MAX6955 Maxim, MAX6955 Datasheet - Page 6

• Manufacturer Part Number: MAX6955
• Description: 2-Wire Interfaced / 2.7V to 5.5V LED Display Driver with I/O Expander and Key Scan
• Manufacturer: Maxim

The MAX6955 is a serially interfaced display driver that
can drive up to 16 digits 7-segment, 8 digits 14-seg-
ment, 8 digits 16-segment, 128 discrete LEDs, or a
combination of these display types. Table 1 shows the
drive capability of the MAX6955 for monocolor and
bicolor displays.
The MAX6955 includes 104-character ASCII font maps
for 14-segment and 16-segment displays, as well as
the hexadecimal font map for 7-segment displays. The
characters follow the standard ASCII font, with the addi-
tion of the following common symbols: £,
↑, and ↓. Seven bits represent the 104-character font
map; an 8th bit is used to select whether the decimal
point (DP) is lit. Seven-segment LED digits can be con-
trolled directly or use the hexadecimal font. Direct seg-
2-Wire Interfaced, 2.7V to 5.5V LED Display
Driver with I/O Expander and Key Scan
6
34, 35, 36
22–31
16, 18
19, 21
SSOP
7–15,
1, 2,
_______________________________________________________________________________________
17
20
32
33
—
3
4
5
6
PIN
38, 39, 40
17, 18, 20
21, 23, 24
16, 25
26–35
7–15,
PDIP
1, 2,
19
22
36
37
3
4
5
6
Detailed Description
OSC_OUT
O0–O18
NAME
P0–P4
BLINK
GND
ISET
OSC
AD0
SDA
AD1
N.C.
SCL
V+
General-Purpose I/O Ports (GPIOs). GPIO can be configured as logic inputs or open-drain
outputs. Enabling key scanning configures some or all ports P0–P3 as key-switch matrix
inputs with internal pullup and port P4 as IRQ output.
Address Input 0. Sets device slave address. Connect to GND, V+, SCL, or SDA to give four
logic combinations. See Table 5.
I
I
Address Input 1. Sets device slave address. Connect to GND, V+, SCL, or SDA to give four
logic combinations. See Table 5.
Digit/Segment Drivers. When acting as digit drivers, outputs O0 to O7 sink current from the
display common cathodes. When acting as segment drivers, O0 to O18 source current to the
display anodes. O0 to O18 are high impedance when not being used as digit or segment
drivers.
Ground
Segment Current Setting. Connect ISET to GND through series resistor R
current.
Positive Supply Voltage. Bypass V+ to GND with a 47µF bulk capacitor and a 0.1µF ceramic
capacitor.
Multiplex Clock Input. To use internal oscillator, connect capacitor C
To use external clock, drive OSC with a 1MHz to 8MHz CMOS clock.
Blink Clock Output. Output is open drain.
Clock Output. OSC_OUT is a buffered clock output to allow easy blink synchronization of
multiple MAX6955s. Output is push-pull.
Not Internally Connected
2
2
C-Compatible Serial Data I/O
C-Compatible Serial Clock Input
, ¥, °, µ, ±,
ment control allows the MAX6955 to be used to drive
bar graphs and discrete LED indicators.
Tables 2, 3, and 4 list the connection schemes for 16-,
14-, and 7-segment digits, respectively. The letters in
Tables 2, 3, and 4 correspond to the segment labels
shown in Figure 1. (For applications that require mixed
display types, see Tables 38–41.)
The MAX6955 operates as a slave that sends and
receives data through an I
face. The interface uses a serial data line (SDA) and a
serial clock line (SCL) to achieve bidirectional commu-
nication between master(s) and slave(s). A master (typ-
ically a microcontroller) initiates all data transfers to and
FUNCTION
2
C-compatible 2-wire inter-
Pin Description
SET
Serial Interface
from OSC to GND.
SET
Serial Addressing
to set the peak