MAX16809_07 Datasheet, PDF (19/23 Pages) Maxim Integrated Products – Integrated 16-Channel LED Drivers with Switch-Mode Boost and SEPIC Controller

Integrated 16-Channel LED Drivers with
Switch-Mode Boost and SEPIC Controller
LED Dimming
PWM Dimming
All the output channels can be dimmed simultaneously
by applying a PWM signal (50Hz to 30kHz) to OE. This
allows for a wide range of dimming up to a 5000:1 ratio.
Each channel can be independently turned on and off
using a 4-wire serial interface. The dimming is propor-
tional to the PWM duty cycle.
LED Current Amplitude Adjustment
Using an analog or digital potentiometer as R_SET allows
for LED current amplitude adjustment and linear dimming.
Computing Power Dissipation
Use the following equation to estimate the upper limit
power dissipation (PD) for the MAX16809/MAX16810:
⎡
i = 15
⎤
PD = DUTY × _⎢(V + x I+) + ∑ V_OUTi x I_OUTi⎥
⎣⎢
i=0
⎦⎥
+ (V_CC x I_CC)
where:
V+ = supply voltage
I+ = V+ operating supply current
DUTY = PWM duty cycle applied to OE
V_OUTi = MAX16809/MAX16810 port output voltage
when driving load LED(s)
I_OUTi = LED drive current programmed by R_SET
PD = power dissipation
PCB Layout Guidelines
Careful PCB layout is critical to achieve low switching
losses and clean, stable operation. Use a multilayer
board whenever possible for better noise immunity.
Protect sensitive analog grounds by using a star
ground configuration. Minimize ground noise by con-
necting AGND, PGND, the input bypass-capacitor
ground lead, and the output-filter ground lead to a sin-
gle point (star ground configuration). Also, minimize
trace lengths to reduce stray capacitance, trace resis-
tance, and radiated noise. The trace between the out-
put voltage-divider and the FB pin must be kept short,
as well as the trace between AGND and PGND.
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