MAX16831ATJ+T Maxim Integrated Products, MAX16831ATJ+T Datasheet - Page 11

• Manufacturer Part Number: MAX16831ATJ+T
• Description: IC LED DRIVR HIGH BRIGHT 32-TQFN
• Manufacturer: Maxim Integrated Products
• Type: HBLED Driverr

Specifications of MAX16831ATJ+T

• Topology: PWM, Step-Down (Buck), Step-Up (Boost)
• Number Of Outputs: 1
• Internal Driver: No
• Type - Primary: Automotive
• Type - Secondary: High Brightness LED (HBLED), RGB
• Frequency: 125kHz ~ 600kHz
• Voltage - Supply: 5.5 V ~ 76 V
• Mounting Type: Surface Mount
• Package / Case: 32-TQFN Exposed Pad
• Operating Temperature: -40°C ~ 125°C
• Internal Switch(s): Yes
• Efficiency: 90%
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Voltage - Output: -
• Current - Output / Channel: -
• Lead Free Status / Rohs Status: Details

The MAX16831 includes a 5% accurate 3V (typ)
buffered reference output, REF. REF is a push-pull out-
put capable of sourcing/sinking 100µA of current and
can drive a maximum load capacitance of 100pF.
Connect REF to DIM through a resistive voltage-divider
to supply an analog signal for dimming. See the
Dimming Input (DIM) section.
The MAX16831 requires an external n-channel
MOSFET for PWM dimming. Connect the MOSFET to
the output of the DDR dimming driver, DGT, for normal
operation. V
DDR dimming driver is capable of sinking or sourcing
up to 20mA of current. The average current required to
drive the dimming MOSFET (I
the MOSFET’s total gate charge (Q
ming frequency of the converter, f
ing equation to calculate the average gate drive current
for the n-channel dimming FET.
The MAX16831 drives an external n-channel MOSFET.
Use an external supply or connect REG2 to DRI to
power the MOSFET driver. The driver output, V
swings between ground and V
remains below the absolute maximum V
external MOSFET. DRV is capable of sinking 2.5A or
sourcing 1.4A of peak current, allowing the MAX16831
to switch MOSFETs in high-power applications. The
average current sourced to drive the external MOSFET
depends on the total gate charge (Q
frequency of the converter, f
in the MAX16831 is a function of the average output
drive current (I
calculate the power dissipation in the gate driver sec-
tion of the MAX16831 due to I
where V
I
exceed 20mA.
The dimming input, DIM, functions with either analog or
PWM control signals. Once the internal pulse detector
detects three successive edges of a PWM signal with a
frequency between 80Hz and 2kHz, the MAX16831 syn-
chronizes to the external signal and pulse-width-modu-
lates the LED current at the external DIM input frequency
with the same duty cycle as the DIM input. If an analog
CC
is the operating supply current. I
n-Channel MOSFET Switch Driver (DRV)
DRI
is the supply voltage to the gate driver and
DGT
I
DRIVE_DIM
High-Voltage, High-Power LED Driver with
P
DRIVE
Dimming MOSFET Driver (DDR)
D
swings between V
= (I
______________________________________________________________________________________
I
DRIVE
). Use the following equations to
DRIVE
Reference Voltage Output
= Q
= Q
+ I
SW
G_DIM
Dimming Input (DIM)
DRIVE
G
CC
DRIVE_DIM
x f
. The power dissipation
DRI
) x V
Analog and PWM Dimming Control
SW
DIM
:
G_DIM
LO
x f
. Ensure that V
DRI
DIM
G
DRIVE
. Use the follow-
and V
) and operating
GS
) and the dim-
) depends on
rating of the
should not
CLMP
. The
DRV
DRI
,
control signal is applied to DIM, the MAX16831 com-
pares the DC input to an internally generated 200Hz
ramp to pulse-width-modulate the LED current (f
200Hz). The output current duty cycle is linearly
adjustable from 0 to 100% (0.2V < V
Use the following formula to calculate the voltage, V
necessary for a given output-current duty cycle, D:
where V
Connect DIM to REF through a resistive voltage-divider
to apply a DC DIM control signal (Figure 2). Use the
required dimming input voltage, V
above and select appropriate resistor values using the
following equation:
where V
30kΩ ≤ R
For proper operation at startup or after toggling ENABLE,
the controller needs three clock edges or an analog volt-
age greater than 0.3V on the DIM input.
The MAX16831 is capable of stand-alone operation or
synchronizing to an external clock, and driving external
devices in SYNC mode. For stand-alone operation, pro-
gram the switching frequency by connecting a single
external resistor, R
Select the switching frequency, f
600kHz and calculate R
where the switching frequency is in kHz and RT is in kΩ.
The MAX16831 is also capable of synchronizing to an
external clock signal ranging from 125kHz to 600kHz.
Figure 2. Creating a DIM Input Signal from REF
Oscillator, Clock, and Synchronization
DIM
REF
3
+ R
R
R
is the voltage applied to DIM in volts.
3
4
R
is the 3V reference output voltage and
4
4
= R
V
≤ 150kΩ.
DIM
3
T
R
x V
, between RTSYNC and ground.
= (D x 2.6) + 0.2V
T
DIM
REF
T
=
DIM
using the following formula:
500
f
/ (V
SW
MAX16831
kHz
AGND
REF
×
SW
DIM
- V
25 Ω
, from 125kHz to
DIM
DIM
k
< 2.8V).
)
, calculated
DIM
DIM
11
=
,