MAX6957AAX+T Maxim Integrated Products, MAX6957AAX+T Datasheet - Page 13

• 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

Table 3. Register Address Map (continued)
Note: Unused bits read as 0.
Display test mode turns on all ports configured as LED
drivers by overriding, but not altering, all controls and
port registers, except the port configuration register
(Table 14). Only ports configured as LED drivers are
affected. Ports configured as GPIO push-pull outputs
do not change state. In display test mode, each port's
current is temporarily set to 1/2 the maximum current
limit as controlled by R
The MAX6957 uses an external resistor R
maximum segment current. The recommended value,
39kΩ, sets the maximum current to 24mA, which makes
the segment current adjustable from 1.5mA to 24mA in
1.5mA steps.
To set a different segment current, use the formula:
where I
The recommended value of R
8 ports 16–23 (data bits D0–D7)
8 ports 17–24 (data bits D0–D7)
8 ports 18–25 (data bits D0–D7)
8 ports 19–26 (data bits D0–D7)
8 ports 20–27 (data bits D0–D7)
8 ports 21–28 (data bits D0–D7)
8 ports 22–29 (data bits D0–D7)
8 ports 23–30 (data bits D0–D7)
8 ports 24–31 (data bits D0–D7)
7 ports 25–31 (data bits D0–D6. D7 reads as 0)
6 ports 26–31 (data bits D0–D5. D6, D7 read as 0)
5 ports 27–31 (data bits D0–D4. D5–D7 read as 0)
4 ports 28–31 (data bits D0–D3. D4–D7 read as 0)
3 ports 29–31 (data bits D0–D2. D3–D7 read as 0)
2 ports 30–31 (data bits D0–D1. D2–D7 read as 0)
1 port 31 only (data bit D0. D1–D7 read as 0)
SEG
Selecting External Component R
28-Port LED Display Driver and I/O Expander
4-Wire-Interfaced, 2.5V to 5.5V, 20-Port and
is the desired maximum segment current in mA.
to Set Maximum Segment Current
R
______________________________________________________________________________________
ISET
REGISTER
Display Test Register
ISET
= 936kΩ / I
.
ISET
is 39kΩ.
SEG
ISET
to set the
ISET
R/ W
R/ W
R/ W
R/ W
D15
R/ W
R/ W
R/ W
R/ W
R/ W
R/ W
R/ W
R/ W
R/ W
R/ W
R/ W
R/ W
D14
The recommended value of R
allowed value, since it sets the display driver to the
maximum allowed segment current. R
higher value to set the segment current to a lower maxi-
mum value where desired. The user must also ensure
that the maximum current specifications of the LEDs
connected to the driver are not exceeded.
The drive current for each segment can be controlled
through programming either the global current register
(Table 9) or individual segment current registers
(Tables 10, 11, and 12), according to the setting of the
current control bit of the configuration register (Table 7).
These registers select the LED’s constant-current drive
from 16 equal fractions of the maximum segment cur-
rent. The current difference between successive cur-
rent steps, I
formula:
If I
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
SEG
D13
= 24mA, then I
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
COMMAND ADDRESS
D12
STEP
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
, is therefore determined by the
I
STEP
D11
STEP
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
= I
= 24mA / 16 = 1.5mA.
SEG
D10
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
/ 16
ISET
D9
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
is the minimum
ISET
D8
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
can be a
CODE
0x5A
0x5B
0x5C
0x5D
HEX
0x50
0x51
0x52
0x53
0x54
0x55
0x56
0x57
0x58
0x59
0x5E
0x5F
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