General Description
The MAX7347/MAX7348/MAX7349 I2C interfaced periph-
erals provide microprocessors with management of up to
64 key switches. Key inputs are monitored statically, not
dynamically scanned, to ensure low-EMI operation. The
MAX7347 can monitor up to 24 switches, the MAX7348
can monitor up to 40 switches, and the MAX7349 can
monitor up to 64 switches. The switches can be metallic
or resistive (carbon) up to 5k
.
The key controller debounces and maintains a FIFO of
key-press events (including autorepeat, if enabled). An
interrupt (INT) output can be configured to alert key
presses either as they occur, or at maximum rate.
The MAX7348/MAX7349 feature a tone generator to
generate automatic key-click sounds or alarm tones
under processor control.
The sounder frequencies cover the 5th musical octave
(523.25Hz to 987.77Hz), plus seven other musical
notes up to 2637Hz. The output can also be pro-
grammed to be high or low for the sound duration to
operate an electronic sounder, relay, or lamp.
The MAX7347/MAX7348 are offered in 16-pin QSOP
and 20-pin QSOP packages, respectively. The
MAX7349 is available in 24-pin QSOP and 24-pin SO
packages. The MAX7347/MAX7348/MAX7349 operate
over the -40°C to +125°C temperature range.
Applications
Medical Instruments
Instrumentation Panels
Security and Access
Industrial Controls
Features
400kbps, 5.5V Tolerant 2-Wire Serial Interface
2.4V to 3.6V Operation
Monitor Up to 64 Keys (MAX7349AEG,
MAX7349WG), 40 Keys (MAX7348AEP), or 24
Keys (MAX7347AEE)
FIFO Queues Up to 8 Debounced Key Events
Key Debounce Time User Configurable from 9ms
to 40ms
Key Autorepeat Rate and Delay User Configurable
Low-EMI Design Uses Static Matrix Monitoring
Hardware Interrupt on Each Debounced Event or
FIFO Level, or at End of Definable Time Period
Up to Six Open-Drain Logic Outputs Available
Capable of Driving LEDs
Sounder Output Generates Automatic Key Clicks
14 Programmable Musical Sounder Frequencies
Continuous or Programmable Sounder Duration
Easy Automatic Single-Tone and Dual-Tone Alarm
Sound Generation
Four I2C Address Choices
Selectable 2-Wire Serial Bus Timeout
Under 10A Shutdown Current
MAX7347/MAX7348/MAX7349
2-Wire Interfaced Low-EMI Key Switch and
Sounder Controllers
________________________________________________________________ Maxim Integrated Products
1
Ordering Information
19-3556; Rev 1; 3/05
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
PART
TEMP RANGE
PIN-PACKAGE
MAX7347AEE
-40
°C to +125°C
16 QSOP
MAX7348AEP
-40
°C to +125°C
20 QSOP
MAX7349AEG
-40
°C to +125°C
24 QSOP
MAX7349AWG
-40
°C to +125°C
24 SO Wide
Purchase of I2C components from Maxim Integrated Products,
Inc., or one of its sublicensed Associated Companies, conveys a
license under the Philips I2C Patent Rights to use these compo-
nents in an I2C system, provided that the system conforms to the
I2C Standard Specification as defined by Philips.
MAX7349
V+
COL_
SOUNDER
GND
8
SCL
SDA
AD0
ALERT
ROW_
8
PIEZO
TRANSDUCER
SWITCH
ARRAY, UP
TO 64
SWITCHES
INPUT
2.4V TO 3.6V
INT
Typical Application Circuit
Pin Configurations appear at end of data sheet.