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PDF DS3988 Data sheet ( Hoja de datos )
| Número de pieza | DS3988 | |
| Descripción | 8-Channel Cold-Cathode Fluorescent Lamp Controller | |
| Fabricantes | Maxim Integrated Products | |
| Logotipo |  |
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Rev 0; 4/05
www.DataSheet4U.com
8-Channel Cold-Cathode
Fluorescent Lamp Controller
General Description
The DS3988 is an 8-channel controller for cold-cathode
fluorescent lamps (CCFLs) used to backlight liquid
crystal displays (LCDs) in TV and PC monitor applica-
tions. The DS3988 supports configurations of 1 to 8
lamps, and multiple DS3988 controllers can be cascad-
ed to support applications requiring more than 8 lamps.
LCD Televisions
LCD PC Monitors
Applications
Ordering Information
PART
TEMP RANGE
DS3988T
-40°C to +85°C
DS3988T+
-40°C to +85°C
+Denotes lead-free package.
PIN-PACKAGE
48 TQFP
48 TQFP
Pin Configuration
TOP VIEW
GA1
GB1
LCM1
OVD1
GA2
GB2
LCM2
OVD2
GA3
GB3
LCM3
OVD3
1
2
3
4
5
6
7
8
9
10
11
12
DS3988
36 OVD8
35 LCM8
34 GB8
33 GA8
32 OVD7
31 LCM7
30 GB7
29 GA7
28 OVD6
27 LCM6
26 GB6
25 GA6
48-LEAD TQFP
7 x 7 x 1.0mm
Features
♦ High-Density CCFL Controller for LCD TV and PC
Monitor Backlights
♦ Can Be Easily Cascaded to Support More Than
8 Lamps
♦ Minimal External Components
♦ Analog Brightness Control
♦ Per-Channel Lamp Control Ensures Equal
Brightness Among Lamps and Maximizes Lamp
Life
♦ Gate Driver Phasing Minimizes DC Supply Current
Surges
♦ Per-Channel Lamp Fault Monitoring for Lamp
Open, Lamp Overcurrent, Failure to Strike, and
Overvoltage Conditions
♦ Accurate (±5%) Independent On-Board Oscillators
for Lamp Frequency (40kHz to 80kHz) and DPWM
Burst Dimming Frequency (22.5Hz to 440Hz)
♦ Can Be Synchronized to External Sources for the
Lamp and DPWM Frequencies
♦ <10% to 100% Dimming Range
♦ Programmable Soft-Start Minimizes Audible
Transformer Noise
♦ I2C-Compatible Serial Port and On-Board
Nonvolatile (NV) Memory Allow Device
Customization
♦ 8-Byte NV User Memory for Storage of Serial
Numbers and Date Codes
♦ 4.5V to 5.5V Single-Supply Operation
♦ -40°C to +85°C Temperature Range
♦ 48-Lead TQFP (7mm x 7mm) Package
I2C is a trademark of Philips Corp. Purchase of I2C compo-
nents from Maxim Integrated Products, Inc., or one of its subli-
censed Associated Companies, conveys a license under the
Philips I2C Patent Rights to use these components in an I2C
system, provided that the system conforms to the I2C Standard
Specification as defined by Philips.
Typical Operating Circuit appears at end of data sheet.
______________________________________________ Maxim Integrated Products 1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
1 page  
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8-Channel Cold-Cathode
Fluorescent Lamp Controller
(VCC = +5.0V, TA = +25°C, unless otherwise noted.)
Typical Operating Characteristics
ACTIVE SUPPLY CURRENT
vs. SUPPLY VOLTAGE
19 fLF:OSC = 71kHz
GATE QC = 3.5nC
17
DPWM = 100%
15
DPWM = 50%
13
11 DPWM = 10%
9
7 SVM = 0V
5
4.5 4.7 4.9 5.1 5.3 5.5
SUPPLY VOLTAGE (V)
ACTIVE SUPPLY CURRENT
vs. TEMPERATURE
20
19 VCC = 4.5V
VCC = 5.5V
VCC = 5.0V
18
17
16
15
14
13
12
11 fLF:OSC = 71kHz
GATE QC = 3.5nC
10
-40 -15 10
DPWM = 100%
35 60 85
TEMPERATURE (°C)
INTERNAL FREQUENCY CHANGE
vs. TEMPERATURE
4
3
2
LAMP FREQUENCY
1
0
-1 DPWM FREQUENCY
-2
-3
-4
-40
-15 10 35 60
TEMPERATURE (°C)
85
TYPICAL OPERATION AT 12V
10µs
5.0V GA
10µs
5.0V GB
10µs
2.0V LCM
10µs
2.0V OVD
TYPICAL OPERATION AT 15V
10µs
5.0V GA
10µs
5.0V GB
10µs
2.0V LCM
10µs
2.0V OVD
TYPICAL OPERATION AT 18V
10µs
5.0V GA
10µs
5.0V GB
10µs
2.0V LCM
10µs
2.0V OVD
TYPICAL STARTUP WITH SVM
2ms
2.0V SVM
2ms
5.0V GB
2ms
2.0V LCM
2ms
2.0V OVD
BURST DIMMING AT 150Hz AND 10%
1ms
5.0V GA
1ms
5.0V GB
1ms
2.0V LCM
1ms
2.0V OVD
_____________________________________________________________________ 5
5 Page 
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8-Channel Cold-Cathode
Fluorescent Lamp Controller
ANALOG DIMMING
CONTROL VOLTAGE
0.5V
DPWM
SIGNAL
22.5Hz TO 440Hz
RESISTOR TO SET THE
DIMMING FREQUENCY
RESISTOR-SET DIMMING CLOCK
2.0V
BRIGHT
PSYNC (OUTPUT)
POSC
ANALOG DIMMING
CONTROL VOLTAGE
0.5V
DPWM
SIGNAL
EXTERNAL
DIMMING CLOCK
22.5Hz TO 440Hz
22.5Hz to 440Hz
EXTERNAL DIMMING CLOCK
2.0V
BRIGHT
PSYNC (OUTPUT)
POSC
Figure 3. DPWM Source Configuration Options
DPWM
SIGNAL
22.5Hz TO 440Hz
BRIGHT
PSYNC (OUTPUT)
POSC
Figure 4. The DPWM Receiver Configuration
To generate the DPWM signal internally, the DS3988
requires a clock (referred to as the dimming clock) to
set the DPWM frequency. The user can supply the dim-
ming clock by setting POSCS = 1 in CR1 and applying
an external 22.5Hz to 440Hz signal at the POSC pin, or
DS3988’s clock can be generated by the DS3988’s
oscillator (set POSCS = 0 in CR1), in which case the
frequency is set by an external resistor at the POSC
pin. These two dimming clock options are shown in
Figure 3. Regardless of whether the dimming clock is
generated internally or sourced externally, the POSC1
and POSC2 bits in CR2 must be set to match the
desired dimming clock frequency.
When the DPWM signal is generated internally, its duty
cycle (and, thus, the lamp brightness) is controlled by a
user-applied analog voltage at the BRIGHT input. A
BRIGHT voltage less than 0.5V will cause the DS3988 to
operate with the minimum burst duty cycle, providing
the lowest brightness setting, while any voltage greater
than 2.0V will cause a 100% burst duty cycle (i.e., lamps
always being driven), which provides the maximum
brightness. For voltages between 0.5V and 2V the duty
cycle will vary linearly between the minimum and 100%.
The internally generated DPWM signal is available at
the PSYNC I/O pin (set RGSO = 0 in CR1) for sourcing
to other DS3988s, if any, in the circuit. This allows all
DS3988s in the system to be synchronized to the same
DPWM signal. The DS3988 that is generating the
DPWM signal for other DS3988s in the system is
referred to as the DPWM source.
When the DPWM signal is provided by an external
source, either from the PSYNC pin of another DS3988 or
from some other user-generated source, it is input into the
PSYNC I/O pin of the DS3988. In this mode, the BRIGHT
and POSC inputs are disabled and should be grounded
(see Figure 4). When multiple DS3988s are used in a
design, DS3988s configured to use externally generated
DPWM signals are referred to as DPWM receivers.
Lamp Frequency Configuration
The DS3988 can generate its own lamp frequency clock
internally (set LFSS = 0 in CR1), which can then be
sourced to other DS3988s if required, or the lamp clock
can be supplied from an external source (set LFSS = 1 in
CR1). When the lamp clock is internally generated, the
frequency (40kHz to 80kHz) is set by an external resistor
at the LOSC. In this case, the DS3988 can act as a lamp
frequency source because the lamp clock is output at
the LSYNC I/O pin for synchronizing any other DS3988s
configured as lamp frequency receivers.
The DS3988 acts as a lamp frequency receiver when
the lamp clock is supplied externally. In this case, a
40kHz to 80kHz clock must be supplied at the LSYNC
I/O. The external clock can originate from the LSYNC
I/O of a DS3988 configured as a lamp frequency
source or from some other source.
____________________________________________________________________ 11
11 Page | ||
| Páginas | Total 23 Páginas | |
| PDF Descargar | [ Datasheet DS3988.PDF ] | |
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