (PGA) and both parallel data port and a serial port interfaces.

I will finish here, there are a couple of other chips that may be worth looking at from this camera, but I will look at them and post as separate depots.

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