Datasheet
Table Of Contents
- Figure 1. Typical application circuit
- 1 Pin settings
- 2 Maximum ratings
- 3 Electrical characteristics
- 4 Functional description
- 5 Application notes - buck conversion
- 5.1 Closing the loop
- 5.2 GCO(s) control to output transfer function
- 5.3 Error amplifier compensation network
- 5.4 LED small signal model
- 5.5 Total loop gain
- 5.6 Compensation network design
- 5.7 Example of system design
- 5.8 Dimming operation
- 5.9 Component selection
- 5.10 Layout considerations
- 5.11 Thermal considerations
- 5.12 Short-circuit protection
- 5.13 Application circuit
- 6 Application notes - alternative topologies
- 7 Package mechanical data
- 8 Ordering information
- 9 Revision history
LED5000 Application notes - buck conversion
Doc ID 023951 Rev 1 17/51
Figure 9. Load equivalent circuit
As a consequence the LED equivalent circuit gives the α
LED
(s) term correlating the output
voltage with the high impedance FB input:
Equation 13
5.5 Total loop gain
In summary, the open loop gain can be expressed as:
Equation 14
5.6 Compensation network design
The maximum bandwidth of the system can be designed up to f
SW
/6 to guarantee a valid
small signal model.
Equation 15
where
ω
P
(
Equation 3
) is the pole introduced by the power components. The following
calculations are valid in the hypothesis that BW >
ω
P
which is the typical condition.
VINVIN
Rd1Rd1
COUTCOUT
LL
Rd2Rd2
RsRs
Dled1Dled1
RsRs
D1D1
DD
COUTCOUT
VINVIN
LL
Dled2Dled2
AM13493v1
α
LED
n
LED
()
R
SENSE
n
LED
r
LED
R
SENSE
+⋅
------------------------------------------------------------=
Gs() G
CO
s() A
0
s() α
LED
n
LED
()⋅⋅=
ω
P
2 π⋅
-------------
BW< BW
MAX
≤
f
SW
6
---------=