CD4046B: Frequency multiplication circuit with at least 100 times magnification

Shawn_Wang

Part Number: CD4046B
Other Parts Discussed in Thread: UCC21225A, , CD4518B, TCA6424A, SN74LV4046A

Hi team

My customer wants to know whether TI has the solution to multiply a 100Hz input square wave signal to 100kHz (or at least 10kHz) output?

The purpose is to reduce the size of the transformer.

The system diagram shown below:

MCU ---> 100Hz square wave ------> Transformer -----> Rectifier ------> DC voltage for the supply of isolated gate driver(UCC21225A or ADUM7223).

I found a solution consist of CD4046B and CD4518B and multiplication time is 100.

I am not sure whether it could be suitable to this application? Look forward to your comments.

over 3 years ago

0 Sebastian Muriel over 3 years ago

TI__Genius 16140 points

Hi Shawn,

I'm looking into your question and will give you a response as soon as possible.

Thanks,

Sebastian

0 Sebastian Muriel over 3 years ago in reply to Sebastian Muriel

TI__Genius 16140 points

Hi Shawn,

The datasheet measurements for the CD4046B only test for C1 up to 1µF at VDD 5V, 10V, and 15V. If you replaced C1 with a 10x10^-4 µF capacitor and set VDD to 10V with the same resistor values you have, you should get a 10KHz output from the CD4046B (When VCOin = VDD/2). If you need to use component values not tested in the datasheet you must test your design because we cannot guarantee that the device will work properly.

Regards,

Sebastian

0 Shawn_Wang over 3 years ago in reply to Sebastian Muriel

TI__Expert 3811 points

Hi Sebastian

Thanks for your information.

CD4046B and CD4518B are two very old devices and do we have new alternatives?

In addition, considering that out 10kHz output square wave would be connected to transformer, could you help check whether the following solution is good? Is it suitable to supply UCC21225A VCC1?

MCU I2C interface--->TCA6424A(IO expander with I2C interface) ----> 100Hz square wave output ------> CD4046B + CD4518B ------> 10kHz square wave output ------> Transformer -----> Rectifier ------> DC voltage for the supply of isolated gate driver(UCC21225A).

0 Sebastian Muriel over 3 years ago in reply to Shawn_Wang

TI__Genius 16140 points

Hi Shawn,

If you need over 5.5V support there are no other P2P devices in our portfolio that support this application. The CD4046B will have a drive strength of 2.6mA with VDD at 10V so this set up will only work if that is enough drive to power your transformer. If the CD4046B meets the input parameters for the transformer and the UCC212225A input is within the voltage range of 3V to 18V it should work properly.

Regards,

Sebastian

0 Shawn_Wang over 3 years ago in reply to Sebastian Muriel

TI__Expert 3811 points

Hi Sebastian

No p2p requirement and could you help give a new solution for the frequency multiplication requirement?

0 Sebastian Muriel over 3 years ago in reply to Shawn_Wang

TI__Genius 16140 points

Hi Shawn,

Just to clarify, you don't need 3V to 18V support?

0 Shawn_Wang over 3 years ago in reply to Sebastian Muriel

TI__Expert 3811 points

Hi Sebastian

UCC21225A VCCI supply voltage is 3-V to 18-V. But considering the transformer turns ratio, the output voltage at secondary side could be higher than primary side.

Let me know if you have any questions.

0 Sebastian Muriel over 3 years ago in reply to Shawn_Wang

TI__Genius 16140 points

Hi Shawn,

The SN74LV4046A is a direct replacement for the CD4046B. The SN74LV4046A operates the same as the SN74HC4046A which has better documentation. I would recommend R1 and R2 to be 100kΩ and C1 to be 0.01µF for a 10kHz output with a Vcc = 5V. I pulled these values from Figure 24 in this application report CMOS Phase-Locked-Loop Applications Using the CD54/74HC/HCT4046A and CD54/74HC/HCT7046A. I recommend tuning these RC values to get the correct output before finalizing your design because we currently do not have a good simulation option.

Regards,

Sebastian

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CD4046B: Frequency multiplication circuit with at least 100 times magnification