For example, to operate a 2.2V red LED at 14mA from a
5V supply, R
LED
= (5 - 2.2 - 0.25) / 0.014 = 182Ω.
Driving Load Currents Higher than 50mA
The MAX6964 can be used to drive loads drawing
more than 50mA, like relays and high-current white
LEDs, by paralleling outputs. Use at least one output
per 50mA of load current; for example, a 6V 330mW
relay draws 55mA and needs two paralleled outputs to
drive it. Ensure that the paralleled outputs chosen are
controlled by the same blink phase register, i.e., select
outputs from the O0 through O7 range, or the O8
through O15 range. This way, the paralleled outputs
are turned on and off together. Do not use output O16
as part of a load-sharing design. O16 cannot be
switched at the same time as any of the other outputs
because it is controlled by a different register.
The MAX6964 must be protected from the negative
voltage transient generated when switching off induc-
tive loads, such as relays, by connecting a reverse-
biased diode across the inductive load (Figure 19). The
peak current through the diode is the inductive load’s
operating current.
MAX6964
17-Output LED Driver/GPO with
Intensity Control and Hot-Insertion Protection
16 ______________________________________________________________________________________
Table 9. PWM Intensity Settings (Blink Disabled)
LED BEHAVIOR WHEN
OUTPUT BLINK PHASE 0
REGISTER BIT = 1
(LED IS ON WHEN
OUTPUT IS LOW)
0x0 1/16 15/16 Lowest PWM intensity 15/16 1/16 Highest PWM intensity
0x1 2/16 14/16 14/16 2/16
0x2 3/16 13/16 13/16 3/16
0x3 4/16 12/16 12/16 4/16
0x4 5/16 11/16 11/16 5/16
0x5 6/16 10/16 10/16 6/16
0x6 7/16 9/16 9/16 7/16
0x7 8/16 8/16 8/16 8/16
0x8 9/16 7/16 7/16 9/16
0x9 10/16 6/16 6/16 10/16
0xA 11/16 5/16 5/16 11/16
0xB 12/16 4/16 4/16 12/16
0xC 13/16 3/16 3/16 13/16
0xD 14/16 2/16
Increasing PWM intensity
2/16 14/16
Increasing PWM intensity
0xE 15/16 1/16 Highest PWM intensity 1/16 15/16 Lowest PWM intensity
0xF
