MAX1986ETE+T Maxim Integrated Products, MAX1986ETE+T Datasheet - Page 14

• Manufacturer Part Number: MAX1986ETE+T
• Description: IC LED DRVR WHITE BCKLGT 16-TQFN
• Manufacturer: Maxim Integrated Products
• Type: Backlight, White LEDr

Specifications of MAX1986ETE+T

• Topology: PWM, Step-Up (Boost)
• Number Of Outputs: 4
• Internal Driver: Yes
• Type - Primary: Backlight
• Type - Secondary: White LED
• Frequency: 800kHz ~ 1.2MHz
• Voltage - Supply: 2.7 V ~ 5.5 V
• Mounting Type: Surface Mount
• Package / Case: 16-TQFN Exposed Pad
• Operating Temperature: -40°C ~ 85°C
• Current - Output / Channel: 25mA
• Internal Switch(s): Yes
• Efficiency: 90%
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Voltage - Output: -
• Lead Free Status / Rohs Status: Details

The MAX1984/MAX1985/MAX1986 provide a control
input (SEL) to selectively turn on one subset, the other
subset, or all of the LEDs. SEL is a three-level logic
input that can be connected to logic low, logic high, or
left unconnected. Table 5 is the truth table.
Connecting SETI to ground enables the LED test mode.
In this mode, the LED current is set to 0.5mA and
DC-to-DC switching is inhibited. OUT is powered from
IN through an internal silicon diode.
Forcing 0.5mA through the LED is a simple way to
determine whether the diode has suffered any ESD
damage. LEDs that do not light in this mode usually
have suffered ESD or other damage. The dimming con-
trol inputs are ignored in the test mode.
Ultra-High-Efficiency White
LED Drivers
Table 3. 3-Bit Parallel Control Truth Table
Table 4. 2-Bit Parallel Control Truth Table
Table 5. SEL Control Truth Table
14
Low (V
Mid (SEL unconnected
or 0.5V < V
High (V
BITA
BITA
0
0
1
1
0
0
0
0
1
1
1
1
______________________________________________________________________________________
SEL
SEL
BITB BITC
BITB
SEL
0
1
0
1
0
0
1
1
0
0
1
1
< 0.4V)
SEL
> 2.05V)
< 1.8V)
BITC
0
0
0
0
0
1
0
1
0
1
0
1
BRIGHTNESS (%)
BRIGHTNESS (%)
MAX1984
LED5 ON
LED8 ON
LED1 to
LED6 to
33.3
66.7
100
14.3
26.6
42.9
57.1
71.4
85.7
100
0
0
All LEDs ON
MAX1985
LED4 ON
LED6 ON
LED1 to
LED5 to
LED Test Mode
LED Selection
Full-scale current
Full-scale current
Minimum current
Minimum current
COMMENTS
COMMENTS
set by SETI
set by SETI
Shutdown
Shutdown
MAX1986
—
LED3 ON
LED4 ON
—
—
—
—
—
LED1 to
As soon as the input voltage rises above the UVLO
threshold and the internal reference is ready, the step-
up regulator starts unless the device is in shutdown. If a
2-bit or 3-bit parallel control is used, the MAX1984/
MAX1985/MAX1986 enter shutdown mode when BITA,
BITB, and BITC are logic low. The parts come out of
shutdown if at least 1 bit is logic high. If DPWM control
is used, the parts enter shutdown mode when the duty
cycle of BITA is less than 5% (typ) and BITC is logic
low. If analog control is used, the parts enter shutdown
when the voltages on both BITA and BITB are logic low.
Output OVP prevents the internal switches from being
damaged if all LEDs are open. If the output voltage
rises above OUT OVP rising threshold, the
MAX1984/MAX1985/MAX1986 turn off the step-up reg-
ulator. Once the output voltage falls below OVP falling
threshold, the step-up regulator turns on again.
The MAX1984/MAX1985/MAX1986’s 1MHz switching
frequency allows the use of low-profile surface-mount
inductors. The MAX1984 works well with a 10µH induc-
tor, the MAX1985 works well with a 15µH inductor, and
the MAX1986 works well with a 22µH inductor. The
inductor saturation current rating should be higher than
the N-channel switch current limit. For high efficiency,
choose an inductor made of high-frequency core mate-
rial to reduce core losses. Using a shielded inductor
reduces radiated EMI.
The output capacitor affects the circuit’s stability and
output-voltage ripple. The MAX1984 works well with a
4.7µF ceramic output capacitor, the MAX1985 works
well with a 3.3µF ceramic output capacitor, and the
MAX1986 works well with a 2.2µF ceramic output
capacitor. Always use capacitors with working voltage
ratings higher than the output OVP rising threshold
(5.5V max).
Applications Information
Output Capacitor Selection
Overvoltage Protection
Inductor Selection
Shutdown