MAX6957AAX+T Maxim Integrated Products, MAX6957AAX+T Datasheet - Page 18

• Manufacturer Part Number: MAX6957AAX+T
• Description: IC DRVR DSPL LED 36-SSOP
• Manufacturer: Maxim Integrated Products

Specifications of MAX6957AAX+T

• Display Type: LED
• Configuration: 7, 16, 20 Segment
• Interface: 4-Wire Serial
• Current - Supply: 180µA
• Voltage - Supply: 2.5 V ~ 5.5 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 36-SSOP
• Number Of Segments: 28
• Low Level Output Current: 18 mA
• Operating Supply Voltage: 2.5 V to 5.5 V
• Maximum Supply Current: 230 uA
• Maximum Power Dissipation: 941 mW
• Maximum Operating Temperature: + 125 C
• Mounting Style: SMD/SMT
• Minimum Operating Temperature: - 40 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Digits Or Characters: -
• Lead Free Status / Rohs Status: Details

4-Wire-Interfaced, 2.5V to 5.5V, 20-Port and
28-Port LED Display Driver and I/O Expander
Bicolor digits group a red and a green die together for
each display element, so that the element can be lit
red, green (or orange), depending on which die (or
both) is lit. The MAX6957 allows each segment's cur-
rent to be set individually from 1/16th (minimum current
and LED intensity) to 16/16th (maximum current and
LED intensity), as well as off (zero current). Thus, a
bicolor (red-green) segment pair can be set to 289
color/intensity combinations. A discrete or CA tricolor
(red-green-yellow or red-green-blue) segment triad can
be set to 4913 color/intensity combinations.
Each MAX6957 port can sink a current of 24mA into an
LED with a 2.4V forward-voltage drop when operated
from a supply voltage of at least 3.0V. The minimum
voltage drop across the internal LED drivers is therefore
(3.0V - 2.4V) = 0.6V. The MAX6957 can sink 28 x 24mA
= 672mA when all outputs are operating as LED seg-
ment drivers at full current. On a 3.3V supply, a
MAX6957 dissipates (3.3V - 2.4V)
when driving 28 of these 2.4V forward-voltage drop
LEDs at full current. This dissipation is within the ratings
18
Table 11. Even Individual Segment Current Format
LED DRIVE
FRACTION
______________________________________________________________________________________
10/16
11/16
12/16
13/16
14/16
15/16
16/16
1/16
2/16
3/16
4/16
5/16
6/16
7/16
8/16
9/16
Driving Bicolor and Tricolor LEDs
Applications Information
R
CURRENT WITH
ISET
CONSTANT
SEGMENT
= 39kΩ (mA)
Power Dissipation Issues
10.5
13.5
16.5
19.5
22.5
1.5
4.5
7.5
12
15
18
21
24
3
6
9
✕
CODE (HEX)
672mA = 0.6W
0x12 to 0x1F
0x12 to 0x1F
0x12 to 0x1F
0x12 to 0x1F
0x12 to 0x1F
0x12 to 0x1F
0x12 to 0x1F
0x12 to 0x1F
0x12 to 0x1F
0x12 to 0x1F
0x12 to 0x1F
0x12 to 0x1F
0x12 to 0x1F
0x12 to 0x1F
0x12 to 0x1F
0x12 to 0x1F
ADDRESS
D7
See Table 12.
of the 36-pin SSOP package with an ambient tempera-
ture up to +98°C. If a higher supply voltage is used or
the LEDs used have a lower forward-voltage drop than
2.4V, the MAX6957 absorbs a higher voltage, and the
MAX6957's power dissipation increases.
If the application requires high drive current and high
supply voltage, consider adding a series resistor to
each LED to drop excessive drive voltage off-chip. For
example, consider the requirement that the MAX6957
must drive LEDs with a 2.0V to 2.4V specified forward-
voltage drop, from an input supply range is 5V ±5%
with a maximum LED current of 20mA. Minimum input
supply voltage is 4.75V. Maximum LED series resistor
value is (4.75V - 2.4V - 0.6V)/0.020A = 87.5Ω. We
choose 82Ω ±2%. Worst-case resistor dissipation is at
maximum toleranced resistance, i.e., (0.020A)
✕
per LED is at maximum input supply voltage, minimum
toleranced resistance, minimum toleranced LED for-
ward-voltage drop, i.e., 0.020 x (5.25V - 2.0V - (0.020A
✕
pation is 920mW, driving all 28 LEDs at 20mA full cur-
rent at once, which meets the 941mW dissipation
ratings of the 36-pin SSOP package.
D6
1.02) = 34mW. The maximum MAX6957 dissipation
82Ω x 0.98)) = 32.86mW. Worst-case MAX6957 dissi-
D5
D4
D3
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
D2
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
D1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
D0
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
HEX CODE
0xXA
0xXB
0xXC
0xXD
0xX0
0xX1
0xX2
0xX3
0xX4
0xX5
0xX6
0xX7
0xX8
0xX9
0xXE
0xXF
2
✕
(82Ω