cat4106 ON Semiconductor, cat4106 Datasheet - Page 10

• Manufacturer Part Number: cat4106
• Description: 6w Quad Channel Dc/dc Led Driver With Diagnostics
• Manufacturer: ON Semiconductor

CAT4106
BLOCK DIAGRAM
DEVICE OPERATION
In a typical application, the CAT4106 drives an LED
array consisting of up to four separate strings. A
single external resistor value is used to select the
drive level in all output channels. Each channel
provides a very well regulated and tightly matched
bias current on all LED strings.
An integrated DC/DC boost converter is used to
generate the high voltage output required to power the
LED strings. Up to a maximum of 6 W of LED power
can be delivered when powered from a 12 V supply.
To offer improved performance, the device also allows
the user to set the operating voltage level on the
output drive channels. A pair of external resistors is
used to control the nominal channel voltage, during
normal operation. The resulting output voltage (LED
anodes) will be equal to the sum of the adjusted
channel voltage plus the maximum forward voltage
present on any string.
The CAT4106 provides four tightly matched current
sinks to accurately regulate LED current in each
channel. Up to 175 mA per channel can be
programmed by selecting a suitable value for the
Doc. No. MD-5037, Rev. A
EN/DIM
V
L
VIN
Supply
PWM_DIM
200 k
300mV
Ω
Figure 4. CAT4106 Simplified Functional Block Diagram
L
RSET
Drive Control
1MHz PWM
IRSETx100
Shutdown
Controller
Controller
Delay
OVP
R1
System
EN/SD
SW
I1
1A
1
Ω
GND
VFMAX
D
R5
I2
10
Ctrl/Fault
Detector
external R1 resistor (connected between RSET and
GND pins).
LED CURRENT SETTING
The CAT4106 provides four tightly matched current
sinks to accurately regulate LED current in each
channel. The LED current is set by the external
resistor R1 connected between the feedback pin (FB)
and
relationship between the resistor value and the LED
current per channel.
I3
R4
PGND
LED current per channel (mA)
ground.
I4
VFMIN
R6
Table 1. Resistor R1 and LED current
R7
0 - 175 mA
R
1
≈
103
The
×
FAULT
CTRL
FB
100
150
LED1
LED2
LED3
LED4
10
20
30
50
LED
following
C3
current
Characteristics subject to change without notice
µC Diagnostics
M_Parallel
N_Series
1
Cluster
2 .
R2
R3
per
LED
© 2009 SCILLC. All rights reserved.
V
formula
channel
R1 (Ω)
12.4 k
6.19 k
4.12 k
2.49 k
1.24 k
LEDn
LED1
gives
820
the