MAX8790AETP+T Maxim Integrated Products, MAX8790AETP+T Datasheet - Page 12

• 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

The MAX8790A’s fixed-frequency, current-mode, step-
up controller automatically chooses the lowest active
FB_ voltage to regulate the feedback voltage.
Specifically, the difference between the lowest FB_ volt-
age and the current source-control signal plus an offset
(V
error signal is compared to the external switch current
plus slope compensation to terminate the switch on-
time. As the load changes, the error amplifier sources
or sinks current to the CCV output to adjust the
required peak inductor current. The slope-compensa-
tion signal is added to the current-sense signal to
improve stability at high duty cycles.
At light loads, the MAX8790A automatically skips pulses
to improve efficiency and prevent overcharging the out-
put capacitor. In SKIP mode, the inductor current ramps
up for a minimum on-time of approximately 150ns, then
discharges the stored energy to the output. The switch
remains off until another pulse is needed to boost the
output voltage.
Six-String White LED Driver with Active
Current Balancing for LCD Panel Applications
Figure 3. Low-Input-Voltage Application Circuit
12
SAT
5V SUPPLY
EXTERNAL
______________________________________________________________________________________
511kΩ
) is integrated at the CCV output. The resulting
2.8V TO 5.5V
Fixed-Frequency Step-Up Controller
V
IN
C
0.1μF
0.1μF
IN
1.2kΩ
1μF
N.C.
SHDN
ENA
ISET
BRT
FSET
OSC
CCV
CPLL
EP
V
CC
MAX8790A
IN
0.9μH
L1
GND
EXT
FB2
FB3
FB4
FB5
FB6
FB1
CS
OV
N1
The MAX8790A includes an internal low-dropout linear
regulator (V
SHDN is high, this linear regulator generates a 5V sup-
ply to power an internal PWM controller, control logic,
and MOSFET driver. This linear regulator can deliver at
least 10mA of total additional load current. If V
than or equal to 5.5V, V
together and powered from an external 5V supply.
There is an internal diode from V
be greater than V
The MAX8790A includes UVLO protection. The controller
is disabled until V
4.25V (typ). Hysteresis on UVLO is approximately 20mV.
The V
greater ceramic capacitor.
R
30mΩ
R2
59kΩ
S
D1
C
1MΩ
OUT
R1
CC
pin should be bypassed to GND with a 1µF or
CC
). When V
CC
CC
Internal 5V Linear Regulator
(see Figure 2).
exceeds the UVLO threshold of
CC
IN
and IN can be connected
is higher than 5.5V and
CC
UP TO 22V
V
OUT
V
to IN, so V
CC
and UVLO
IN
IN
is less
must