MAX1739EEP+ Maxim Integrated Products, MAX1739EEP+ Datasheet - Page 14

• Manufacturer Part Number: MAX1739EEP+
• Description: Display Drivers Wide Brightness Rang e CCFL Backlight Con
• Manufacturer: Maxim Integrated Products

Specifications of MAX1739EEP+

• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Wide Brightness Range
CCFL Backlight Controllers
brightness code of ob00000 corresponds to a 9.375%
DPWM duty cycle, and a brightness code of ob11111
corresponds to a 100% DPWM duty cycle. The duty
cycle changes by 3.125% per step, except codes
ob00000 to ob00011 all produce 9.375% (Figure 3).
To disable DPWM and always use 100% duty cycle, set
V
equations above should assume V
of V
and Table 3 shows some typical settings for the bright-
ness adjustment.
In normal operation, V
V
rent control and DPWM control to vary the lamp bright-
ness (Figure 4). In this mode, lamp current control
regulates the average lamp current during a DPWM on-
cycle and not the overall average lamp current.
The MAX1739/MAX1839 analog interface uses an inter-
nal ADC with 1-bit hysteresis to generate the brightness
code used to dim the lamp (see Dimming Range).
CTL/SDA is the ADC’s input, and CRF/SCL is its refer-
ence voltage. The ADC can operate in either positive-
scale ADC mode or negative-scale ADC mode. In
positive-scale ADC mode, the brightness code increas-
Figure 3. DPWM Settings
Table 2. MINDAC Functionality
14
REF
MINDAC = VL
MINDAC = REF
0 ≤ V
MINDAC
MINDAC
______________________________________________________________________________________
, and the MAX1739/MAX1839 use both lamp cur-
MINDAC
Analog Interface and Brightness Code
to VL. Note that with DPWM disabled, the
100
90
80
70
60
50
40
30
20
10
= VL. Table 2 lists MINDAC’s functionality,
< V REF
0
0
4
8
DPWM SETTINGS
BRIGHTNESS CODE
MINDAC
12
DPWM disabled (always on 100% duty cycle). Operates in lamp current control only.
(Use V
DPWM control enabled, duty cycle ranges from 9% to 100%. Lamp current control is disabled
(always maximum current).
The device uses both lamp current control and DPWM.
16
20
is set between 0 and
MINDAC
MINDAC
24
28
= 0 in the equations.)
32
= 0 instead
es from 0 to 31 as V
negative-scale mode, the brightness scale decreases
from 31 to 0 as V
The analog interface’s internal ADC uses 1-bit hystere-
sis to keep the lamp from flickering between two codes.
V
required to transition the brightness code as V
increases and can be calculated as follows:
where n is the current selected brightness code. V
negative threshold is the voltage required to transition
the brightness code as V
calculated as follows:
Figure 5 shows a graphic representation of the thresh-
olds. CRF/SDA’s and CTL/SCL’s input voltage range is
2.7V to 5.5V.
Figure 4. Combined Power Level
CTL
’s positive threshold (V
(positive-scale ADC mode, MODE = GND)
(negative-scale ADC mode, MODE = REF)
(positive-scale ADC mode, MODE = GND)
(negative-scale ADC mode, MODE = REF)
100
90
80
70
60
50
40
30
20
10
0
V
V
V
CTL(TH)
CTL(TH)
CTL(TH)
0
CTL
V
CTL(TH)
4
LAMP CONTROL CURRENT)
COMBINED POWER LEVEL
increases from 0 to V
CTL
8
(BOTH DPWM AND
= (33 - n) / 33 V
= (31 - n) / 33 V
= (n + 2) / 33 V
BRIGHTNESS CODE
12
= n / 33 V
increases from 0 to V
CTL
16
CTL(TH)
decreases and can be
20
CRF
24
CRF
CRF
CRF
) is the voltage
28
CRF
32
(Figure 5) .
CRF
CTL
CTL
. In
’s