LED6000PHTR datasheet(37/49 Pages) STMICROELECTRONICS

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LED6000

Application notes - alternative topologies

This schematic also includes additional circuitry:



A level shifter network for the proper dimming operation, since the LED6000 local

ground (ICGND) is referred to the negative output voltage given by the voltage drop

across the LEDs and the sensing resistor. This function is implemented by Q1, R15,

R16 and R17. However, due to limited control loop bandwidth, the dimming operation in

buck-boost topology is quite limited in terms of the minimum achievable DIM pulse.



An external overvoltage protection which avoids the IC damage in case of the LED

open row fault. This function is implemented by a Zener diode, D2, R7 and the sensing

resistor, RSNS = R13.

In case the LED string is disconnected the maximum output voltage is given by:

Equation 31

Equation 31, in addition to Equation 27, must be verified in order avoid the LED6000 to be

exposed to electrical stress outside the allowed range (seeTable 2 on page 7 for details).

The series resistor, R7, must be selected in order to limit the maximum current flowing

through the D2, as shown in Equation 32.

Equation 32

The compensation network design strategy for buck-boost topology is described in

Section 6.4 on page 44.

Figure 24. Inverting buck-boost PCB layout (component side)

MAX

OUT





SNS





LED6000PHTR 数据表(PDF) 37 Page - STMicroelectronics