Rainbow Electronics MAX6964 - Manual (Page 16)

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.
Power-Supply Considerations
The MAX6964 operates with a power-supply voltage of
2V to 3.6V. Bypass the power supply to GND with at
least 0.047µF as close to the device as possible.
MAX6964
17-Output LED Driver/GPO
with Intensity Control
16 ______________________________________________________________________________________
Table 9. PWM Intensity Settings (Blink Disabled)
PWM DUTY CYCLE
OUTPUT BLINK PHASE 0
REGISTER BIT = 0
PWM DUTY CYCLE
OUTPUT BLINK PHASE 0
REGISTER = 1
OUTPUT
(OR
GLOBAL)
INTENSITY
SETTING
LOW TIME HIGH TIME
LED BEHAVIOR WHEN
OUTPUT BLINK PHASE 0
REGISTER BIT = 0
(LED IS ON WHEN
OUTPUT IS LOW)
LOW TIME HIGH TIME
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 Static low Static low
Full intensity, no PWM
(LED on continuously)
Static high
impedance
Static high
impedance
LED off continuously
Figure 19. Diode-Protected Switching Inductive Load
MAX6964
O8
O10
O0
O1
O2
O3
O4
O5
O6
O7
V+
2V TO 3.6V
µC
SDA
SCL
BLINK
SDA
I/O
AD0
O11
O12
O13
O14
O15
SCL
I/O
O9
GND
0.047µF
RST
MMTBT4148
5V