MAX16814ATP+ Maxim Integrated Products, MAX16814ATP+ Datasheet - Page 14

• Manufacturer Part Number: MAX16814ATP+
• Description: LED Drivers Integrated 4-Channel High-Brightness LED
• Manufacturer: Maxim Integrated Products

Specifications of MAX16814ATP+

• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Integrated, 4-Channel, High-Brightness LED
Driver with High-Voltage DC-DC Controller
where R
The pulse width for the synchronization pulse should
satisfy the following relations:
where t
t
programmed clock period, and
pulse voltage level.
The internal LDO regulator converts the input voltage
at IN to a 5V output voltage at V
supplies up to 50mA current to provide power to internal
control circuitry and the gate driver. Connect a resistor
between V
the recommended value is 4.7I. Bypass DRV with a
capacitor to PGND. The external resistor and bypass
capacitor provide noise filtering. Bypass V
with a minimum of 1FF ceramic capacitor as close to the
device as possible.
The NDRV output is a push-pull output with the on-resis-
tance of the pMOS typically 1.1I and the on-resistance
of the nMOS typically 0.9I. NDRV swings from PGND to
DRV to drive an external n-channel MOSFET. The driver
typically sources 2.0A and sinks 2.0A allowing for fast
turn-on and turn-off of high gate-charge MOSFETs.
The power dissipation in the MAX16814 is mainly a func-
tion of the average current sourced to drive the external
MOSFET (I
I
ing frequency of the converter. Connect DRV to V
a 4.7I resistor to power the gate driver with the internal
5V regulator.
The MAX16814 features four identical constant-current
sources used to drive multiple HB LED strings. The cur-
rent through each one of the four channels is adjustable
between 20mA and 150mA using an external resistor
(R
R
14
CLK
DRV
SETI
SETI
_____________________________________________________________________________________
depends on the total gate charge (Q
is the synchronization clock time period, t
using the following formula:
) connected between SETI and SGND. Select
PW
T
is in Ω.
CC
DRV
is the synchronization source pulse width,



t
t
and DRV to power the gate-drive circuitry;
t
0.8
PW
CLK
PW
) if there are no additional loads on V
−
<
V
t
t
S
t
CLK
PW
CLK
t
<
CI
0.5
V
(
S
t
CI



+
V
−
LED Current Control
5V LDO Regulator (V
V
S
1.05 t
S
CC
is the synchronization
PWM MOSFET Driver
>
3.4
. The LDO regulator
×
CLK
G
)
) and operat-
CC
to SGND
CI is the
CC
with
CC
CC
)
.
Figure 4. Configuration for Higher LED String Current
where I
four channels.
If more than 150mA is required in an LED string, use two
or more of the current source outputs (OUT_) connected
together to drive the string as shown in Figure 4.
The MAX16814 features LED brightness control using an
external PWM signal applied at DIM. A logic-high signal
on the DIM input enables all four LED current sources
and a logic-low signal disables them.
For the MAX16814A_ _ and the MAX16814U_ _, 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 5 oscillator clock cycles
(DIM pulse width decreasing) then the boost converter
regulates its output based on feedback from the OVP
input. During this mode, the converter output voltage
is regulated to 95% of the OVP threshold voltage. If
the turn-on duration of the PWM signal is greater than
or equal to 6 oscillator clock cycles (DIM pulse width
increasing), then the converter regulates its output so
that the minimum voltage at OUT_ is 1V.
Fault protections in the MAX16814 include cycle-by-
cycle current limiting using the PWM controller, DC-DC
converter output overvoltage protection, open-LED
detection, short LED detection and protection, and
overtemperature shutdown. An open-drain LED fault
OUT_
MAX16814
is the desired output current for each of the
BOOST CONVERTER
R
SETI
OUTPUT
OUT1
OUT2
OUT3
OUT4
=
1500 I
LED Dimming Control
OUT_
Fault Protections
40mA TO 300mA
PER STRING