MAX7326 Maxim, MAX7326 Datasheet - Page 15

• Manufacturer Part Number: MAX7326
• Description: The MAX7326, a 2-wire serial-interfaced peripheral, features 12 push-pull outputs and four input ports with selectable internal pullups and transition detection
• Manufacturer: Maxim

The MAX7326’s SDA, SCL, AD0, AD2, RST, INT, and
I2–I5 are overvoltage protected to +6V independent of
V+. This allows the MAX7326 to operate from a lower
supply voltage, such as +3.3V, while the I
and/or any of the four input ports are driven from a
higher logic level, such as +5V.
The MAX7326 can operate from a higher supply volt-
age, such as +3V, while the I
of the four input ports I2–I5 are driven from a lower
logic level, such as +2.5V. For V+ < 1.8V, apply a mini-
mum voltage of 0.8 x V+ to assert a logic-high on any
input. For V+ ≥ 1.8V, apply a voltage of 0.7 x V+ to
assert a logic-high. For example, a MAX7326 operating
from a +5V supply may not recognize a +3.3V nominal
logic-high. One solution for input level translation is to
drive the MAX7326 inputs from open-drain outputs. Use
a pullup resistor to V+ or a higher supply to ensure a
high logic voltage of greater than 0.7 x V+.
Each of the push-pull output ports (O0, O1, and
O6–O15) has protection diodes to V+ and GND (Figure
11). When a port output is driven to a voltage higher
Figure 11. MAX7326 Push-Pull Output Port Structure
I
Port Output Signal Level Translation
OUTPUT
2
MAX7326
Port Input and I
C Port Expander with 12 Push-Pull Outputs
Translation from Higher or Lower
Applications Information
______________________________________________________________________________________
V+
2
V+
C interface and/or some
2
C Interface Level
Logic Voltages
O0, O1,
O6–O15
2
C interface
than V+ or below GND, the appropriate protection
diode clamps the output to a diode drop above V+ or
below GND. Do not overvolt output ports O0, O1, and
O6–O15. When the MAX7326 is powered down (V+ =
0), each output port appears as a diode clamp to GND
(Figure 11).
Each of the four input ports I2–I5 has a protection diode
to GND (Figure 12). When a port input is driven to a
voltage lower than GND, the protection diode clamps
the output to a diode drop below GND.
Each of the four input ports (I2–I5) also has a 40kΩ
(typ) pullup resistor that can be enabled or disabled.
When a port input is driven to a voltage higher than V+
the body diode of the pullup enable switch conducts
and the 40kΩ pullup resistor is enabled. When the
MAX7326 is powered down (V+ = 0), each input port
appears as a 40kΩ resistor in series with a diode con-
nected to zero. Input ports are protected to +6V under
any of these circumstances (Figure 12).
When driving LEDs from one of the 12 output ports (O0,
O1, or O6–O15), a resistor must be fitted in series with
the LED to limit the LED current to no more than 20mA.
Connect the LED cathode to the MAX7326 port, and
the LED anode to V+ through the series current-limiting
resistor, R
Figure 12. MAX7326 Input Port Structure
ENABLE
INPUT
PULLUP
LED
. Set the port output low to light the LED.
V+
V+
and 4 Inputs
40kΩ
MAX7326
Driving LED Loads
I2–I5
15
,