MAX16802AEUA+ Maxim Integrated Products, MAX16802AEUA+ Datasheet - Page 8

• Manufacturer Part Number: MAX16802AEUA+
• Description: IC LED DRIVER HIGH BRIGHT 8-MSOP
• Manufacturer: Maxim Integrated Products
• Type: HBLED Driverr

Specifications of MAX16802AEUA+

• Constant Current: Yes
• Topology: Flyback, PWM, SEPIC, Step-Down (Buck), Step-Up (Boost)
• Number Of Outputs: 1
• Internal Driver: No
• Type - Primary: Backlight
• Type - Secondary: High Brightness LED (HBLED), RGB
• Frequency: 230kHz ~ 290kHz
• Voltage - Supply: 10.8 V ~ 24 V
• Mounting Type: Surface Mount
• Package / Case: 8-MSOP, Micro8™, 8-uMAX, 8-uSOP,
• Operating Temperature: -40°C ~ 85°C
• Current - Output / Channel: 3A
• Internal Switch(s): No
• Low Level Output Current: 500 uA (Min)
• High Level Output Current: 500 uA (Min)
• Operating Supply Voltage: 10.8 V to 24 V
• Maximum Supply Current: 1.4 mA
• Maximum Power Dissipation: 362 mW
• Maximum Operating Temperature: + 85 C
• Mounting Style: SMD/SMT
• Minimum Operating Temperature: - 40 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Voltage - Output: -
• Efficiency: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

in applications with higher input DC voltages by imple-
menting resistor-Zener bias (Figure 2a) or transistor-
Zener-resistor bias (Figure 2b).
The MAX16801/MAX16802 have an input voltage
UVLO/EN pin. The threshold of this UVLO is +1.28V.
Before any operation can commence, the voltage on
this pin has to exceed +1.28V. The UVLO circuit keeps
the CPWM comparator, ILIM comparator, oscillator,
and output driver in shutdown to reduce current con-
sumption (see the Functional Diagram). Use this UVLO
function to program the input start voltage. Calculate
the divider resistor values, R2 and R3 (Figure 5), by
using the following formulas:
The value of R3 is calculated to minimize the voltage-
drop error across R2 as a result of the input bias cur-
rent of the UVLO/EN pin. V
50nA (max), V
where the power supply must start.
where I
V
Offline and DC-DC PWM Controllers for
High-Brightness LED Drivers
Figure 2. (a) Resistor-Zener and (b) Transistor-Zener-Resistor Bias Arrangements
8
ULR2
_______________________________________________________________________________________
is the UVLO/EN wake-up threshold.
UVLO
MAX16801/MAX16802 Undervoltage
R
3
IN
is the UVLO/EN pin input current, and
≅
500
is the value of the input-supply voltage
R
VDC
2
=
×
V
V
IN
I
ULR
UVLO IN
V
R
D
−
ULR
2
V
ULR
(
ULR2
×
2
V
V
2
IN
(a)
−
V
= +1.28V, I
×
ULR
R
IN
3
2
)
MAX16802A
Lockout
UVLO
=
VDC
In addition to the externally programmable UVLO func-
tion offered in both the MAX16801/MAX16802, the
MAX16801 has an additional internal bootstrap UVLO
that is very useful when designing high-voltage LED
drivers (see the Functional Diagram). This allows the
device to bootstrap itself during initial power-up. The
MAX16801 attempts to start when V
bootstrap UVLO threshold of +23.6V. During startup,
the UVLO circuit keeps the CPWM comparator, ILIM
comparator, oscillator, and output driver shut down to
reduce current consumption. Once V
+23.6V, the UVLO circuit turns on both the CPWM and
ILIM comparators, as well as the oscillator, and allows
the output driver to switch. If V
the UVLO circuit will shut down the CPWM comparator,
ILIM comparator, oscillator, and output driver thereby
returning the MAX16801 to the startup mode.
In isolated LED driver applications, V
from a tertiary winding of a transformer. However, at
startup there is no energy delivered through the trans-
former. Therefore, a special bootstrap sequence is
required. Figure 3 shows the voltages on IN and V
during startup. Initially, both V
the line voltage is applied, C1 charges through the
startup resistor R1 to an intermediate voltage. At this
point, the internal regulator begins charging C2 (see
Figure 5). The MAX16801 uses only 45µA of the current
supplied by R1, and the remaining input current
charges C1 and C2. The charging of C2 stops when
the V
the voltage across C1 continues rising until it reaches
R
D
CC
Q
C
voltage reaches approximately +9.5V, while
MAX16801 Bootstrap Undervoltage
(b)
MAX16801 Startup Operation
IN
MAX16802A
IN
IN
and V
drops below +9.7V,
IN
CC
IN
can be derived
exceeds the
are 0V. After
IN
Lockout
reaches
CC