MAX16831ATJ+T Maxim Integrated Products, MAX16831ATJ+T Datasheet - Page 13

• 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

capacitor to hold the charge when the DIM signal has
turned off the gate drive. When DIM is high again, the
voltage on the compensation capacitors, C1 and C2,
will force the converter into steady-state instantaneously.
PWM dimming is achieved by driving DIM with either a
PWM signal or a DC signal. The PWM signal is internal-
ly connected to the error amplifier, the dimming
MOSFET gate driver, and the switching MOSFET gate
driver. When the DIM signal is high, the dimming
MOSFET and the switching MOSFET drivers are
enabled and the output of the voltage-error amplifier is
connected to the external compensation network. Also,
the buffered current-sense signal is connected to CS.
Preventing discharge of the compensation capacitor
when the DIM signal is low will allow the control loop to
return the LED current to its original value almost
instantaneously.
When the DIM signal goes low, the output of the error
amplifier is disconnected from the compensation net-
work and the voltage of compensation capacitors, C1
and C2 is preserved. Choose low-leakage capacitors
for C1 and C2. The drivers for the external dimming
and switching MOSFETs are disabled, and the convert-
er stops switching. The inductor energy is now trans-
ferred to the output capacitors.
When the DIM signal goes high and the gate drivers are
enabled, the additional voltage on the output capacitor
may cause a current spike on the LED string. A larger
output capacitor will result in a smaller current spike. The
MAX16831 thus achieves fast PWM dimming response.
The MAX16831 features built-in overvoltage protection,
overcurrent protection, HICCUP mode current-limit pro-
tection, and thermal shutdown. Overvoltage protection
is achieved by connecting OV to HI through a resistive
voltage-divider. HICCUP mode limits the power dissi-
pation in the external MOSFETs during severe fault
conditions. Internal thermal shutdown protection safely
turns off the converter when the junction temperature
exceeds +165°C.
The overvoltage protection (OVP) comparator com-
pares the voltage at OV with a 1.235V (typ) internal ref-
erence. When the voltage at OV exceeds the internal
reference, the OVP comparator terminates PWM
switching and no further energy is transferred to the
High-Voltage, High-Power LED Driver with
______________________________________________________________________________________
Overvoltage Protection
Analog and PWM Dimming Control
Fault Protection
PWM Dimming
load. The MAX16831 re-initiates soft-start once the
overvoltage condition is removed. Connect OV to HI
through a resistive voltage-divider to set the overvolt-
age threshold at the output.
Connect OV to HI or to the high-side of the LEDs
through a resistive voltage-divider to set the overvolt-
age threshold at the output (Figure 4). The overvoltage
protection (OVP) comparator compares the voltage at
OV with a 1.235V (typ) internal reference. Use the fol-
lowing equation to calculate resistor values:
where V
and R
vent discharge of filter capacitors. This will prevent
unnecessary undervoltage and overvoltage conditions
during dimming.
The MAX16831 features load-dump protection up to
80V. LED drivers using the MAX16831 can sustain sin-
gle fault load dump events. Repeated load dump events
within very short time intervals can cause damage to the
dimming MOSFET due to excess power dissipation.
The MAX16831 contains an internal temperature sensor
that turns off all outputs when the die temperature
exceeds +165°C. Outputs are enabled again when the
die temperature drops below +145°C.
Figure 4. Setting the Overvoltage Threshold
OV2
V
OV
LED+
to be reasonably high-value resistors to pre-
R
R
R
is the 1.235V OV threshold. Choose R
OV1
OV2
OV
1
=
R
Setting the Overvoltage Threshold
OV
2
OV
×
⎛
⎜
⎝
V
OV LIM
MAX16831
Load-Dump Protection
AGND
_
V
OV
Thermal Shutdown
-
V
OV
⎞
⎟
⎠
OV1
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