Datasheet
Evaluates: MAX8790A
MAX8790A Evaluation Kit
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Off-Board White LED String Configuration
The MAX8790A EV kit is also used to drive off-board
WLED strings. This allows the evaluation of up to 10
WLEDs per string. To evaluate external WLED strings,
remove the shunts from jumpers JU6–JU12. See Table
6 for jumpers JU6–JU11 and Table 7 for jumper JU12
configurations. Removing these jumpers effectively dis-
connects the on-board WLED strings from between the
output and feedback pins, allowing the connection of
external WLED strings. For each external WLED string,
connect the cathode terminal of the string to the corre-
sponding feedback pad (FB1–FB6), and connect the
anode terminal of the string to the VOUT pad. Once the
external WLED strings are connected between the
VOUT pad and the FB_ pins, the EV kit can be evaluat-
ed in the same manner as with the on-board WLED
strings. Evaluating more than eight WLEDs per string
could require component changes. Refer to the
MAX8790A IC data sheet for component selections.
Note: When evaluating more than eight WLEDs per
string, ensure that at low currents the forward voltage
drop across the strings is large enough to avoid
exceeding the 28V maximum rating of the FB pins [V
FB
= (V
OUT
- V
F_WLEDs
) < 28V].
LED String Capacitance
In some LCD panel applications, a 0.1µF (typ) capaci-
tor, C
LED
, is placed in parallel with each LED string to
improve ESD immunity. As such, the MAX8790A EV kit
provides a footprint across each LED string in addition
to footprints for pullup resistors on each FB_ pin. Refer
to the
LCD Panel Capacitance
section in the
MAX8790A IC data sheet for more detailed information.
SHUNT POSITION VOUT
Installed*
Connected to anodes of on-board
WLED strings
Not installed
Connect to anodes of off-board
WLED strings
Table 7. Jumper JU12 Function
*
Default position.
SHUNT
POSITION
FB_ PIN STRING_
1-2
Connected to cathode
of WLED string
Enabled
2-3 Connected to GND Disabled
Not installed
Connect to an external
WLED string
On-board WLED
string not used
Table 6. Jumpers JU6–JU11 Function