MAX16833AUE/V+T Maxim Integrated Products, MAX16833AUE/V+T Datasheet - Page 16

• Manufacturer Part Number: MAX16833AUE/V+T
• Description: IC HB LED DVR CURR SENSE 16TSSOP
• Manufacturer: Maxim Integrated Products

Specifications of MAX16833AUE/V+T

• Topology: Flyback, Low Side, PWM, SEPIC, Step-Down (Buck), Step-Up (Boost)
• Number Of Outputs: 1
• Internal Driver: No
• Type - Primary: Automotive, General Purpose
• Type - Secondary: High Brightness LED (HBLED)
• Frequency: 100kHz ~ 1MHz
• Voltage - Supply: 5 V ~ 65 V
• Mounting Type: Surface Mount
• Package / Case: 16-TSSOP (0.173", 4.40mm Width) Exposed pad
• Operating Temperature: -40°C ~ 125°C
• Current - Output / Channel: 3A
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Voltage - Output: -
• Lead Free Status / Rohs Status: Details

High-Voltage HB LED Drivers with
Integrated High-Side Current Sense
Slope compensation should be added to converters
with peak current-mode control operating in continuous-
conduction mode with more than 50% duty cycle to
avoid current-loop instability and subharmonic oscilla-
tions. The minimum amount of slope compensation that
is required for stability is:
In the ICs, the slope-compensating ramp is added to the
current-sense signal before it is fed to the PWM com-
parator. Connect a resistor (R1) from CS to the inductor
current-sense resistor terminal to program the amount of
slope compensation.
The ICs generate a current ramp with a slope of 50FA/
t
forced into the external resistor (R1) connected between
CS and the source of the external MOSFET, thereby
adding a programmable slope compensating voltage
(V
The minimum value of the slope-compensation voltage
that needs to be added to the current-sense signal at
peak current and at minimum line voltage is:
where f
mum duty cycle, which occurs at low line, V
minimum input voltage, and L
the selected inductor. For adequate margin, the slope-com-
pensation voltage is multiplied by a factor of 1.5. Therefore,
the actual slope-compensation voltage is given by:
From the previous formulas, it is possible to calculate the
value of R4 as:
For boost configuration:
16
OSC
SC
SCOMP
SC
MIN
_____________________________________________________________________________________
for slope compensation. The current-ramp signal is
V
MIN
SW
SCMIN
=
) at the current-sense input CS. Therefore:
R4
(D
=
dV
is the switching frequency, D
(D
inductor current upslope) x R4
MAX
=
SC
= 0.5 (inductor current downslope -
IL
MAX
/dt = (R1 x 50FA)/t
P
×
2 L
+
(V
×
×
V
0.75D
2 L
SC
(V
LED
×
MIN
LED
= 1.5SC
MIN
- V
MAX
×
0.418V
- 2V
INMIN
f
MIN
SW
×
Slope Compensation
V
f
INMIN
SW
LED
MIN
is the minimum value of
) R4)
L
OSC
×
MIN SW
−
) R4)
2V
×
f
in V/s
MAX
INMIN
(V)Buck-boost
(V) Boost
INMIN
is the maxi-
is the
For buck-boost configuration:
The minimum value of the slope-compensation resistor
(R1) that should be used to ensure stable operation at
minimum input supply voltage can be calculated as:
For boost configuration:
For buck-boost configuration :
where f
is the minimum input voltage in volts, V
voltage in volts, D
is the peak inductor current in amperes, and L
minimum value of the selected inductor in henries.
The function of the output capacitor is to reduce the
output ripple to acceptable levels. The ESR, ESL, and
the bulk capacitance of the output capacitor contribute
to the output ripple. In most applications, the output ESR
and ESL effects can be dramatically reduced by using
low-ESR ceramic capacitors. To reduce the ESL and
ESR effects, connect multiple ceramic capacitors in par-
allel to achieve the required bulk capacitance. To mini-
mize audible noise generated by the ceramic capacitors
during PWM dimming, it could be necessary to minimize
the number of ceramic capacitors on the output. In these
cases, an additional electrolytic or tantalum capacitor
provides most of the bulk capacitance.
The calculation of the output capacitance is the same for
both boost and buck-boost configurations. The output rip-
ple is caused by the ESR and the bulk capacitance of the
output capacitor if the ESL effect is considered negligible.
For simplicity, assume that the contributions from ESR and
the bulk capacitance are equal, allowing 50% of the ripple
for the bulk capacitance. The capacitance is given by:
SW
R4
is the switching frequency in hertz, V
R1
R1
=
C
IL
=
=
Boost and Buck-Boost Configurations
OUT
(V
P
(V
MAX
+
LED
2 L
2 L
LED
0.75D
×
×
≥
V
−
is the maximum duty cycle, IL
MIN
MIN
I
−
OUTRIPPLE
2V
LED
V
MAX
INMIN
0.418V
INMIN
×
×
× ×
f
f
SW
SW
2 D
V
) R4 1.5
LED
) R4 1.5
×
L
×
×
×
Output Capacitor
MIN SW
MAX
50 A
50 A
×
−
f
SW
µ
µ
V
×
×
f
INMIN
LED
is the LED
MIN
INMIN
is the
P