MAX8790A Ver la hoja de datos (PDF) - Maxim Integrated
Número de pieza
componentes Descripción
Fabricante
MAX8790A
Maxim Integrated
MAX8790A Datasheet PDF : 22 Pages
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MAX8790A
Six-String White LED Driver with Active
Current Balancing for LCD Panel Applications
The PLL is disabled in DPWM mode; consequently, the
BRT frequency is not limited by fPLL. The maximum BRT
frequency is determined by the minimum BRT ontime of
50μs and the minimum acceptable dimming factor. If a 1%
dimming factor is needed, the maximum BRT frequency is
200Hz. If a 10% dimming factor is acceptable, the maxi-
mum BRT frequency is 2kHz.
In analog dimming mode, load-current transients can
occur when the BRT frequency abruptly changes on the
fly. Large regulation transients induce a flash on the LED
load that is observable with the naked eye and should
therefore be avoided. Such annoying flashes can be
eliminated by dynamically changing the ENA pin setting.
When a capacitor is connected to the CPLL pin and the
ENA pin is grounded, the PLL continues to run but does
not affect the dimming. When fast PLL lockup transitions
are required, the ENA pin can be momentarily pulled to
ground; after the PLL is locked up, ENA can be pulled
high to reenable PLL in dimming control.
Thermal Shutdown
The MAX8790A includes a thermal-protection circuit.
When the local IC temperature exceeds +170°C (typ),
the controller and current sources shut down and do not
restart until the die temperature drops by 15°C.
Design Procedure
All MAX8790A designs should be prototyped and tested
prior to production. Table 3 provides a list of power com-
ponents for the typical applications circuit. Table 4 lists
component suppliers. External component value choice is
primarily dictated by the output voltage and the maximum
load current, as well as maximum and minimum input
voltages. Begin by selecting an inductor value. Once L is
known, choose the diode and capacitors.
Table 3. Component List
CIRCUIT
FIGURE 1
FIGURE 1
FIGURE 1
FIGURE 3
Switching
Frequency
1MHz
750kHz
500kHz
750kHz
White LED
3.2V (typ), 3.5V (max) at
20mA
Nichia NSSW008C
Number of 6 series x 6 parallel,
White LEDs 20mA (max)
Input Voltage 4.5V to 5.5V, VCC = IN
Inductor L1
2.2µH, 2.5A power inductor
Sumida CDRH5D16-2R2
3.2V (typ), 3.5V (max) at
20mA
Nichia NSSW008C
3.2V (typ), 3.5V (max) at
20mA
Nichia NSSW008C
8 series x 6 parallel,
20mA (max)
10 series x 6 parallel,
25mA (max)
7V to 21V
7V to 21V
4.7µH, 2.05A power inductor 4.7µH, 3.6A power inductor
Sumida CDRH5D16-4R7 Sumida CDRH8D28-4R7
3.2V (typ), 3.5V (max) at
20mA
Nichia NSSW008C
6 series x 6 parallel,
20mA (max)
2.8V to 5.5V, VCC = 5V
0.9µH, 4.7A power inductor
Sumida CDRH5D16-0R9
Input
Capacitors
10µF ±10%, 10V X5R
10µF ±10%, 25V X5R
10µF ±10%, 25V X5R
10µF ±10%, 10V X5R
ceramic capacitor (1206) ceramic capacitor (1206) ceramic capacitor (1206) ceramic capacitor (1206)
Murata GRM31MR61A106K Murata GRM31CR61E106KA Murata GRM31CR61E106KA Murata GRM31MR61A106K
COUT Output
Capacitor
2.2µF ±10%, 50V X7R
ceramic capacitor (1x)
Murata GRM31CR71H225K
2.2µF ±10%, 50V X7R
ceramic capacitor (1206)
(1x)
Murata GRM31CR71H225K
4.7µF ±10%, 50V X7R
ceramic capacitor (1210)
(1x)
Murata GRM32ER71H475K
2.2µF ±10%, 50V X7R
ceramic capacitor (1x)
Murata GRM31CR71H225K
MOSFET N1
60V, 2.8A n-channel
30V, 3A n-channel MOSFET
(6-pin SC70)
Vishay Si1402DH
MOSFET (6-pin TSOP)
Fairchild Semiconductor
FDC5612
Sanyo Semiconductor
CPH6424
60V, 6A n-channel MOSFET 30V, 4.9A n-channel
(PowerPAK 1212-8)
MOSFET (6-pin TSOP)
Vishay Si7308DN
Vishay Si3456BDV
Diode
2A, 30V Schottky diode
Rectifier D1 Nihon EC21QS03L
2A, 40V Schottky diode
Toshiba CMS11
Nihon EC21QS04
3A, 60V Schottky diode
Nihon EC31QS06
3A, 30V Schottky diode
Nihon EC31QS03L
Sense
Resistor
50mΩ ±1%, 1/2W
IRC LRC-LRF-1206LF-01-
R050-F
56mΩ ±1%, 1/2W
IRC LRC-LRF-1206LF-01-
R056-F
40mΩ ±1%, 1/2W
IRC LRC-LRF-1206LF-01-
R040-F
30mΩ ±1%, 1/2W
IRC LRC-LRF-1206LF-01-
R030-F
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