Charge Pump 'frequency boost' question

[Soulchief]

Hello all,

Charge pumps are new to me..

To get the frequency boost on an "S" or "LT1054" charge pump do you have to manually connect Pin 1 to 8 if they are not connected via circuit board OR are the pins internally connected on these higher end chips?


Thanks for the help,
Mike

[bean]

The LT1054 already internally boosts the frequency out of the audio range. You only need to connect your supply to pin8.

With all the other typical ones you do need to jumper pins 1 and 8. This is for the MAX1044CPA, TC1044SCPA and ICL7660SCPA

[Soulchief]

Thanks for the reply..  2 more quick questions

-- LT1054 - Do you know how the 'Texas Instruments' and the 'Analog Devises' compare? AD is twice the cost of TI..?

-- LT054 internally jumped oscillates at 25kHz (35kHZ max) and the TC1044SCPA and ICL7660SCPA manfully jumped can reach 45kHZ.. Do that sound right to you? (just want to make sure I read them correctly)


Thanks a million,
Mike

[bean]

Thanks for the reply..  2 more quick questions

-- LT1054 - Do you know how the 'Texas Instruments' and the 'Analog Devises' compare? AD is twice the cost of TI..?

-- LT054 internally jumped oscillates at 25kHz (35kHZ max) and the TC1044SCPA and ICL7660SCPA manfully jumped can reach 45kHZ.. Do that sound right to you? (just want to make sure I read them correctly)


Thanks a million,
Mike

1) I think I've only ever used the TI version and it's always worked perfectly.

2) If that's what the datasheet says, sure. In either case it's out of the audio range. There's always a potential concern of heterodyning if you mix it with clocks running at similar frequency ranges but that's really case by case. In most cases it's not a problem.

The most important factor is current draw. The LT1054 is more appropriate when you get over 40-50mA load in your circuit. With low current draws, the other ones listed work fine.

[Soulchief]

Thanks so much Bean!

One last LT1054 thought..

--If using on a PCB that connects pins 1 to 8 via trace, and LT1054 already having Pins 1 and 8 internally connected, do you need to bend away/cut pin leg 1 or is it safe leave have have it jumped twice (internally and pcb)?

Mike

[bean]

Thanks so much Bean!

One last LT1054 thought..

--If using on a PCB that connects pins 1 to 8 via trace, and LT1054 already having Pins 1 and 8 internally connected, do you need to bend away/cut pin leg 1 or is it safe leave have have it jumped twice (internally and pcb)?

Mike

AFAIK, there is no harm in having them connected but someone can correct me if I'm wrong. But, you don't need to cut any pins on the IC. Just use a socket and cut off pin1 of the socket.

[pinkjimiphoton]

if pin 1 and 8 are internally connected,  no need to cut anything off, is there?

i have nothing but problems with these suckers

[Soulchief]

The 'cutting Pin 1 question' came from if the PCB is also already connected with Pins 1 and 8.

From what Bean said and other researching it looks like it's OK to have the LT1054 jumped in two places.. (internally and PCB trace)

[aion]

I don't have the reference right now but awhile back someone in the forum contacted the manufacturer to confirm that an LT1054 would work OK with the pins jumpered. They affirmed that there would be no issues with it.