MAX8901A MAXIM [Maxim Integrated Products], MAX8901A Datasheet - Page 7

• Manufacturer Part Number: MAX8901A
• Description: Highest Efficiency Supply for 2 to 6 Series WLEDs in a 2mm x 2mm TDFN Package
• Manufacturer: MAXIM [Maxim Integrated Products]

Series WLEDs in a 2mm x 2mm TDFN Package
PIN
—
1
2
3
4
5
6
7
8
NAME
PGND
COMP
GND
OVP
ON
_______________________________________________________________________________________
CS
LX
EP
IN
WLED Overvoltage Protection Input. OVP monitors voltage at the WLEDs. Connect OVP to the
positive terminal of the output capacitor. If an OVP condition is detected, the MAX8901_ latches off.
Cycle V
Enable and Dimming Control Input. Drive ON high to enable the IC. Drive ON low for greater than
1.33ms (typ) to shutdown the WLED current regulator.
For the MAX8901A: After V
and increases the WLED current to full brightness. Apply a minimum 30kHz (500kHz max) PWM
signal to ON to adjust the WLED brightness from 100% to off, proportional to the duty cycle of the
PWM signal. See the PWM Dimming Control (MAX8901A) section for more details.
For the MAX8901B: After ON is driven high for 40µs (min), the MAX8901B enters soft-start and
increases the WLED current to full brightness. Subsequent pulses on ON cause the MAX8901B
WLED current to decrease in 32 equal steps. See the Serial-Pulse Dimming Control (MAX8901B)
section for more details.
Power Supply Input. Bypass IN to GND with a 1µF ceramic capacitor placed as close as possible to
the IC. If V
switching and no WLED current flows (if the forward voltage of the WLED string is greater than V
When V
initiated and normal operation
Boost Inductor Node. Connect an inductor between IN and LX. LX is high impedance in shutdown.
Power Ground. Connect to GND and the exposed paddle (EP) with a short, wide trace.
Analog Ground. Connect GND to the exposed paddle with a short, wide trace.
WLED Boost Compensation Node. Connect a 0.022µF ceramic capacitor from COMP to GND.
C
shutdown.
WLED Current Sense Input. For the MAX8901A, connect a current-sense resistor from CS to GND.
Voltage sensed at CS regulates the WLED current. For the MAX8901B, do not connect a sense
resistor from CS to GND. The MAX8901B provides an internal current source from CS to GND to
program the WLED current. The MAX8901B regulates V
regulates V
Exposed Metal Paddle. Connect EP to GND. For good thermal dissipation, the exposed paddle must
be connected to a large ground plane.
COMP
Highest Efficiency Supply for 2 to 6
IN
IN
stabilizes the converter and sets the soft-start time. COMP discharges to GND when in
or toggle V
falls below the overvoltage lockout hysteresis level (6.0V min, V
IN
CS
exceeds the input overvoltage lockout threshold (6.5V max, V
to 0.5V (typ) for maximum duty cycle only.
ON
to restart the IC.
IN
is above V
resumes.
UVLO
FUNCTION
and ON is driven high, the MAX8901A enters soft-start
CS
to 0.5V (typ) for all I
IN
IN
Pin Description
falling), soft-start is
rising), the IC stops
LED.
The MAX8901A
IN
).
7