Maxim Integrated MAX16840 Evaluation Kit MAX16840EVKIT# MAX16840EVKIT# Ficha De Dados
Códigos do produto
MAX16840EVKIT#
_________________________________________________________________ Maxim Integrated Products 3
MAX16840 Evaluation Kit
Evaluates: MAX16840
Detailed Description of Hardware
The MAX16840 EV kit demonstrates the MAX16840
HBLED driver IC. The IC is an average current-mode-
control HBLED driver IC for step-down (buck), step-up
(boost), and step-down/step-up (buck-boost) topologies
in low-voltage SSL applications. The IC has an inte-
grated 0.2I (max), 48V switching MOSFET that allows
the device to be used in lighting applications for MR16
and other SSL applications for power levels up to 10W.
The IC uses a proprietary input current-control scheme
to achieve power-factor correction. The IC’s LED driver
uses constant-frequency average current-mode control
to control the duty cycle of the integrated switching
MOSFET. The IC is available in a 10-pin TDFN package
with an exposed pad.
The EV kit circuit is configured in a buck-boost topol-
ogy, which operates at the IC’s fixed 300kHz switching
frequency and provides up to 5.5W of output power for
a string of 3 to 5 series HBLEDs connected at the LED+
and LED- test-point holes. The EV kit circuit operates
from a 9V to 13.2V AC or DC supply voltage and from
electronic transformers. The EV kit is designed on a
proven 2oz copper, two-layer, small PCB-footprint design
that accommodates an MR16 application form factor.
The IC uses average current-mode control and the cir-
cuit is configured such that the average current flows in
current-sense resistor R3 on a cycle-by-cycle (switching
frequency) basis and is set by the voltage on the REFI
pin. The average current per switching cycle flowing into
R3 is:
HBLED driver IC. The IC is an average current-mode-
control HBLED driver IC for step-down (buck), step-up
(boost), and step-down/step-up (buck-boost) topologies
in low-voltage SSL applications. The IC has an inte-
grated 0.2I (max), 48V switching MOSFET that allows
the device to be used in lighting applications for MR16
and other SSL applications for power levels up to 10W.
The IC uses a proprietary input current-control scheme
to achieve power-factor correction. The IC’s LED driver
uses constant-frequency average current-mode control
to control the duty cycle of the integrated switching
MOSFET. The IC is available in a 10-pin TDFN package
with an exposed pad.
The EV kit circuit is configured in a buck-boost topol-
ogy, which operates at the IC’s fixed 300kHz switching
frequency and provides up to 5.5W of output power for
a string of 3 to 5 series HBLEDs connected at the LED+
and LED- test-point holes. The EV kit circuit operates
from a 9V to 13.2V AC or DC supply voltage and from
electronic transformers. The EV kit is designed on a
proven 2oz copper, two-layer, small PCB-footprint design
that accommodates an MR16 application form factor.
The IC uses average current-mode control and the cir-
cuit is configured such that the average current flows in
current-sense resistor R3 on a cycle-by-cycle (switching
frequency) basis and is set by the voltage on the REFI
pin. The average current per switching cycle flowing into
R3 is:
REFI
AV
V
I
6.075 R3
=
×
where V
REFI
is the voltage at the IC’s REFI pin and R3 is
in ohms.
Circuit components C3, C7, Q2, R4, and R7–R10 are
used to average the rectified AC voltage and control the
input current. Components R7 and C7 form a lowpass
filter, with the average input voltage present across C7.
Circuit components C3, C7, Q2, R4, and R7–R10 are
used to average the rectified AC voltage and control the
input current. Components R7 and C7 form a lowpass
filter, with the average input voltage present across C7.
The averaged voltage is then used to control the current
in the current-mirror circuit formed by R8, R9, R10, and
Q2. The current flowing into R8 is approximately propor-
tional to the voltage on C7 and is reflected on pin 3 of Q2
and sinks the same amount of current from pin 3 of Q2,
which flows into R8. The IC has a 50FA current source
available at the REFI pin. The current flowing into R4 sets
the input current or the average current flowing into R3.
The circuit attempts to maintain the input power over the
input voltage range of 9V AC to 13.2V AC almost con-
stant, thus achieving LED current regulation in the range
of Q10% over the input range.
Inductor L2 is 3.3FH and has no effect for DC input volt-
ages and low-frequency AC input voltages when the
MR16 is powered from a magnetic transformer. Figure
1 illustrates the input-current waveforms when the EV kit
is powered from a magnetic transformer with a 12V AC
60Hz output.
Inductor L2 has an effect when the unit is powered from
an electronic transformer (Figure 2).
Notice that the peak current drawn has increased with
the addition of the inductor (Figure 3). The first peak
drawn every 120Hz is ignored and consists of the input
current drawn by the IC circuit and the input capacitors.
in the current-mirror circuit formed by R8, R9, R10, and
Q2. The current flowing into R8 is approximately propor-
tional to the voltage on C7 and is reflected on pin 3 of Q2
and sinks the same amount of current from pin 3 of Q2,
which flows into R8. The IC has a 50FA current source
available at the REFI pin. The current flowing into R4 sets
the input current or the average current flowing into R3.
The circuit attempts to maintain the input power over the
input voltage range of 9V AC to 13.2V AC almost con-
stant, thus achieving LED current regulation in the range
of Q10% over the input range.
Inductor L2 is 3.3FH and has no effect for DC input volt-
ages and low-frequency AC input voltages when the
MR16 is powered from a magnetic transformer. Figure
1 illustrates the input-current waveforms when the EV kit
is powered from a magnetic transformer with a 12V AC
60Hz output.
Inductor L2 has an effect when the unit is powered from
an electronic transformer (Figure 2).
Notice that the peak current drawn has increased with
the addition of the inductor (Figure 3). The first peak
drawn every 120Hz is ignored and consists of the input
current drawn by the IC circuit and the input capacitors.
Maximum LED+ Voltage
The IC features an internal 46V overvoltage protection at
the IN pin to protect the internal switching MOSFET from
damage if the LED string is open or if the voltage on the
LED string is too high. However, when operating the EV
kit buck-boost circuit, the LED+ voltage should be limited
to 40V.
the IN pin to protect the internal switching MOSFET from
damage if the LED string is open or if the voltage on the
LED string is too high. However, when operating the EV
kit buck-boost circuit, the LED+ voltage should be limited
to 40V.
Electronic and Magnetic
Transformer Compatibility
The MR16 board was tested with 4 LEDs for electronic
and magnetic transformer compatibility and also with the
appropriate dimmers. See
and magnetic transformer compatibility and also with the
appropriate dimmers. See
Table 1 for the results with the
different transformer models tested.