MAXIM MAX6950, MAX6951 User Manual
General Description
The MAX6950/MAX6951 are compact common-cathode
display drivers that interface microprocessors to individual 7-segment numeric LED digits, bar graph, or discrete
LEDs through an SPI™-, QSPI™-, MICROWIRE™-compatible serial interface. The supply voltage can be as low
as 2.7V.
The MAX6950 drives up to five 7-segment digits or 40
discrete LEDs. The MAX6951 drives up to eight 7-segment digits or 64 discrete LEDs.
Included on-chip are hexadecimal character decoders
(0–9, A–F), multiplex scan circuitry, segment and digit
drivers, and a static RAM that stores each digit. The
user may select hexadecimal decoding or no-decode
for each digit to allow any mix of 7-segment digits, bar
graph, or discrete LEDs to be driven. The segment current for the LEDs is set by an internal digital brightness
control. The segment drivers are slew-rate limited to
reduce EMI.
Individual digits may be addressed and updated without rewriting the entire display. The devices include a
low-power shutdown mode, digital brightness control, a
scan-limit register that allows the user to display from
one to eight digits, segment blinking that can be synchronized across drivers, and a test mode that forces
all LEDs on.
Applications
Set-Top Boxes
Panel Meters
White Goods
Bar Graphs and Matrix Displays
Industrial Controllers and Instrumentation
Professional Audio Equipment
Medical Equipment
Features
♦ High-speed 26MHz SPI-, QSPI-, MICROWIRE-
Compatible Serial Interface
♦ +2.7V to +5.5V Operation
♦ Individual LED Segment Control
♦ Segment Blinking Control that Can Be
Synchronized Across Multiple Drivers
♦ Hexadecimal Decode/No-Decode Digit Selection
♦ Digital Brightness Control
♦ Display Blanked on Power-Up
♦ Drives Common-Cathode LED Digits
♦ Multiplex Clock Syncronizable to External Clock
♦ Slew-Rate Limited Segment Drivers for Low EMI
♦ 75µA Low-Power Shutdown (Data Retained)
♦ Small 16-Pin QSOP Package
MAX6950/MAX6951
Serially Interfaced, +2.7V to +5.5V,
5- and 8-Digit LED Display Drivers
________________________________________________________________ Maxim Integrated Products 1
Pin Configuration
19-2227; Rev 2; 3/05
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
Ordering Information
Functional Diagram appears at end of data sheet.
Typical Application appears at end of data sheet.
SPI and QSPI are trademarks of Motorola, Inc.
MICROWIRE is a trademark of National Semiconductor Corp.
*EP = Exposed pad.
EVALUATION KIT
AVAILABLE
PART TEMP RANGE PIN-PACKAGE
MAX6950CEE 0°C to +70°C 16 QSOP-EP*
MAX6950EEE -40°C to +85°C 16 QSOP-EP*
MAX6951CEE 0°C to +70°C 16 QSOP-EP*
MAX6951EEE -40°C to +85°C 16 QSOP-EP*
TOP VIEW
1
DIN V+
CLK
2
DIG3/SEG3
DIG2/SEG2
DIG1/SEG1
DIG0/SEG0
ISET
GND
3
MAX6950
4
MAX6951
5
6
7
8
16
15
14
13
12
11
10
9
CS
DIG4/SEG4
(DIG5)/SEG5
(DIG6)/SEG6
(DIG7)/SEG7
SEG8
OSC
( ) MAX6951 ONLY
QSOP
MAX6950/MAX6951
Serially Interfaced, +2.7V to +5.5V,
5- and 8-Digit LED Display Drivers
2 _______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
Voltage (with Respect to GND)
V+………………………………. ...................................-0.3V to 6V
All Other Pins................................................-0.3V to (V+ + 0.3V)
DIG1–DIG8 Sink Current.................................................. 440mA
SEG1–SEG9 Source Current.............................................. 55mA
Continuous Power Dissipation (T
A
= +70°C)
16-Pin QSOP (derate 8.34mW/°C above +70°C)........667mW
Operating Temperature Ranges (T
MIN
to T
MAX
)
MAX695_CEE....................................................0°C to +70°C
MAX695_EEE.................................................-40°C to +85°C
Junction Temperature......................................................+150°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
ELECTRICAL CHARACTERISTICS
(Typical operating circuit, V+ = +3.0V to +5.5V, TA= T
MIN
to T
MAX
, unless otherwise noted.) (Note 1)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Operating Supply Voltage V+ 2.7 5.5 V
Shutdown Supply Current I
Operating Supply Current I+
Master Clock Frequency (OSC
Internal Oscillator)
Master Clock Frequency (OSC
External Clock)
Display Scan Rate (OSC
External Clock)
Display Scan Rate (OSC Internal
Oscillator)
Display Scan Rate (OSC Internal
Oscillator)
OSC Internal/External Detection
Threshold
Dead Clock Protection
Frequency
OSC High Time (OSC External
Clock)
OSC Low Time (OSC External
Clock)
SHDN
f
OSC
f
OSC
f
SCAN
f
SCAN
f
SCAN
V
OSC
f
OSC
t
CH
t
CL
S hutd ow n m od e, al l d i g i tal
i np uts at V + or GN D
All segments on, all digits scanned,
intensity set to full, internal oscillator,
no display load connected
OSC = RC oscillator 1 8
OSC = RC oscillator, R
= 27pF
C
SET
OSC overdriven externally 1 8 MHz
Eight digits scanned, OSC = overdriven
externally
Eight digits scanned, OSC = RC oscillator 155 1250 Hz
Eight digits scanned, OSC = RC oscillator,
R
= 56kΩ, C
SET
Overtemperature 75
T
= +25oC 62 160
A
= 56kΩ,
SET
= 27pF
SET
155 1250 Hz
50 ns
50 ns
10 15 mA
4
625 Hz
1.7 V
75.5 kHz
µA
MHz
MAX6950/MAX6951
Serially Interfaced, +2.7V to +5.5V,
5- and 8-Digit LED Display Drivers
_______________________________________________________________________________________ 3
ELECTRICAL CHARACTERISTICS
(Typical operating circuit, V+ = +3.0V to +5.5V, TA= T
MIN
to T
MAX
, unless otherwise noted.) (Note 1)
Note 1: All parameters tested at TA= +25°C. Specifications over temperature are guaranteed by design.
Note 2: Guaranteed by design.
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Slow Segment Blink Period
(Internal Oscillator)
Fast Segment Blink Period
(Internal Oscillator)
f
S LOWBLIN K
f
FASTBLIN K
Fast or Slow Segment Blink Duty
Cycle (Note 2)
Digit Drive Sink Current I
Segment Drive Source Current I
Digit Drive Sink Current (Note 2) I
Segment Drive Source Current
(Note 2)
Slew Rate Rise Time ∆I
DIGIT
SEG
DIGIT
I
SEG
SEG
LOGIC INPUTS
Input Current DIN, CLK, CS IIH, I
Logic High Input Voltage DIN,
CLK, CS
Logic Low Input Voltage DIN,
CLK, CS
V
IH
V
IL
H yster esi s V ol tag e D IN , C LK, C S ∆V
TIMING CHARACTERISTICS (Figure 1)
CLK Clock Period t
CLK Pulse Width High t
CLK Pulse Width Low t
C S Fall to CLK Ri se S etup Ti m et
CLK Ri se to CS Rise Hold Time t
DIN Setup Time t
DIN Hold Time t
CS Pulse High t
CP
CH
CL
CSS
CSH
DS
DH
CSW
TIMING CHARACTERISTICS (V+ = +2.7V) (Note 2)
CLK Clock Period t
CLK Pulse Width High t
CLK Pulse Width Low t
C S Fall to CLK Ri se Setup Time t
CLK Ri se to CS Rise Hold Time t
DIN Setup Time t
DIN Hold Time t
CS Pulse High t
CP
CH
CL
CSS
CSH
DS
DH
CSW
Eight digits scanned, OSC = RC oscillator,
R
Eight digits scanned, OSC = RC oscillator,
R
TA = +25°C, V
TA = +25°C, V
TA = +25°C, V+ = 2.7V to 3V, V
TA = +25°C, V+ = 2.7V to 3V, V
/∆tTA = +25°C 35 mA/µs
VIN = 0 or V+ -2 2 µA
IL
I
= 56kΩ, C
SET
= 56kΩ, C
SET
SET
SET
= 27pF
= 27pF
1s
0.5 s
49.9 50 50.1 %
= 2.4V 240 320 400 mA
LED
= 2.4V -30 -40 -50 mA
LED
= 2.2V 80 mA
LED
= 2.2V -10 mA
LED
2.4 V
0.5 V
38.4 ns
19 ns
19 ns
9.5 ns
3ns
9.5 ns
0ns
19 ns
50 ns
24 ns
24 ns
12 ns
4ns
12 ns
4ns
24 ns
0.4 V
MAX6950/MAX6951
Serially Interfaced, +2.7V to +5.5V,
5- and 8-Digit LED Display Drivers
4 _______________________________________________________________________________________
Typical Operating Characteristics
(Typical operating circuit, scan limit set to eight digits, V+ = +3.3V, V
LED
= 2.4V, TA = +25°C, unless otherwise noted.)
INTERNAL OSCILLATOR FREQUENCY
vs. TEMPERATURE
4.40
4.30
4.20
4.10
4.00
3.90
3.80
OSCILLATOR FREQUENCY (MHz)
3.70
3.60
-40 0 20-20
V+ = 2.7V
V+ = 3.3V
V+ = 5V
40
TEMPERATURE (°C)
INTERNAL OSCILLATOR WAVEFORM
AT OSC (PIN 9)
3.0
2.5
2.0
1.5
VOLTAGE AT OSC (V)
1.0
0.5
0
0 400200 600 800
TIMELINE (ns)
60 80
MAX6950/1 toc01
MAX6950/1 toc03
INTERNAL OSCILLATOR FREQUENCY
vs. SUPPLY VOLTAGE
4.40
4.30
4.20
4.10
4.00
3.90
3.80
OSCILLATOR FREQUENCY (MHz)
3.70
3.60
23456
SUPPLY VOLTAGE (V)
DEAD CLOCK OSCILLATOR FREQUENCY
vs. SUPPLY VOLTAGE
80
79
78
77
76
75
74
73
OSCILLATOR FREQUENCY (kHz)
72
71
70
2.0 3.0 3.52.5 4.0 4.5 5.0 5.5 6.0
SUPPLY VOLTAGE (V)
MAX6950/1 toc02
MAX6950/1 toc04
SEGMENT SOURCE CURRENT
vs. SUPPLY VOLTAGE
1.01
1.00
0.99
0.98
0.97
CURRENT NORMALIZED TO 40mA
0.96
0.95
2.0 3.02.5 3.5 4.0 4.5 5.0 5.5 6.0
SUPPLY VOLTAGE (V)
MAX6950/1 toc05
WAVEFORM AT SEGO/DIGO (PIN 6)
V+ = 3.3V, 8 DIGITS SCANNED, 8/16 INTENSITY
3.5
3.0
2.5
2.0
1.5
VOLTAGE (V)
1.0
0.5
0
DIGIT 0 MULTIPLEX TIMESLOT
0 500 1000 1500 2000
TIMELINE (ns)
MAX6950/1 toc06
Detailed Description
Differences Between
MAX6950 and MAX6951
The MAX6950 is a five-digit common-cathode display
driver. It drives five digits, with each digit comprising
eight LEDs with cathodes connected to a common
cathode. The display limit is therefore 40 LEDs or digit
segments.
The MAX6951 is an eight-digit common-cathode display driver. It drives eight digits, with each digit comprising eight LEDs. The only difference between the
MAX6950 and MAX6951 is that the MAX6950 is missing
three digit drivers. The MAX6950 can be configured to
scan eight digits, but if the last three digits are wired
up, they do not light.
The MAX6950/MAX6951 use a unique multiplexing
scheme to minimize the connections between the driver
and LED display. The scheme requires that the segment connections are different to each of the five
(MAX6950) or eight (MAX6951) digits (Table 1). This is
shown in the Typical Application Circuit, which uses
single-digit type displays. The MAX6950/MAX6951 are
not intended to drive multidigit display types, which
have the segments internally wired together, unless the
segments are wired with the common cathodes to follow Table 1. The MAX6950/MAX6951 can drive multidigit LED displays that have the segments individually
pinned for each digit because then the digits can be
connected together correctly externally, just as if individual digits were used.
Serial-Addressing Modes
The microprocessor interface on the MAX6950/
MAX6951 is a SPI-compatible 3-wire serial interface
using three input pins (Figure 1). This interface is used
to write configuration and display data to the MAX6950/
MAX6951. The serial interface data word length is 16
bits, which are labeled D15–D0 (Table 2). D15–D8 contain the command address, and D7–D0 contain the
data. The first bit received is D15, the most-significant
bit (MSB). The three input pins are:
• CLK is the serial clock input, and may idle low or
high at the start and end of a write sequence.
• CS is the MAX6950/MAX6951s’ chip-select input,
and must be low to clock data into the MAX6950/
MAX6951.
• DIN is the serial data input, and must be stable
when it is sampled on the rising edge of the clock.
MAX6950/MAX6951
Serially Interfaced, +2.7V to +5.5V,
5- and 8-Digit LED Display Drivers
_______________________________________________________________________________________ 5
Pin Description
PIN NAME FUNCTION
1 DIN Serial Data Input. Data is loaded into the internal 16–bit Shift register on CLK’s rising edge.
2 CLK
3–6, 10–14 DIGX, SEGX
7I
8 GND Ground
9 OSC
15 CS
16 V+ Positive Supply Voltage. Bypass to GND with a 0.1µF capacitor.
PAD E xposed p ad Exposed pad on package underside. Connect to GND.
SET
Serial-Clock Input. On CLK’s rising edge, data is shifted into the Internal Shift register. On CLK’s
falling edge, data is clocked out of DOUT. CLK input is active only while CS is low.
Digit X outputs sink current from the display common cathode when acting as digit drivers.
Segment X drivers source current to the display. Segment/digit drivers are high impedance when
turned off.
Current Setting. Connect to GND through a resistor (R
together with capacitor C
Multiplexer Clock Input. A capacitor (C
multiplex clock is used. Resistor R
together set the multiplex clock frequency. When the external clock is used, OSC should be driven
by a 1MHz to 8MHz clock.
Chip-Select Input. Serial data is loaded into the Shift register while CS is low. The last 16 bits of
serial data are latched on CS’s rising edge.
, also sets the multiplex clock frequency.
SET
) is connected to GND when the internal RC oscillator
SET
(also used to set the peak current) and capacitor C
SET
) to set the peak current. This resistor,
SET
SET
MAX6950/MAX6951
The serial interface comprises a 16-bit shift register into
which DIN data is clocked on the rising edge of CLK
when CS is low. When CS is high, transitions on CLK do
not clock data into the shift register. When CS goes
high, the 16 bits in the shift register are parallel loaded
into a 16-bit latch. The 16 bits in the latch are then
decoded to determine and execute the command.
The MAX6950/MAX6951 are written to using the following sequence (Figure 2):
1) Take CLK low.
2) Take CS low. This enables the internal 16-bit shift
register.
3) Clock 16 bits of data in order, D15 first to D0 last,
into DIN, observing the setup and hold times.
4) Take CS high.
CLK and DIN may well be used to transmit data to other
peripherals. The MAX6950/MAX6951 ignore all activity
on CLK and DIN except when CS is low. Data cannot
be read from the MAX6950/MAX6951.
If fewer or greater than 16 bits are clocked into the
MAX6950/MAX6951 between taking CS low and taking
CS high again, the MAX6950/MAX6951 store the last 16
bits received, including the previous transmission(s).
The general case is when n bits (where n > 16) are
transmitted to the MAX6950/MAX6951. The last bits
comprising bits {n-15} to {n} are retained and are parallel loaded into the 16-bit latch as bits D15 to D0,
respectively (Figure 3).
Digit and Control Registers
Table 3 lists the addressable Digit and Configuration
registers. The digit registers are implemented by two
planes of 8-byte dual-port SRAM, P0 and P1.
Initial Power-Up
On initial power-up, all control registers are reset, the
display is blanked, and the MAX6950/MAX6951 enter
shutdown mode. Program the display driver prior to display use. Otherwise, it is initially set to scan five digits, it
does not decode data in the data registers, and the
Intensity register is set to its minimum value. Table 4
lists the register status after power-up.
Configuration Register
The configuration register is used to enter and exit shutdown, select the blink rate, globally enable and disable
the blink function, globally clear the digit data, and
reset the blink timing. Bit position D1 should always be
written with a zero when the configuration register is
updated. See Table 5 for configuration register format.
The S bit selects shutdown or normal operation.
The B bit selects the blink rate.
The E bit globally enables or disables the blink function.
The T bit resets the blink timing.
The R bit globally clears the digit data for both planes
P0 and P1 for all digits.
When the MAX6950/MAX6951 are in shutdown mode
(Table 6), the scan oscillator is halted; all segment and
digit drivers are high impedance. Data in the digit and
Serially Interfaced, +2.7V to +5.5V,
5- and 8-Digit LED Display Drivers
6 _______________________________________________________________________________________
Table 1. Standard Driver Connection to Single-Digit Displays
Table 2. Serial-Data Format (16 Bits)
DIG/SEG0
PIN 6
LED Digit 0 CC0 SEG dp SEG g SEG f SEG e SEG d SEG c SEG b SEG a
LED Digit 1 SEG dp CC1 SEG g SEG f SEG e SEG d SEG c SEG b SEG a
LED Digit 2 SEG dp SEG g CC2 SEG f SEG e SEG d SEG c SEG b SEG a
LED Digit 3 SEG dp SEG g SEG f CC3 SEG e SEG d SEG c SEG b SEG a
LED Digit 4 SEG dp SEG g SEG f SEG e CC4 SEG d SEG c SEG b SEG a
LED Digit 5 SEG dp SEG g SEG f SEG e SEG d CC5 SEG c SEG b SEG a
LED Digit 6 SEG dp SEG g SEG f SEG e SEG d SEG c CC6 SEG b SEG a
LED Digit 7 SEG dp SEG g SEG f SEG e SEG d SEG c SEG b CC7 SEG a
D15 D14 D13 D12 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0
DIG/SEG1
PIN 5
ADDRESS MSB DATA LSB
DIG/SEG2
PIN 4
DIG/SEG3
PIN 3
DIG/SEG4
PIN 14
DIG/SEG5
PIN 13
DIG/SEG6
PIN 12
DIG/SEG7
PIN 11
SEG 8
PIN 10
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