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PDF MAX6954AAX Data sheet ( Hoja de datos )
| Número de pieza | MAX6954AAX | |
| Descripción | 2.7V to 5.5V LED Display Driver | |
| Fabricantes | Maxim Integrated | |
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MAX6954
4-Wire Interfaced, 2.7V to 5.5V LED Display
Driver with I/O Expander and Key Scan
General Description
The MAX6954 is a compact display driver that inter-
faces microprocessors to a mix of 7-segment, 14-seg-
ment, and 16-segment LED displays through an SPI-/
QSPI™-compatible 4-wire serial interface. The serial
interface may be cascaded through multiple devices.
The MAX6954 drives up to 16 digits 7-segment, 8 dig-
its 14-segment, 8 digits 16-segment, or 128 discrete
LEDs, while functioning from a supply voltage as low as
2.7V. The driver includes five I/O expander (or GPIO)
lines, some or all of which may be configured as
a key-switch reader, which automatically scans and
debounces a matrix of up to 32 switches.
Included on chip are full 14- and 16-segment ASCII
104-character fonts, a hexadecimal font for 7-segment
displays, multiplex scan circuitry, anode and cathode driv-
ers, and static RAM that stores each digit. The maximum
segment current for the display digits is set using a single
external resistor. Digit intensity can be independently
adjusted using the 16-step internal digital brightness con-
trol. The MAX6954 includes a low-power shutdown mode,
a scan-limit register that allows the user to display from 1
to 16 digits, segment blinking (synchronized across mul-
tiple drivers, if desired), and a test mode, which forces all
LEDs on. The LED drivers are slew-rate limited to reduce
EMI.
For a 2-wire interfaced version, refer to the MAX6955
data sheet. An evaluation kit (EV kit) for the MAX6955 is
available.
Applications
●● Set-Top Boxes
●● Panel Meters
●● White Goods
●● Bar Graph Displays
●● Audio/Video Equipment
Ordering Information
PART
TEMP RANGE
PIN-PACKAGE
MAX6954AAX
-40°C to +125°C
36 SSOP
MAX6954APL
-40°C to +125°C
40 PDIP
MAX6954ATL+
-40°C to +125°C
40 TQFN-EP*
+Denotes a lead-free/RoHS-compliant package.
*EP = Exposed pad.
QSPI is a trademark of Motorola, Inc.
MICROWIRE is a registered trademark of National
Semiconductor Corp.
Features
●● High-Speed 26MHz SPI/QSPI/MICROWIRE®-
Compatible Serial Interface
●● 2.7V to 5.5V Operation
●● Drives Up to 16 Digits 7-Segment, 8 Digits
14-Segment, 8 Digits 16-Segment, 128 Discrete
LEDs, or a Combination of Digit Types
●● Drives Common-Cathode Monocolor and Bicolor LED
Displays
●● Built-In ASCII 104-Character Font for 14-Segment
and 16-Segment Digits and Hexadecimal Font for
7-Segment Digits
●● Automatic Blinking Control for each Segment
●● 10µA (typ) Low-Power Shutdown (Data Retained)
●● 16-Step Digit-by-Digit Digital Brightness Control
●● Display Blanked on Power-Up
●● Slew-Rate Limited Segment Drivers for Lower EMI
●● Five GPIO Port Pins Can Be Configured as Key-
Switch Reader to Scan and Debounce Up to 32
Switches with n-Key Rollover
●● IRQ Output when a Key Input Is Debounced
●● 36-Pin SSOP and 40-Pin DIP and TQFN Packages
●● Automotive Temperature Range Standard
Functional Diagram
ISET
CURRENT
SOURCE
OSC
OSC_OUT
DIVIDER/
COUNTER
NETWORK
GPIO
AND KEY-SCAN
CONTROL
PWM
BRIGHTNESS
CONTROL
DIGIT
MULTIPLEXER
P0 TO P4
LED
DRIVERS
O0 TO O23
MAX6954
CHARACTER
GENERATOR
ROM
BLINK
BLINK
CONTROL
CONFIGURATION
RAM REGISTER
CLK
CS
DIN
DOUT
4-WIRE SERIAL INTERFACE
Pin Configurations and Typical Operating Circuits appear
at end of data sheet.
19-2460; Rev 5; 7/14
1 page  
MAX6954
4-Wire Interfaced, 2.7V to 5.5V LED Display
Driver with I/O Expander and Key Scan
Typical Operating Characteristics (continued)
(V+ = 3.3V, LED forward voltage = 2.4V, typical application circuit, TA = +25°C, unless otherwise noted.)
DEAD CLOCK OSCILLATOR FREQUENCY
vs. SUPPLY VOLTAGE
110
RSET = 56kΩ
105 OSC = GND
100
95
90
85
80
2.5
3.0 3.5 4.0 4.5 5.0
SUPPLY VOLTAGE (V)
5.5
WAVEFORM AT PINS O0 AND O18,
MAXIMUM INTENSITY
MAX6954 toc06
O0
0V
O18
0V
1V/div
200µs/div
PORT INPUT PULLUP CURRENT
vs. TEMPERATURE
0.30
OUTPUT = HIGH
VPORT = 1.4V
0.25 VCC = 5.5V
0.20
0.15
0.10
VCC = 3.3V
0.05
VCC = 2.5V
0
-40 -10 20
50
80
TEMPERATURE (°C)
110
SEGMENT SOURCE CURRENT
vs. SUPPLY VOLTAGE
1.02
1.00
0.98
0.96
0.94
0.92
2.5
VLED = 1.8V
3.0 3.5 4.0 4.5 5.0
SUPPLY VOLTAGE (V)
5.5
GPIO SINK CURRENT
vs. TEMPERATURE
45
40
OUTPUT = LOW
VPORT = 0.6V
35
30 VCC = 5.5V
25
20 VCC = 3.3V
15 VCC = 2.5V
10
5
0
-40
-10 20 50 80
TEMPERATURE (°C)
110
KEYSCAN OPERATION
(KEY_A AND IRQ)
MAX6954 toc09
KEY_A
0V
IRQ
0V
400µs/div
KEY_A: 1V/div
IRQ: 2V/div
www.maximintegrated.com
Maxim Integrated │ 5
5 Page 
MAX6954
4-Wire Interfaced, 2.7V to 5.5V LED Display
Driver with I/O Expander and Key Scan
A logic-high selects hexadecimal decoding, while a
logic-low bypasses the decoder. When direct control is
selected, the data bits D7 to D0 correspond to the seg-
ment lines of the MAX6954. Write x0010000 to blank all
segments in hexadecimal decode mode.
Display Blink Mode
The display blinking facility, when enabled, makes the
driver flip automatically between displaying the digit reg-
ister data in planes P0 and P1. If the digit register data
for any digit is different in the two planes, then that digit
appears to flip between two characters. To make a char-
acter appear to blink on or off, write the character to one
plane, and use the blank character (0x20) for the other
plane. Once blinking has been configured, it continues
automatically without further intervention.
Blink Speed
The blink speed is determined by the frequency of the
multiplex clock, OSC, and by the setting of the Blink Rate
Selection Bit B (Table 18) in the configuration register.
The Blink Rate Selection Bit B sets either fast or slow
blink speed for the whole display.
Initial Power-Up
On initial power-up, all control registers are reset, the
display is blanked, intensities are set to minimum, and
shutdown is enabled (Table 15).
Configuration Register
The configuration register is used to enter and exit shut-
down, select the blink rate, globally enable and disable
the blink function, globally clear the digit data, select
between global or digit-by-digit control of intensity, and
reset the blink timing (Tables 16–19 and 21–24).
The configuration register contains 7 bits:
●● S bit selects shutdown or normal operation (read/write).
●● B bit selects the blink rate (read/write).
●● E bit globally enables or disables the blink function
(read/write).
●● T bit resets the blink timing (data is not stored—tran-
sient bit).
●● R bit globally clears the digit data for both planes P0
and P1 for ALL digits (data is not stored—transient
bit).
●● I bit selects between global or digit-by-digit control
of intensity (read/write).
●● P bit returns the current phase of the blink timing
(read only—a write to this bit is ignored).
Character Generator Font Mapping
The font is composed of 104 characters in ROM. The
lower 7 bits of the 8-bit digit register represent the char-
acter selection. The most significant bit, shown as x in the
ROM map of Tables 7 and 8, is 1 to light the DP segment
and zero to leave the DP segment unlit.
The character map follows the standard ASCII font for
96 characters in the x0101000 through x1111111
range. The first 16 characters of the 16-segment ROM
map cover 7-segment displays. These 16 characters
are numeric 0 to 9 and characters A to F (i.e., the hexa-
decimal set).
Multiplex Clock and Blink Timing
The OSC pin can be fitted with capacitor CSET to GND
to use the internal RC multiplex oscillator, or driven by an
external clock to set the multiplex clock frequency and
blink rate. The multiplex clock frequency determines the
frequency that the complete display is updated. With OSC
at 4MHz, each display digit is enabled for 200µs.
The internal RC oscillator uses an external resistor, RSET,
and an external capacitor, CSET, to set the oscillator fre-
quency. The suggested values of RSET (56kΩ) and CSET
(22pF) set the oscillator at 4MHz, which makes the blink
frequency 0.5Hz or 1Hz.
The external clock is not required to have a 50:50 duty
cycle, but the minimum time between transitions must
be 50ns or greater and the maximum time between
transitions must be 750ns.
The on-chip oscillator may be accurate enough for appli-
cations using a single device. If an exact blink rate is
required, use an external clock ranging between 1MHz
and 8MHz to drive OSC. The OSC inputs of multiple
MAX6954s can be tied together to a common external
clock to make the devices blink at the same rate. The
relative blink phasing of multiple MAX6954s can be syn-
chronized by setting the T bit in the control register for all
the devices in quick succession. If the serial interfaces of
multiple MAX6954s are daisy-chained by connecting the
DOUT of one device to the DIN of the next, then synchro-
nization is achieved automatically by updating the config-
uration register for all devices simultaneously. Figure 6 is
the multiplex timing diagram.
OSC_OUT Output
The OSC_OUT output is a buffered copy of either the
internal oscillator clock or the clock driven into the OSC
pin if the external clock has been selected. The feature
is useful if the internal oscillator is used, and the user
wishes to synchronize other MAX6954s to the same
blink frequency. The oscillator is disabled while the
MAX6954 is in shutdown.
www.maximintegrated.com
Maxim Integrated │ 11
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| PDF Descargar | [ Datasheet MAX6954AAX.PDF ] | |
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