beautypg.com

Max6948b, I/o ports (p0–p4) – Rainbow Electronics MAX6948B User Manual

Page 14

background image

High-Efficiency PWM LED Driver with Boost

Converter and Five Constant-Current GPIO Ports

14

MAX6948B

I/O Ports (P0–P4)

The MAX6948B contains five I/O ports (P0–P4). Configure
the five I/O ports as logic inputs, open-drain logic outputs,
or constant-current sinks in any combination. Table 7
provides a detailed description of the individual port con-
figuration registers. Use registers 0x00 to 0x04 to individu-
ally assign each port (see the PWM Intensity Control and

Phasing section). Use registers 0x0A, 0x0B, and 0x0C to
assign the same port setting to multiple ports (Table 1).
When powered off, the I/O ports remain in high impedance.
Figure 1 shows the I/O port structure of the MAX6948B.
I/O ports P0–P4 default to high impedance on power-up,
to prevent connected ports from drawing current. Ports
used as inputs do not load their source signals.

Table 7. Port Registers Format (0x00 to 0x04, 0x0A, 0x0B, and 0x0C)

Figure 1. Simplified Schematic of I/O Ports

REGISTER DESCRIPTION

REGISTER DATA

D7

D6

D5

D4

D3

D2

D1

D0

Port is logic-low. Port is still active in shutdown mode.

0

0

0

0

0

0

0

0

Port is logic-high. Set this mode when using GPIO as an input.
Port is still active when in shutdown mode.

0

0

0

0

0

0

0

1

Port is a static constant-current sink. Port is high impedance
when in shutdown mode.

0

0

0

0

0

0

1

0

Port is a constant-current sink with a 3/256 duty cycle. Port is
high impedance when in shutdown mode.

0

0

0

0

0

0

1

1

Port is a constant-current sink with a 4/256 duty cycle. Port is
high impedance when in shutdown mode.

0

0

0

0

0

1

0

0

Port is a constant-current sink with a 5/256 duty cycle. Port is
high impedance when in shutdown mode.

0

0

0

0

0

1

0

1

U

U

U

Port is a constant-current sink with a 254/256 duty cycle. Port is
high impedance when in shutdown mode.

1

1

1

1

1

1

1

0

Power-up default setting (port is high impedance)

1

1

1

1

1

1

1

1

8-BIT LATCH

OUTPUT PORT

REGISTER

PWM

GENERATOR

1-BIT LATCH

OUTPUT-CURRENT

REGISTER

4-BIT DAC

3-BIT LATCH

GLOBAL-CURRENT

REGISTER

READ I/O

PORT COMMAND

TO/FROM

SERIAL

INTERFACE

MSB

ENABLE

A

B

n-CHANNEL
MOSFET

I/O PORT

ENABLE = 0x00

SET

CURRENT

POSITION A: 0x00 TO 0x01
POSITION B: 0x02 TO 0xFF

CLOSE SWITCH: 0x02 TO 0xFE