Detailed Description
The MAX1916 provides constant-current bias supply
for white LED designs. The MAX1916 uses a single
resistor to set the bias current for up to three LEDs.
LED bias currents are matched to 0.3% by the
MAX1916’s unique current-matching architecture
(Figure 1). Supply current (I
EN
) is a low 40µA in normal
operation and 0.05µA when disabled.
The MAX1916 offers several advantages over using
ballast resistors, such as improved LED-to-LED bright-
ness matching, lower bias variation with supply voltage
changes, significantly lower dropout voltage, and in
some applications, significantly improved efficiency.
The MAX1916 achieves a 200mV dropout with a 9mA
load on each output.
For circuits requiring only one or two LEDs, leave
unused LED outputs unconnected.
Enable Input
EN powers the input of the MAX1916. Drive EN high
(> 2.5V) to enable the device; drive EN low (< 2.2V) to
disable the device. When driven high, EN draws 40µA
to power the IC. Driving EN low forces LED1, LED2,
LED3, and SET into a high-impedance state.
MAX1916
Low-Dropout, Constant-Current
Triple White LED Bias Supply
_______________________________________________________________________________________ 5
Enable Input/Power Input. Drive high (> 2.5V) to enable; drive low (< 2.2V) to disable. When
disabled, SET, LED1, LED2, and LED3 are high impedance. When enabled, EN is the power input
for the MAX1916.
Bias Current Set Input. The current flowing into SET sets the bias current into each LED by
. V
is internally biased to 1.215V. SET is high impedance when EN is low.
LED 3 Cathode Connection. Current flowing into LED3 is 230 times the current flowing into SET.
LED3 is high impedance when EN is low.
LED 2 Cathode Connection. Current flowing into LED2 is 230 times the current flowing into SET.
LED2 is high impedance when EN is low.
LED 1 Cathode Connection. Current flowing into LED1 is 230 times the current flowing into SET.
LED1 is high impedance when EN is low.
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