MAX6955AAX Maxim Integrated Products, MAX6955AAX Datasheet - Page 16

• Manufacturer Part Number: MAX6955AAX
• Description: LED Drivers Integrated Circuits (ICs)
• Manufacturer: Maxim Integrated Products

Specifications of MAX6955AAX

• Number Of Digits: 16
• Number Of Segments: 128
• Low Level Output Current: 935000 uA
• High Level Output Current: 55000 uA
• Operating Supply Voltage: 2.7 V to 5.5 V
• Maximum Supply Current: 30000 uA
• Maximum Power Dissipation: 941 mW
• Maximum Operating Temperature: + 125 C
• Mounting Style: SMD/SMT
• Package / Case: SSOP-36
• Minimum Operating Temperature: - 40 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

2-Wire Interfaced, 2.7V to 5.5V LED Display
Driver with I/O Expander and Key Scan
Each key press is scanned twice in a 25.6ms time peri-
od with a nominal oscillator frequency of 4MHz, as
shown in Figure 12. In the first key test period of 1.6ms,
input level at ports P0–P3 (Key_A, Key_B, Key_C, and
Key_D) are examined in conjunction with the signal-low
period of ports O0–O7 to see if any key is pressed. If
pressed, the corresponding key pressed register bit is
set. In the second key test period of 1.6ms, input level
at ports P0–P3 are examined again (debounce) to see if
the key is still pressed. If still pressed, the correspond-
ing debounce register bit is set. The debounce time
between key tests is 12.8ms.
Figure 7. Command Byte Received
Figure 8. Command and Single Data Byte Received
Figure 9. n Data Bytes Received
16
S
S
______________________________________________________________________________________
S
HOW CONTROL BYTE AND DATA BYTE MAP INTO
HOW CONTROL BYTE AND DATA BYTE MAP INTO
SLAVE ADDRESS
SLAVE ADDRESS
COMMAND BYTE IS STORED ON RECEIPT OF STOP CONDITION
ACKNOWLEDGE FROM MAX6955
ACKNOWLEDGE FROM MAX6955
SLAVE ADDRESS
MAX6955's REGISTERS
MAX6955's REGISTERS
R/W
R/W
0
ACKNOWLEDGE FROM MAX6955
0
A
A
D15
D15
R/W
D14
D14
D13
D13
0
ACKNOWLEDGE FROM MAX6955
COMMAND BYTE
ACKNOWLEDGE FROM MAX6955
COMMAND BYTE
D12
D12
A
D11
D11
D15
D10
D10
The port configuration register selects how the five port
pins are used. The port configuration register format is
described in Table 33.
The Key_A Mask, Key_B Mask, Key_C Mask, and
Key_D Mask write-only registers (Table 34) configure
the key-scanning circuit to cause an interrupt only when
selected (masked) keys have been debounced. Each
bit in the register corresponds to one key switch. The bit
is clear to disable interrupt for the switch, and set to
enable interrupt. Keys are always scanned (if enabled
through the port configuration register), regardless of
the setting of these interrupt bits, and the key status is
stored in the appropriate Key_x pressed register.
D9
D9
D14
D8
D8
D13
COMMAND BYTE
A
A
D12
D7
D7
ACKNOWLEDGE FROM MAX6955
D6
D6
Port Configuration Register
D11
D5
D5
AUTOINCREMENT MEMORY WORD ADDRESS
D10
AUTOINCREMENT MEMORY WORD ADDRESS
ACKNOWLEDGE FROM MAX6955
ACKNOWLEDGE FROM MAX6955
D4
D4
1 BYTE
DATA BYTE
n BYTE
DATA BYTE
D3
D3
D 9
Key Mask Registers
D2
D2
D 8
D1
D1
A
D0
D0
A
A
P
P
P