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MAX16822BEVKIT Dane(HTML) 3 Page - Maxim Integrated Products

Numer części MAX16822BEVKIT
Szczegółowy opis  MAX16822B Evaluation Kit
Pobierz  6 Pages
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Producent  MAXIM [Maxim Integrated Products]
Strona internetowa  http://www.maxim-ic.com
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MAX16822BEVKIT Datasheet(Arkusz danych) 3 Page - Maxim Integrated Products

   
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MAX16822B Evaluation Kit
_______________________________________________________________________________________
3
Enable and HBLED Dimming Control
The MAX16822B EV kit features a jumper to enable and
disable the MAX16822B IC (U1). Installing jumper JU1
disables the MAX16822B IC. Additionally, HBLED dim-
ming is achieved on the MAX16822B EV kit by applying
a digital PWM signal at the DIM PCB input pad.
Remove the shunt at jumper JU1 to enable HBLED dim-
ming using a digital PWM signal at the DIM and PGND
PCB pads. Apply a digital PWM signal with a 0.6V
logic-low (or less) and a 2.8V logic-high (or more) level
and frequencies from 200Hz to 20kHz. To adjust the
HBLED brightness, vary the signal duty cycle from 0 to
100%. See Table 1 for jumper JU1 setting of the HBLED
dimming operation.
Thermal Foldback and
Temperature Simulation
The MAX16822B EV kit features a thermal foldback and
temperature simulation circuit available at the TEMP_I
PCB pad and jumper JU2. Jumper JU2 sets the mode
of operation, temperature simulation, or thermal fold-
back. Potentiometer R2 and resistor R3 form the
adjustable temperature simulation circuit. Test points
TP1 and TP2 (PGND) provide access to the signal for
adjusting the voltage.
To evaluate the MAX16822B IC thermal foldback fea-
ture, remove jumper JU2 and connect an NTC thermis-
tor to the TEMP_I and PGND PCB pads. Refer to the
Thermal Foldback section in the MAX16822A/
MAX16822B IC data sheet for information on using the
thermal foldback feature. See Table 2 for configuring
jumper JU2 for the desired mode of operation.
Setting External HBLED Current
Resistor R1 sets the MAX16822B EV kit average
HBLED current up to 333mA. However, the HBLED
average current can be set up to 350mA after replacing
resistor R1. Use the following equation to calculate R1
when reconfiguring the HBLED current:
where ILED is the desired HBLED average current.
Refer to the
Selecting RSENSE to Set LED Current sec-
tion in the MAX16822A/MAX16822B IC data sheet for
information on setting the HBLED current.
R
V
ILED
1
02
=
.
Table 1. Enable and HBLED Dimming
(Jumper JU1)
SHUNT
POSITION
DIM PIN
EV KIT ENABLE OR
DIMMING OPERATION
Not
installed
Connected to VIN
through resistor R4
Enabled or analog
dimming*
(see Table 2)
Not
installed
Connected to PWM
signal
Enabled, PWM signal
applied at DIM PCB pad
Installed
Connected to PGND
Disabled
*
Analog dimming is achieved by placing a resistor (RDIM)
across the TEMP_I and PGND PCB pads. Remove the shunt
across jumpers JU1 and JU2 and use the following equation to
calculate the current for the TEMP_I PCB pad resistor, which is
necessary to reduce the HBLED driving current. Refer to the
Analog Dimming section in the MAX16822A/MAX16822B IC
data sheet for information on the analog dimming feature.
ILEDDIM = ILED [1 - 0.75 x (2 - (RDIM x 26.5µA))]
where RDIM is the TEMP_I pad resistor, ILEDDIM is the
required current for the desired HBLED current, and ILED is
configured for 322mA.
Alternatively, installing jumper JU2 and adjusting potentiometer
R2 can simulate analog dimming. Or, for DC control analog
dimming, install jumper JU2 and apply a DC voltage in the
0.7V to 2V range at the TP1 (positive) and TP2 (PGND) test
points.
Table 2. Temperature Simulation and
Thermal Foldback (Jumper JU2)
SHUNT
POSITION
TEMP_I PIN
EV KIT OPERATION
Installed
Connected to R2 and R3
Temperature simulation
Not
installed
Connected to external
NTC thermistor
Thermal foldback


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