Negative voltage charge pump not working

[FreshmanNewbie]

I'm using the TC7662B but having a hard time using the Simple Negative Voltage Converter. I have implemented the diagram referenced in the datasheet on page 4 and has a +12V input. I'm trying to get a -12V output but reading -5V. I do not have pin 6 connected to the ground.

Do the capacitors need to be changed from 10uF in accordance with the input? Or Is there another issue that could be causing this issue?

 

[KlausST]

Hi,

most likely the circuit in the datasheet is correct.
If your circuit does not work as expected, then:
* either your expectation is wrong
* your circuit includes a mistake
* you used different test conditions

So if your car does not work .... do you go to the garage with only the users manual in hand, leaving the car at home?

Same is here. If your circuit does not work ... then we need to see your circuit. Your schematic (not the one from the datasheet), a photo of your circuit, a wiring diagram of your circuit, the test conditions of your circuit, and information where you connected a your DVM, your load, what "is" your load...

Klaus

 

[stenzer]

Hi,

it is advertisedto create a negative version of the applied supply voltage. Further, there is no equation indicating a relationship between output voltage and used capacitance (except output impedance).

How does your circuitry looks like, breadboard?
What is the connected load?
How have you measured the output voltage, DMM or oscillcope?

BR

 

[BradtheRad]

* Performance depends on the source waveform, whether it's: a) bipolar AC, or b) pulsed DC.

* When inverting polarity some wattage is used up just to change polarity. You may find it's necessary to make a voltage tripler or quadrupler. This is done by attaching additional charge pump stages.

* Multiple stages can be arranged: a) Villard style, or b) half-wave parallel style. They're not identical. Each has diodes connected in series pointing in the same direction. However capacitors need attention as to their connection and orientation.

* Check capacitor voltages when running. Each cap should acquire several volts. If any cap measures only a few mV then the network is attached incorrectly to the power source.

 

[danadakk]

What is your load ? Resistance ?

Do you see ripple on output 5V that indicates its switching ?

Your input is 12V right, not 5V ? These notes, when yiou load outout the input'is still
12V ?

Keep in mind the following is true (output is NOT a regulated V source) :

Regards, Dana.