Toshiba TB6504F Stepper Motor Driver

This is another chip from the Panasonic camcorder. This time it is a PWM chopper type sinusoidal micro step Bipolar stepping motor driver manufactured by Toshiba. It was used to drive one of the motors on the VCR recording/playback assembly. Although this is a 1994 manufactured part, I was able to find a datasheet.

Here is the die photo  (Die size 4.28 x 3.19 mm)

There are absolutely no die markings at all on the chip which is unusual.

This is the block diagram from the datasheet

The bridge driver outputs are clearly on the right, this is my take on the layout of the chip

 

 

 

The datasheet states the chip is made on a high voltage Bi-CMOS process, it has two levels of metal and minimum geometry of 5-6μm.  Looking at the die most of the die is covered in Bipolar transistors and diffusion resistors. Two colorful diffusion areas are visible, the pink regions and the light blue areas.  I can see no polysilicon layer at all, or any transistors that look like MOSFETs.  It is possible there are MOSFETS in the bridge driver (as this are is covered in two dense metal layers).  I think the MOS transistors (If used) are high voltage devices with a metal gate.

This is the one of the bridge drivers (Imaged with my 20x objective)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

As you scan across the device I notice two things:

  •  the metallization changes with two layers heavily used in the bridge drivers, moderately used in comparator and current control, and only single metal being used in the decoder region. Odd, perhaps they reused an older decoder circuit that was made in a single metal process
  • The type of transistor layout used is different in the different regions

Here is an image from the comparator area with two different Bipolar transistor layouts visible, and the two levels of metal

Here is another image taken from the current control region with different transistor styles and two level metal still visible

And here is an image from the decoder region where the transistor layouts are very different (And difficult to identify) and only one level of metal is visible

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