Driving LED Loads

When driving LEDs from one of the four output ports

(O0, O1, O6, or O7), a resistor must be connected in

series with the LED to limit the LED current to no more

than 20mA. Connect the LED cathode to the MAX7321

port, and the LED anode to V+ through the series cur-

illuminate the LED. Choose the resistor value according

to the following formula:

where:

LED (

Ω).

For example, to operate a 2.2V red LED at 10mA from a

+5V supply:

Ω.

and 4 Open-Drain I/Os

______________________________________________________________________________________

13

OUTPUT

V+

V+

PORTS

O0, O1, O6, O7

MAX7323

Figure 9. MAX7323 Push-Pull Output Port Structure

PORTS

P2–P5

PULLUP

ENABLE

INPUT

OUTPUT

40k

Ω

G

S

D

MAX7323

V+

V+

Figure 10. MAX7323 I/O Port Structure

CONTROL

O7

P4

P5

O6

P3

P2

O1

O0

INT

I/O

PORTS

POWER-

ON RESET

INPUT

FILTER

RST

SDA

SCL

AD2

AD0

MAX7323

Functional Diagram