Other Parts Discussed in Thread: LOG114
Hello All,
I am using the TL7660 in two applications. The first is the Figure 3. of the data sheet, a simple negative converter. I have 3 components very very simply arranged, I have tested connectivity of all the solder points to assure proper connection. There is the TL7660, and two identical 10uF Solid Tantalum polar capacitors. The capacitors are aligned exactly as in the Figure 3. One capacitor goes between pins 2 and 4, with the positive side toward 2. The other is between the Vout at pin 5 and ground, with the positive side toward ground. I apply either 5V or 3.3V and in both instances the measured voltage at pin 5 is 0.21V (measured between ground and pin5).
The second usage I am working with is as a positive voltage doubler as in Figure 9. of the data sheet. My first question is, since the capacitors aren't labeled, and there are no suggestions for values, is it safe to assume they are not polarized? My values are: C1= 1uF Ceramic and C2 = 10uF Tantalum (polar with the positive facing pin 5 and negative to ground). The two diodes are DB2U308 (Silicon epitaxial planar type).
With this I achieved the positive voltage doubling from 3.7V to roughly 6V (dropout from diodes matched theoretical), my issue materialized when I took the output from this positive doubling and I sent that into a 5V linear regulator (ADP7105). This linear regulator only requires a small polar capacitor on the input, which is the C2 above. This combination does not seem to generate 5V out. Are there innate conceptual issues with placing the TL7660 before a linear voltage regulator? The dropout from the linear regulator is only 1V, so it is expecting 6V pretty constant, would the method by which the TL7660 doubles the voltage change based on the value of C1? As in, does C1 have to be larger to transfer a constant 6V (the ADP7105 has soft start and dropout cutoff features that in theory could be constantly triggered by an unpredictable signal)?
Ideally, my signal conditioning chain is: battery -> voltage doubler -> low noise LDO regulator -> negative converter to provide a stable low noise +5V and -5V rails. These rails are being used for supply current and bias/references for various amplifiers in particular TI's Log114.
Thanks,
Michael Slitts