MAX16838ATP/V+ Maxim Integrated, MAX16838ATP/V+ Datasheet - Page 14

• Manufacturer Part Number: MAX16838ATP/V+
• Description: LED Lighting Drivers Integrated 2-Channel High-Brightness LED Drivers with High-Voltage DC-DC Controller
• Manufacturer: Maxim Integrated

Specifications of MAX16838ATP/V+

• Input Voltage: 4.75 V to 40 V
• Maximum Supply Current: 3.1 mA
• Power Dissipation: 2051 mW

Integrated, 2-Channel, High-Brightness LED Driver
with High-Voltage Boost and SEPIC Controller
Figure
Connect a 4.7I resistor from V
rest of the chip from the V
regulator. Bypass DRV to PGND with a minimum of 1FF
ceramic capacitor as close as possible to the device. For
input voltage range of 4.5V to 5.5V, connect IN to V
The MAX16838 features two identical constant-current
sources used to drive multiple HB LED strings. The
current through each of the channels is adjustable
between 20mA and 150mA using an external resistor
(R
R
where I
channels in amps.
For single-channel operation, connect channel 1 and
channel 2 together. See Figure 2.
The MAX16838 features LED brightness control using an
external PWM signal applied at DIM. The device accepts
a minimum pulse width of 1Fs. Therefore, a 5000:1 dim-
ming ratio is achieved when using a PWM frequency of
200Hz. Drive DIM high to enable both LED current sinks
and drive DIM low to disable both LED current sinks.
14
ISET
ISET
_____________________________________________________________________________________
2. Configuration for Higher LED String Current
) connected between ISET and SGND. Select
using the following formula:
OUT_
is the desired output current for both
MAX16838
R
ISET
LED Current Control (ISET)
CONVERTER
OUTPUT
=
BOOST
OUT1
OUT2
I
OUT _
1512
CC
LED Dimming Control
CC
pin with the 5V internal
( )
Ω
to DRV to power the
40mA TO 300mA
CC
.
The duty cycle of the PWM signal applied to DIM also
controls the DC-DC converter’s output voltage. If the
turn-on duration of the PWM signal is less than five
oscillator clock cycles, then the boost converter regu-
lates its output based on feedback from the OV input.
During this mode, the converter output voltage is regu-
lated to 95% of the OV threshold voltage. If the turn-on
duration of the PWM signal is greater than or equal to
six oscillator clock cycles, then the converter regulates
its output such that the minimum voltage at OUT_ is 1V.
The MAX16838 fault protections include cycle-by-cycle
current limiting, DC-DC converter output overvoltage
protection, open-LED detection, short-LED detection,
and overtemperature detection. An open-drain LED fault
flag output (FLT) goes low when an open-LED/short-LED
or overtemperature condition is detected.
The MAX16838 monitors the drains of the current sinks
(OUT_) to detect any open string. If the voltage at
any output falls below 300mV and the OV threshold is
triggered (i.e., even with OUT_ at the OV voltage the
string is not able to regulate above 300mV), then the
MAX16838 interprets that string to be open, asserts FLT,
and disconnects that string from the operation loop. The
MAX16838 features an adjustable overvoltage threshold
input (OV). Connect a resistor-divider from the switching
converter output to OV and SGND to set the overvoltage
threshold level. Use the following formula to program the
overvoltage threshold:
The MAX16838 features a two-level short-LED detection
circuitry. If a level 1 short is detected on any one of the
strings, FLT is asserted. A level 1 short is detected if
the difference between the total forward LED voltages
of the two strings exceeds 4.2V (typ). If a level 2 short
is detected on any one of the strings, the particular LED
string with the short is turned off after 6Fs and FLT is
asserted. A level 2 short is detected if the difference
between the total forward LED voltages of the two strings
exceeds 7.8V (typ). The strings are reevaluated on each
DIM rising edge and FLT is deasserted if the short is
removed.
Open-LED Management and Overvoltage Protection
V
OV
=
1.23V
×



1
+
R2
Fault Protections
R1
Short-LED Detection
OV
OV


