Datasheet

LMP8646EB User’s Guide
November 2011 Page 10 of 20 SNOU010
For example, if Rg = 73 kOhm and the chosen bandwidth is 2 kHz, then the initial Cg value can be
calculated as:
  
  
nFCg
HzkkOhm
Cg
BandwidthRg
Cg
109.0
2732
1
2
1





Once Cg is chosen, capture the output regulator current plot and adjust Cg to get the desired value.
5. Step 4: Choose the output resistor, ROUT, for LMP8646
For the resistive load application, we found that ROUT plays a very small role in the performance.
ROUT was important in the supercap application because it affects the initial current error. Because
current is directly proportional to voltage for a resistive load, the output current is not large at startup.
In fact, the larger the ROUT, the longer it takes for the output voltage to reach its final value. In our
example, we chose a value of 2 kOhm for ROUT.
6. Step 5: Adjusting Components – capture the output current and output voltage plots and adjust the
components as necessary. The most common component to adjust is Cg for the bandwidth.
A plot for the load current (yellow), output voltage of the LM3102 (pink) can be seen in Figure 6.
Figure 6 – Plots for the Resistive Load Application