MAX8790EVKIT+ Maxim Integrated, MAX8790EVKIT+ Datasheet - Page 4

• Manufacturer Part Number: MAX8790EVKIT+
• Description: LED Lighting Development Tools
• Manufacturer: Maxim Integrated
• Series: MAX8790r

Specifications of MAX8790EVKIT+

• Rohs: yes
• Product: Evaluation Kits

MAX8790A Evaluation Kit
The MAX8790A provides a 100:1 dimming range
through analog or digital control methods. In both meth-
ods, the BRT input signal is translated into a control sig-
nal for each of the six current sources. By varying the
BRT duty cycle, the LED string current (I
ed between 0mA and the full-scale current setting. See
the Setting Full-Scale LED Current (I
details on configuring the full-scale current. To select
the dimming mode, configure jumper JU3 as shown in
Table 5, and see the Direct DPWM Dimming Mode and
Analog + DPWM Dimming Mode sections for additional
information.
To enable DPWM dimming, configure jumper JU3 as
listed in Table 5, and ensure that a shunt is installed
across jumper JU5.
In direct DPWM dimming mode, I
whose amplitude is equal to the full-scale current set-
ting. The duty cycle of the I
with the BRT signal, such that at 50% BRT duty cycle
the I
dimming mode, the internal phase-locked loop (PLL) is
not used and does not limit the BRT frequency. Refer to
the MAX8790A IC data sheet for information on deter-
mining the maximum allowable BRT frequency.
* Default position.
Table 5. Jumpers JU3, JU5 Function
* Default position.
4
Table 4. Jumper JU4 Function
Not installed*
JU3
2-3*
POSITION
1-2
_______________________________________________________________________________________
LED
Installed
SHUNT
duty cycle are also 50%. While in direct DPWM
Connected to GND
Connected to VCC
Connected to GND
through R1 and R2
Connected to VCC
ENA PIN
ISET PIN
Direct DPWM Dimming Mode
LED
LED Dimming Mode
signal is synchronized
LED
LED(FS)
Not installed (connected to GND through R3)
is a PWM signal
Adjustable from
15mA to 25mA
LED
I LED(FS)
20mA
) section for
) is adjust-
Installed (connected to VCC)
JU5 (FSET)
To enable analog + DPWM dimming, configure jumper
JU3 as listed in Table 5, and ensure that a shunt is not
installed across jumper JU5.
In analog dimming mode, I
amplitude is modulated by the duty cycle of the BRT
input signal. Therefore, at 50% BRT duty cycle, the I
DC signal is set to 50% of the full-scale current. While in
analog dimming mode, the BRT frequency is limited to
the capture range of the internal PLL. The free-running
frequency of the PLL is set by R3 to 244Hz, providing a
capture range of 147Hz to 244Hz. Refer to the
MAX8790A IC data sheet for information on configuring
the PLL’s free-running frequency.
This analog control scheme holds true down to a BRT
duty cycle of 12.5%. Below 12.5%, the string currents
are modulated through a combination of analog and
digital dimming schemes. Refer to the MAX8790A IC
data sheet for further details.
As configured, the MAX8790A EV kit is assembled with
two strings of eight WLEDs (String1 and String2), but
can be reconfigured to drive up to six strings of eight
WLEDs. Each string has an associated 3-pin header
(JU6–JU11) and feedback pin (FB1–FB6). To evaluate
additional strings (String3–String6), the EV kit must be
reconfigured as follows:
1) Populate the String_ with either the WLED listed in
2) Cut the trace (solder side) between pins 2-3 of the
3) Install a 3-pin header (JU8–JU11) and configure its
To evaluate the EV kit with off-board WLED strings, see
the Off-Board White LED String Configuration section.
the Component List or its equivalent.
string’s associated header-footprint (JU8–JU11).
shunt according to Table 6.
White LED String Configuration
Analog + DPWM Dimming Mode
LED
DIMMING MODE
Analog + DPWM
Direct DPWM
is a DC signal whose
LED