Figure 31. Floating-boost reference schematic

R9

33k

C7

100nF

R1

0

R16

100k

TP2

SYNCH

R17

22k

L2

4.7uH

R4

0

D2

BZX384-C40

TP10 GND

C11

1nF

Q1

3

2

L1

47uH

R6 4.7k

TP6

GND

C6

1uF

U1

A L E D 6 0 0 0

DIM

12

VIN_2

3

SS

6

SYNCH

7

FSW

10

ILIM

11

COMP

8

EN

5

FB

9

GND

16

VCC

4

LX_1

13

LX_2

14

VIN_1

2

VBIAS

1

BOOT

15

TP

17

C8

N.M.

+

C12

R5 N.M.

C5

4.7uF

TP7

ICGND

C9

33nF

TP5

EN

D1

STPS3L60

TP1

DIM

R12

100k

T1

1

3

R3 0

R13

1

R15

1k

TP4

VLED+

TP3

VIN

TP9

VLED-

C10 68nF

C3

N.M.

R7

22k

R8

47k

R2

0

VINF

VINF

Figure 31. Floating-boost reference schematic shows the schematic circuit for an LED current source based on

floating-boost topology. The expected input voltage is 13 V, with 5 V to 30 V range, and it can drive a string

composed of 10 white LEDs with 0.25 A DC.

This schematic also includes two additional circuits:

•

A level shifter network for proper dimming operation, since the ALED6000 local ground is different from the

board GND. This function is implemented by Q1, R15, R16 and R17. However, due to limited control loop

bandwidth, the dimming operation in floating-boost topology is quite limited in terms of minimum achievable

DIM pulse

•

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

VOUT,MAX=VFB+VD2

(38)

must be verified in order to avoid the ALED6000 to be exposed to electrical stress outside the allowed range (see

Table 5. Electrical characteristics for details).

The series resistor, R7, must be selected in order to limit the maximum current flowing through D2, as shown in

The compensation network design strategy for floating-boost topology is described in Section 8.4 Compensation

strategy for alternative topologies.

ALED6000

Floating boost

DS13018 - Rev 4

page 34/45