AN874 Datasheet, PDF (4/6 Pages) Maxim Integrated Products – Using the MAX6950 and the MAX6951 LED Display Drivers with Multiplex Dual-Digit Displays

LED
Digit
1
Discrete
LED anode
(cathode to
CC0)
LED
Digit
2
SEG f
LED
Digit
3
SEG f
LED
Digit
4
SEG d
LED
Digit
5*
SEG d
LED
Digit
6*
SEG b
LED
Digit
7*
SEG b
CC1
SEG g
SEG g
SEG g
SEG g
SEG g
SEG g
SEG g
SEG f
SEG e
SEG d
SEG c
SEG b
SEG
a
CC2
Discrete
LED anode
(cathode to
CC3)
SEG e
SEG d
SEG c
SEG b
SEG
a
Discrete
LED anode
(cathode to
CC2)
CC3
SEG e
SEG d
SEG c
SEG b
SEG
a
SEG f
SEG e
CC4
Discrete
LED anode
(cathode to
CC5)
SEG c
SEG b
SEG
a
SEG f
SEG e
Discrete
LED anode
(cathode to
CC4)
CC5
SEG c
SEG b
SEG
a
SEG f
SEG e
SEG d
SEG c
CC6
Discrete
LED anode SEG
(cathode to a
CC7 )
SEG f
SEG e
SEG d
SEG c
Discrete
LED anode
(cathode to
CC6)
CC7
SEG
a
*These digits are not available for the MAX6950.
The second solution can be used if all digits' segments are required. This time, hexadecimal-decode
operation can be selected because the standard segment connection pattern is used (Table 4). The
penalty for this configuration is that one diode is required per digit (Figure 2). Each diode is passing
only one segment's current, so it can be a low-cost single signal diode like 1N4148, BAS16 (silicon), or
BAT54, BAR43 (Schottky). Better still, use surface mount dual common-cathode diodes like BAV70
(silicon) and BAT54C (Schottky). The minimum supply voltage to the MAX6950/MAX6951 must also be
raised by the selected diode's forward voltage drop: typically 1.0V for a silicon signal diode or 0.4V for
a Schottky signal diode at 50mA.