MAX16823EVKIT データシートの表示（PDF） - Maxim Integrated
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MAX16823EVKIT Datasheet PDF : 6 Pages
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MAX16823 Evaluation Kit
2) Connect a digital voltmeter across the IN and GND
pads and the other voltmeter across the LEDGOOD
and GND pads.
3) Verify that shunts are installed across pins 1-2 of
jumpers JU1, JU2, and JU3 (LEDs at full intensity).
4) Verify that a shunt is installed across pins 2-3 of
jumper JU4 (on-board LEDs selected at OUT3),
and that a shunt is not installed on jumper JU5
(LEDs current set to 50mA).
5) Verify that the shunts are installed on jumpers JU6
and JU7 (on-board LEDs selected at OUT1 and
OUT2).
6) Turn on the power supply and increase the input
voltage to 12V. The LEDs should illuminate with full
brightness.
7) Verify that the voltmeter at LEDGOOD measures
approximately 3.4V.
Detailed Description
The MAX16823 EV kit demonstrates the MAX16823 IC
LED driver. The MAX16823 outputs (OUT1, OUT2, and
OUT3) are configured to supply 50mA to the on-board
LEDs. The MAX16823 EV kit operates over the input-
voltage range of 6.5V to 16V and requires a 1A power
supply. The MAX16823 IC can operate from 5.5V to
40V. Refer to the MAX16823 data sheet for proper con-
figuration.
The MAX16823 EV kit outputs are current controlled by
monitoring the voltage across the respective output’s
external low-side sense resistors (R2, R3, and R4). The EV
kit features 3 series-connected LEDs at each channels’
output. All outputs provide pads to evaluate external
LEDs by bypassing the on-board LEDs after configur-
ing the appropriate jumpers. Two of the outputs can be
used to evaluate LEDs with current rated up to 70mA. A
third output (OUT_3) provides 550mA (typ) to the exter-
nal user-supplied LEDs using transistor Q1 and cur-
rent-sense resistor R5.
The MAX16823 EV kit features PC pads to control the
PWM dimming function of each output channel. The
MAX16823 EV kit also features a PCB pad to monitor
the status of the LEDGOOD output, which is pulled up
to REG by resistors R6 and R7.
Typically, capacitor C1 is not required if the power sup-
ply is relatively close to the EV kit. If long wires are
used to connect the power supply to the EV kit, sur-
face-mount 1206 PC pads are provided for adding
additional bulk capacitance at C1.
Output Current Setting
The output current for the on-board LEDs is set to
50mA (typ) with resistors R2, R3, or R4.
Use the following equation to adjust the respective
channel’s output current at OUT1, OUT2, OUT3, or
OUT_3:
R_
=
203mV(typ)
ILED
where R_ is the external current-sense resistor at CS1,
CS2, CS3, or CS_3, and ILED is the desired output cur-
rent in milliamperes.
The output current for the LEDs, with the exception of
external LEDs at OUT_3, can be adjusted to a maxi-
mum 70mA by replacing the respective resistor.
When a shunt is installed across pins 1-2 of jumper
JU4, and a shunt is installed at jumper JU5, the output
current for the external LEDs at OUT_3 is set to 550mA
(typ) by the parallel resistors combination R2 and R5,
connected at CS_3.
PWM Dimming
The MAX16823 EV kit features PWM input PCB pads
(DIM1, DIM2, and DIM3) that can be used to control
LED brightness at each output using external logic sig-
nals. Jumpers JU1, JU2, and JU3 control the on and off
condition of the EV kit LEDs. Install shunts across pins
1-2 to turn on the LEDs current. Install shunts across
pins 2-3 to turn off the LEDs’ current. See Table 1 for
PWM configuration.
Table 1. PWM Configuration (JU1, JU2,
and JU3)
SHUNT
POSITION
DIM1, DIM2, DIM3
PINS
EV KIT
FUNCTION
1-2
REG
LEDs on
2-3
GND
LEDs off
Not installed
Driven by external
source
PWM operation
To operate the MAX16823 EV kit in PWM operation,
remove the shunts at jumpers JU1, JU2, or JU3 for indi-
vidual PWM control of the respective channels.
Connect digital PWM signals at the DIM1, DIM2, and
DIM3 pads with a 2.8V to VIN logic level and square-
wave frequencies from DC to 3kHz. Vary the duty cycle
to adjust the LED brightness. LED brightness increases
when the duty cycle increases and vice versa. When
the PWM signal duty cycle at DIM_ is 100%, the LEDs
are fully on.
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