Datasheet
Table Of Contents
- Figure 1. Application circuit
- 1 Pin settings
- 2 Maximum ratings
- 3 Electrical characteristics
- 4 Functional description
- 5 Application information
- 5.1 Input capacitor selection
- 5.2 Inductor selection
- 5.3 Output capacitor selection
- 5.4 Compensation network
- 5.5 Thermal considerations
- 5.6 Layout considerations
- 5.7 Application circuit
- Figure 18. Demonstration board application circuit
- Table 9. Component list
- Figure 19. PCB layout (component side)
- Figure 20. PCB layout (bottom side)
- Figure 21. PCB layout (front side)
- Figure 22. Junction temperature vs output current
- Figure 23. Junction temperature vs output current
- Figure 24. Junction temperature vs output current
- Figure 25. Efficiency vs output current
- Figure 26. Efficiency vs output current
- Figure 27. Efficiency vs output current
- Figure 28. Load regulation
- Figure 29. Line regulation
- Figure 30. Short circuit behavior
- Figure 31. Load transient: from 0.1 A to 0.7 A
- Figure 32. Soft-start
- 6 Application ideas
- 7 Package mechanical data
- 8 Order codes
- 9 Revision history
Functional description L5980
12/42 Doc ID 13003 Rev 6
4.3 Error amplifier and compensation
The error amplifier (E/A) provides the error signal to be compared with the sawtooth to
perform the pulse width modulation. Its non-inverting input is internally connected to a 0.6 V
voltage reference, while its inverting input (FB) and output (COMP) are externally available
for feedback and frequency compensation. In this device the error amplifier is a voltage
mode operational amplifier so with high DC gain and low output impedance.
The uncompensated error amplifier characteristics are the following:
In continuos conduction mode (CCM), the transfer function of the power section has two
poles due to the LC filter and one zero due to the ESR of the output capacitor. Different
kinds of compensation networks can be used depending on the ESR value of the output
capacitor. In case the zero introduced by the output capacitor helps to compensate the
double pole of the LC filter a type II compensation network can be used. Otherwise, a type
III compensation network has to be used (see Chapter 5.4 for details about the
compensation network selection).
Anyway the methodology to compensate the loop is to introduce zeros to obtain a safe
phase margin.
Table 5. Uncompensated error amplifier characteristics
Error amplifier Value
Low frequency gain 100 dB
GBWP 4.5 MHz
Slew rate 7 V/μs
Output voltage swing 0 to 3.3 V
Maximum source/sink current 25 mA/40 mA