MAX16812ATI+T Maxim Integrated Products, MAX16812ATI+T Datasheet - Page 12

• Manufacturer Part Number: MAX16812ATI+T
• Description: IC LED DRIVR HIGH BRIGHT 28-TQFN
• Manufacturer: Maxim Integrated Products
• Type: HBLED Driverr

Specifications of MAX16812ATI+T

• Constant Current: Yes
• Topology: PWM, SEPIC, Step-Down (Buck), Step-Up (Boost)
• Number Of Outputs: 1
• Internal Driver: Yes
• Type - Primary: Automotive
• Type - Secondary: High Brightness LED (HBLED)
• Frequency: 125kHz ~ 500kHz
• Voltage - Supply: 5.5 V ~ 76 V
• Mounting Type: Surface Mount
• Package / Case: 28-TQFN Exposed Pad
• Operating Temperature: -40°C ~ 125°C
• Internal Switch(s): Yes
• Number Of Segments: 2
• Low Level Output Current: 80 uA
• High Level Output Current: 300 uA
• Operating Supply Voltage: 5.5 V to 76 V
• Maximum Power Dissipation: 2759 mW
• Maximum Operating Temperature: + 125 C
• Mounting Style: SMD/SMT
• Minimum Operating Temperature: - 40 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Voltage - Output: -
• Current - Output / Channel: -
• Efficiency: -
• Lead Free Status / Rohs Status: Details

Integrated High-Voltage LED Driver
with Analog and PWM Dimming Control
The MAX16812 offers analog dimming of the LED cur-
rent by allowing the application of an external voltage
at REFI. The output current is proportional to the volt-
age at REFI. Use a potentiometer from REF or directly
apply an external voltage source at REFI.
The PWM comparator uses the instantaneous switch
current, the error-amplifier output, and the slope com-
pensation to determine when the gate drive DRV to the
internal n-channel switching MOSFET turns off. In nor-
mal operation, gate drive DRV to the n-channel MOS-
FET turns off when:
where I
switching MOSFET, R
resistor, V
amplifier, V
V
at zero and slews at the programmed slew rate (SR).
The current-sense resistor (R
the source of the internal MOSFET and ground, sets the
current limit. The SRC input has a voltage trip level
(V
the following equation to calculate the value of R
where I
switching MOSFET at full load and low line. When the
Figure 6. OVP Setting
12
BE
SRC
Internal Switching MOSFET Current Limit
______________________________________________________________________________________
drop, and V
) of 600mV for the cycle-by-cycle current limit. Use
I
SW
LXLIM
SW
COMP
x R
is the current through the internal n-channel
OFFSET
is the peak current that flows through the
SRC
SCOMP
is the output voltage of the internal
V
≥ V
R
is the internal DC offset, which is a
LED+
R
R
OV1
OV2
SRC
COMP
SRC
is the ramp function that starts
=
is the switch current-sense
- V
I
HV
OV
LXLIM
SRC
V
SRC
OFFSET
MAX16812
PWM Comparator
), connected between
AGND
Analog Dimming
- V
SCOMP
SRC
:
voltage produced by this current (through the current-
sense resistor) exceeds the current-limit (ILIM) com-
parator threshold, the MOSFET driver (DRV) quickly
terminates the current on-cycle. The 200ns leading-
edge blanking circuit suppresses the leading-edge
spike on the current-sense waveform from appearing at
the current-limit comparator. There is also a hiccup
comparator (HICCUP) that limits the peak current in the
internal switch set at twice the peak limit setting.
L_REG provides power for the DRV output. Connect a
resistor from DRV to gate GT of the internal switching
MOSFET to control the switching MOSFET rise and fall
times, if necessary.
DGT is the gate drive to the external dimming MOSFET
referenced to LV. H_REG provides the power to the
gate drive.
The overvoltage protection (OVP) comparator com-
pares the voltage at OV with a 1.238V (typ) internal ref-
erence. When the voltage at OV exceeds the internal
reference, the OVP comparator terminates PWM switch-
ing and no further energy is transferred to the load.
Connect OV to HV through a resistive voltage-divider to
ground to set the overvoltage threshold at the output.
Connect OV to HV or to the high-side of the LEDs
through a resistive voltage-divider to set the overvolt-
age threshold at the output (Figure 6).
Setting the Overvoltage Threshold
R
R
OV1
OV2
Switching MOSFET Driver (DRV)
V
LED+
OV
MOSFET Gate Drive (DGT)
MAX16812
Overvoltage Protection
AGND
Internal n-Channel
External Dimming