MAX8790AETP+T Maxim Integrated Products, MAX8790AETP+T Datasheet - Page 16

• Manufacturer Part Number: MAX8790AETP+T
• Description: IC LED DRVR WHITE BCKLGT 20-TQFN
• Manufacturer: Maxim Integrated Products
• Type: Backlight, White LEDr

Specifications of MAX8790AETP+T

• Topology: PWM, Step-Up (Boost)
• Number Of Outputs: 6
• Internal Driver: No
• Type - Primary: Backlight
• Type - Secondary: White LED
• Frequency: 1MHz
• Voltage - Supply: 4.5 V ~ 5.5 V, 5.5 V ~ 26 V
• Voltage - Output: 5V
• Mounting Type: Surface Mount
• Package / Case: 20-TQFN Exposed Pad
• Operating Temperature: -40°C ~ 85°C
• Current - Output / Channel: 27mA
• Internal Switch(s): Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Efficiency: -
• Lead Free Status / Rohs Status: Details

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 f
BRT frequency is determined by the minimum BRT on-
time 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 maximum 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
Table 3. Component List
16
Switching
Frequency
White LED
Number of
White LEDs
Input Voltage 4.5V to 5.5V, V
Inductor L1
Input
Capacitors
C
Capacitor
MOSFET N1
Diode
Rectifier D1
Sense
Resistor
OUT
CIRCUIT
______________________________________________________________________________________
Output
1MHz
3.2V (typ), 3.5V (max) at
20mA
Nichia NSSW008C
6 series x 6 parallel,
20mA (max)
2.2µH , 2.5A p ow er i nd uctor
Sumida CDRH5D16-2R2
10µF ±10%, 10V X5R
ceramic capacitor (1206)
Murata GRM31MR61A106K
2.2µF ±10%, 50V X7R
ceramic capacitor (1x)
Murata GRM31CR71H225K
30V, 3A n-channel MOSFET
(6-pin SC70)
Vishay Si1402DH
2A, 30V Schottky diode
Nihon EC21QS03L
50mΩ ±1%, 1/2W
IRC LRC-LRF-1206LF-01-
R050-F
FIGURE 1
CC
= IN
PLL
. The maximum
750kHz
3.2V (typ), 3.5V (max) at
20mA
Nichia NSSW008C
8 series x 6 parallel,
20mA (max)
7V to 21V
4.7µH , 2.05A p ow er i nd uctor
Sumida CDRH5D16-4R7
10µF ±10%, 25V X5R
ceramic capacitor (1206)
M ur ata GRM 31C R61E 106KA
2.2µF ±10%, 50V X7R
ceramic capacitor (1206)
(1x)
Murata GRM31CR71H225K
60V, 2.8A n-channel
MOSFET (6-pin TSOP)
Fairchild Semiconductor
FDC5612
Sanyo Semiconductor
CPH6424
2A, 40V Schottky diode
Toshiba CMS11
Nihon EC21QS04
56mΩ ±1%, 1/2W
IRC LRC-LRF-1206LF-01-
R056-F
FIGURE 1
ground; after the PLL is locked up, ENA can be pulled
high to reenable PLL in dimming control.
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.
All MAX8790A designs should be prototyped and tested
prior to production. Table 3 provides a list of power
components 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.
500kHz
3.2V (typ), 3.5V (max) at
20mA
Nichia NSSW008C
10 series x 6 parallel,
25mA (max)
7V to 21V
4.7µH , 3.6A p ow er i nd uctor
Sumida CDRH8D28-4R7
10µF ±10%, 25V X5R
ceramic capacitor (1206)
M ur ata GRM 31C R61E 106KA
4.7µF ±10%, 50V X7R
ceramic capacitor (1210)
(1x)
Murata GRM32ER71H475K
60V , 6A n- channel M O S FE T
( P ow er P AK 1212- 8)
Vishay Si7308DN
3A, 60V Schottky diode
Nihon EC31QS06
40mΩ ±1%, 1/2W
IRC LRC-LRF-1206LF-01-
R040-F
FIGURE 1
Design Procedure
750kHz
3.2V (typ), 3.5V (max) at
20mA
Nichia NSSW008C
6 series x 6 parallel,
20mA (max)
2.8V to 5.5V, V
0.9µH , 4.7A p ow er i nd uctor
Sumida CDRH5D16-0R9
10µF ±10%, 10V X5R
ceramic capacitor (1206)
M ur ata GRM 31M R61A106K
2.2µF ±10%, 50V X7R
ceramic capacitor (1x)
Murata GRM31CR71H225K
30V, 4.9A n-channel
MOSFET (6-pin TSOP)
Vishay Si3456BDV
3A, 30V Schottky diode
Nihon EC31QS03L
30mΩ ±1%, 1/2W
IRC LRC-LRF-1206LF-01-
R030-F
Thermal Shutdown
FIGURE 3
CC
= 5V