rescent display (VFD) tube driver that interfaces a
multiplexed VFD tube to a VFD controller such as the
MAX6850–MAX6853 or to a microcontroller. The
MAX6920 is also ideal for driving either static VFD tubes
or telecom relays.
Data is inputted using an industry-standard 4-wire serial
interface (CLOCK, DATA, LOAD, BLANK) for compatibil-
ity with both industry-standard drivers and Maxim’s VFD
controllers.
For easy display control, the active-high BLANK input
forces all driver outputs low, turning the display off, and
automatically puts the MAX6920 into shutdown mode.
Display intensity may also be controlled by pulse-width
modulating the BLANK input.
The MAX6920 has a serial interface data output pin,
DOUT, allowing any number of devices to be cascaded
on the same serial interface.
The MAX6920 is available in a 20-pin SO pack-
age. Maxim also offers VFD drivers with either 20
(MAX6921/MAX6931) or 32 outputs (MAX6922 and
MAX6932).
Features
●
5MHz Industry-Standard 4-Wire Serial Interface
●
3V to 5.5V Logic Supply Range
●
8V to 76V Grid/Anode Supply Range
●
Push-Pull CMOS High-Voltage Outputs
●
Outputs can Source 40mA, Sink 4mA Continuously
●
Outputs can Source 75mA Repetitive Pulses
●
Outputs can be Paralleled for Higher Current Drive
●
Any Output can be Used as a Grid or an Anode
Driver
●
Blank Input Simplifies PWM Intensity Control
●
Small 20-Pin SO Package
●
-40°C to +125°C Temperature Range
●
White Goods
●
Gaming Machines
●
Avionics
Applications
●
Industrial Weighing
●
Security
●
Telecom
Ordering Information
PART
MAX6920AWP
TEMP RANGE
-40°C to +125°C
PIN-PACKAGE
20 Wide SO
Pin Configuration
TOP VIEW
V
BB
1
DOUT 2
OUT11 3
OUT10 4
OUT9 5
OUT8 6
OUT7 7
OUT6 8
BLANK 9
GND 10
20 V
CC
19 DIN
18 OUT0
17 OUT1
Typical Operating Circuit
+5V
C1
100nF
20
V
CC
µC
VFDOUT
VFCLK
VFLOAD
VFBLANK
19
11
12
9
DIN
CLK
LOAD
BLANK
GND
10
1
V
BB
12
+60V
C2
100nF
15 OUT3
14 OUT4
13 OUT5
12 LOAD
11 CLK
19-3061; Rev 1; 8/14
VFD TUBE
MAX6920AWP
16 OUT2
MAX6920
OUT0 – OUT11
MAX6920
12-Output, 76V, Serial-Interfaced VFD Tube Driver
Absolute Maximum Ratings
Voltage (with respect to GND)
V
BB
....................................................................-0.3V to +80V
V
CC
......................................................................-0.3V to +6V
OUT_ .....................................................-0.3V to (V
BB
+ 0.3V)
All Other Pins ....................................... -0.3V to (V
CC
+ 0.3V)
OUT_ Continuous Source Current ...................................-45mA
OUT_ Pulsed (1ms max, 1/4 max duty) Source Current ....-80mA
Total OUT_ Continuous Source Current ........................-540mA
Total OUT_ Continuous Sink Current ................................60mA
Total OUT_ Pulsed (1ms max, 1/4 max duty)
Source Current ...........................................................-960mA
OUT_ Sink Current .............................................................15mA
CLK, DIN, LOAD, BLANK, DOUT Current ......................±10mA
Continuous Power Dissipation
20-Pin Wide SO (derate 10mW/°C over T
A
= +70°C) ....800mW
Operating Temperature Range (T
MIN
to T
MAX
) -40°C to +125°C
Junction Temperature ......................................................+150°C
Storage Temperature Range ............................ -65°C to +150°C
Lead Temperature (soldering, 10s) ................................. +300°C
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.
Electrical Characteristics
(Typical Operating Circuit, V
BB
= 8V to 76V, V
CC
= 3V to 5.5V, T
A
= T
MIN
to T
MAX
, unless otherwise noted.) (Note 1)
PARAMETER
Logic Supply Voltage
Tube Supply Voltage
SYMBOL
V
CC
V
BB
All outputs OUT_
low, CLK = idle
All outputs OUT_
high, CLK = idle
All outputs OUT
_
low
Tube Supply Operating Current
CONDITIONS
MIN
3
8
TYP
MAX
5.5
76
UNITS
V
V
T
A
= +25°C
T
A
= -40°C to +125°C
T
A
= +25°C
T
A
= -40°C to +125°C
T
A
= +25°C
T
A
= -40°C to +125°C
T
A
= +25°C
T
A
= -40°C to +125°C
T
A
= +25°C
T
A
= -40°C to +85°C
T
A
= -40°C to +125°C
T
A
= -40°C to +85°C
T
A
= -40°C to +125°C
T
A
= +25°C
T
A
= -40°C to +85°C
T
A
= -40°C to +125°C
T
A
= +25°C
T
A
= -40°C to +85°C
T
A
= -40°C to +125°C
T
A
= +25°C
T
A
= -40°C to +85°C
T
A
= -40°C to +125°C
V
BB
- 2
V
BB
- 2.5
V
BB
- 3.5
V
BB
- 4.0
72
350
1
0.53
V
BB
- 1.1
170
200
650
700
2
4.2
0.85
0.9
mA
Logic Supply Operating Current
I
CC
µA
I
BB
All outputs OUT_
high
V
BB
≥ 15V,
I
OUT
= -25mA
High-Voltage OUT_
V
H
V
BB
≥ 15V,
I
OUT
= -40mA
8V < V
BB
< 15V,
I
OUT
= -25mA
V
BB
≥ 15V,
I
OUT
= 1mA
V
V
BB
- 1.2
V
BB
- 2.5
V
BB
- 3.0
0.75
1
1.5
1.9
0.8
1.1
1.6
2.0
V
Low-Voltage OUT_
V
L
8V < V
BB
< 15V,
I
OUT
= 1mA
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Maxim Integrated
│
2
MAX6920
12-Output, 76V, Serial-Interfaced VFD Tube Driver
Electrical Characteristics (continued)
(Typical Operating Circuit, V
BB
= 8V to 76V, V
CC
= 3V to 5.5V, T
A
= T
MIN
to T
MAX
, unless otherwise noted.) (Note 1)
PARAMETER
Rise Time OUT_ (20% to 80%)
Fall Time OUT_ (80% to 20%)
LOAD Rising to OUT_ Falling
Delay
LOAD Rising to OUT_ Rising Delay
BLANK Rising to OUT_ Falling
Delay
BLANK Falling to OUT_ Rising
Delay
Input Leakage Current
CLK, DIN, LOAD, BLANK
Logic-High Input Voltage
CLK, DIN, LOAD, BLANK
Logic-Low Input Voltage
CLK, DIN, LOAD, BLANK
Hysteresis Voltage
DIN, CLK, LOAD, BLANK
High-Voltage DOUT
Low-Voltage DOUT
Rise and Fall Time DOUT
CLK Clock Period
CLK Pulse-Width High
CLK Pulse-Width Low
CLK Rise to LOAD Rise Hold Time
DIN Setup Time
DIN Hold Time
DOUT Propagation Delay
LOAD Pulse High
t
CP
t
CH
t
CL
t
CSH
t
DS
t
DH
t
DO
t
CSW
3V to 4.5V
4.5V to 5.5V
C
DOUT
= 10pF
3.0V to 4.5V
4.5V to 5.5V
(Note 2)
I
IH
, I
IL
V
IH
V
IL
DV
I
V
OH
V
OL
I
SOURCE
= -1.0mA
I
SINK
= 1.0mA
C
DOUT
= 10pF
(Note 2)
3V to 4.5V
4.5V to 5.5V
200
90
90
100
5
20
15
25
20
55
120
75
240
150
60
30
V
CC
–
0.5
0.5
100
80
0.6
0.8 x
V
CC
0.3 x
V
CC
SYMBOL
t
R
t
F
CONDITIONS
V
BB
= 60V, C
L
= 50pF, R
L
= 2.3kW
V
BB
= 60V, C
L
= 50pF, R
L
= 2.3kW
MIN
TYP
0.9
0.6
MAX
2
1.5
UNITS
µs
µs
SERIAL INTERFACE TIMING CHARACTERISTICS
(Notes 2, 3)
(Notes 2, 3)
(Notes 2, 3)
(Notes 2, 3)
0.9
1.2
0.9
1.3
0.05
1.8
2.4
1.8
2.5
10
µs
µs
µs
µs
µA
V
V
V
V
V
ns
ns
ns
ns
ns
ns
ns
ns
ns
Note 1:
All parameters are tested at T
A
= +25°C. Specifications over temperature are guaranteed by design.
Note 2:
Guaranteed by design.
Note 3:
Delay measured from control edge to when output OUT_ changes by 1V.
www.maximintegrated.com
Maxim Integrated
│
3
MAX6920
12-Output, 76V, Serial-Interfaced VFD Tube Driver
Typical Operating Characteristics
(V
CC
= 5.0V, V
BB
= 76V, and T
A
= +25°C, unless otherwise noted.)
MAX6920 toc01
MAX6920 toc02
1.8
SUPPLY CURRENT (mA)
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
-40
-15
10
35
60
85
110
V
BB
= 40V
V
BB
= 8V
V
BB
= 76V
1.8
SUPPLY CURRENT (mA)
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
-40
-20
V
BB
= 40V
0
20
40
60
V
BB
= 8V
80
V
BB
= 76V
350
SUPPLY CURRENT (µA)
300
250
200
150
100
50
0
-40
V
CC
= 5V, CLK = 5MHz
V
CC
= 3.3V, CLK = 5MHz
V
CC
= 5V, CLK = IDLE
V
CC
= 3.3V, CLK = IDLE
-20
0
20
40
60
80
100 120
100 120
TEMPERATURE (°C)
TEMPERATURE (°C)
TEMPERATURE (°C)
550
SUPPLY CURRENT (A)
500
450
400
350
300
250
-40
V
CC
= 5V, CLK = 5MHz
MAX6920 toc04
3.0
OUTPUT VOLTAGE (V)
2.5
2.0
1.5
1.0
0.5
I
OUT
= -40mA
V
BB
= 8V
V
CC
= 3.3V, CLK = 5MHz
V
BB
= 40V
V
BB
= 76V
V
CC
= 5V, CLK = IDLE
V
CC
= 3.3V, CLK = IDLE
10
60
110
0
-40
-20
0
20
40
60
80
100 120
TEMPERATURE (°C)
TEMPERATURE (°C)
12
OUTPUT VOLTAGE (V)
10
8
6
4
2
0
-40
I
OUT
= 4mA
V
BB
= 76V
V
BB
= 40V
MAX6920 toc06
14
OUTPUT VOLTAGE
vs. TEMPERATURE (OUTPUT LOW)
OUTPUT RISE AND
FALL WAVEFORM
MAX6920 toc11
V
BB
= 8V
-20
0
20
40
60
80
100 120
1µs/div
TEMPERATURE (°C)
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Maxim Integrated
│
4
MAX6920 toc05
600
SUPPLY CURRENT (I
CC
)
vs. TEMPERATURE (OUTPUTS HIGH)
3.5
OUTPUT VOLTAGE (V
BB
- V
H
)
vs. TEMPERATURE (OUTPUT HIGH)
BLANK
2V/div
OUT_
20V/div
MAX6920 toc03
2.0
TUBE SUPPLY CURRENT (I
BB
)
vs. TEMPERATURE (OUTPUTS LOW)
2.0
TUBE SUPPLY CURRENT (I
BB
)
vs. TEMPERATURE (OUTPUTS HIGH)
400
LOGIC SUPPLY CURRENT (I
CC
)
vs. TEMPERATURE (OUTPUTS LOW)
MAX6920
12-Output, 76V, Serial-Interfaced VFD Tube Driver
Pin Description
PIN
1
2
3–8, 13–18
9
10
11
12
19
20
NAME
V
BB
DOUT
OUT0 to
OUT11
BLANK
GND
CLK
LOAD
DIN
V
CC
VFD Tube Supply Voltage
Serial-Clock Output. Data is clocked out of the internal shift register to DOUT on CLK’s rising edge.
VFD Anode and Grid Drivers. OUT0 to OUT11 are push-pull outputs swinging from V
BB
to GND.
Blanking Input. High forces outputs OUT0 to OUT11 low, without altering the contents of the output
latches. Low enables outputs OUT0 to OUT11 to follow the state of the output latches.
Ground
Serial-Clock Input. Data is loaded into the internal shift register on CLK’s rising edge.
Load Input. Data is loaded transparently from the internal shift register to the output latch while LOAD
is high. Data is latched into the output latch on LOAD’s rising edge, and retained while LOAD is low.
Serial-Data Input. Data is loaded into the internal shift register on CLK’s rising edge.
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