Rainbow Electronics MAX1611 - Manual (Page 9)

MAX1610/MAX1611
Digitally Controlled CCFL Backlight
Power Supplies
_______________________________________________________________________________________ 9
C9
C4
C3
C8
R5
R6
BATT
SS
CC
SYNC
REF
MINDAC GND
CSAV
CS
OTP
LX
BST
VL
D2
R3
R4
D1
C5
MAX1610
MAX1611*
C2
CCFL
C1
R1
R2
6
5 3 4 2 1
10
Q2 Q1
VIN
12
14
15
10
11
7
13
4
6
5
16
+
9
8
C7
L1
T1
C6 D3
R7
* DIGITAL INTERFACE NOT SHOWN
Table 1. Necessary CCFL Specifications
Once a CCFL has been struck, the voltage required to maintain
light output falls to approximately 550V
RMS . Small tubes may
operate on as little as 250V RMS . The operating voltage of the
CCFL stays relatively constant, even as the tube’s brightness is
varied.
Although CCFLs typically operate at 550V RMS, a higher voltage
is required initially to light up the tube.
CCFL Minimum Strike Voltage
(“Kick-Off Voltage”)
CCFL Typical Operating Voltage
(“Lamp Voltage”)
DESCRIPTION SPECIFICATION
V L
V S
SYMBOL
V RMS
V RMS
UNITS
I L mA RMS
The maximum root-mean-square AC current through a CCFL is
almost always 5mA
RMS. No DC current is allowed through any
CCFL.
CCFL Maximum Operating
Current (“Lamp Current”)
f L kHz
The maximum AC-lamp-current frequency. CCFL Maximum Frequency
(“Lamp Frequency”)
V MIN V
The minimum DC input voltage to the MAX1610/MAX1611 circuit
determines the turns ratio required for the DC-AC conversion
transformer. Decreasing the minimum input voltage increases
the size of the transformer required for a given output power.
DC Power Source Minimum
Input Voltage
Figure 4. Typical Floating-Lamp Application Circuit