MAX1986ETE+T Maxim Integrated Products, MAX1986ETE+T Datasheet - Page 11

• 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 standard application circuit of the MAX1984 drives
eight white LEDs (Figure 1). The standard application cir-
cuit of the MAX1985 drives six white LEDs (Figure 6). The
standard application circuit of the MAX1986 drives four
white LEDs (Figure 7). The input voltage range is from
2.7V to 5.5V. Table 1 lists the recommended component
options and Table 2 lists the component suppliers.
The MAX1984/MAX1985/MAX1986 are white LED dri-
vers that use individual regulators to control the current
of up to eight LEDs. A high-efficiency step-up regulator
generates just enough voltage to keep all the current
regulators in regulation. A versatile dimming interface
accommodates analog, DPWM, or parallel control.
Good LED current matching is achieved using individ-
ual current regulators for each LED (Figure 3). The reg-
ulator is an analog gain block with an open-drain
N-channel MOSFET output stage and can sink up to
Table 1. Component List
*MAX1984 and MAX1985 only.
**MAX1984 only.
Table 2. Component Suppliers
Nichia
Sumida
Taiyo Yuden
TDK
D1–D4, D5*, D6*,
DESIGNATION
D7**, D8**
C1, C4
L1
Standard Application Circuits
SUPPLIER
______________________________________________________________________________________
2 x 2.2µF, 6.3V X5R ceramic
capacitors (0603)
Taiyo Yuden JMK107BJ225MA
TDK C1608X5ROJ225K
Surface-mount white LEDs
Nichia NSCW215T
10µH, 1A inductor
Sumida CLS5D11HP-100NC
Detailed Description
LED Current Regulators
MAX1984
717-285-2323
847-545-6700
800-348-2496
847-803-6100
PHONE
Ultra-High-Efficiency White
2 x 2.2µF, 6.3V X5R ceramic
capacitors (0603)
Taiyo Yuden JMK107BJ225MA
TDK C1608X5ROJ225K
15µH, 0.85A inductor
Sumida CLS5D11HP-150NC
25mA LED current. The LED current is sensed using an
internal 1Ω resistor connected between the source of
the MOSFET and ground. The regulator controls the
output current by comparing the voltage across the
current-sense resistor with a reference voltage (IREF)
set by the dimming control circuitry.
The step-up converter is regulated at a voltage just
high enough to power the LEDs. Since the forward volt-
age is different for each LED, the LED with the largest
forward voltage sets the regulation voltage. Each cur-
rent regulator’s voltage drop (from LD_ to LDG) is moni-
tored and the lowest voltage drop is used as the
step-up regulator’s feedback.
At startup, it is important to ensure the output voltage
rises high enough to forward bias all LEDs and allow their
current regulators to detect their presence. Therefore,
before the current regulators are enabled the step-up
regulator output is made to rise up to the OUT OVP
threshold (5.3V, typ). Then, the step-up regulator stops
switching and each current regulator output is tested
DESCRIPTION
MAX1985
717-285-9378
847-545-6720
847-925-0899
847-390-4405
FAX
22µH, 0.65A inductor
Sumida CLS5D11HP-220NC
2.2µF, 6.3V X5R ceramic
capacitors (0603)
Taiyo Yuden JMK107BJ225MA
TDK C1608X5ROJ225K
Startup and Feedback
LED Drivers
www.nichia.com
www.sumida.com
www.t-yuden.com
www.component.tdk.com
MAX1986
WEBSITE
11