MAX6931 [MAXIM]
20-Output, 76V, Serial-Interfaced VFD Tube Drivers;
| 型号： | MAX6931 |
| 厂家： | 
MAXIM INTEGRATED PRODUCTS |
| 描述： | 20-Output, 76V, Serial-Interfaced VFD Tube Drivers |
| 文件： | 总14页 (文件大小：275K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
19-3020; Rev 0; 10/03
20-Output, 76V, Serial-Interfaced
VFD Tube Drivers
General Description
Features
ꢀ 5MHz Industry-Standard 4-Wire Serial Interface
ꢀ 3V to 5.5V Logic Supply Range
The MAX6921/MAX6931 are 20-output, 76V, vacuum-
fluorescent display (VFD) tube drivers that interface a
multiplexed VFD tube to a VFD controller, such as the
MAX6850–MAX6853, or to a microcontroller. The
MAX6921/MAX6931 are also ideal for driving static VFD
tubes or telecom relays.
ꢀ 8V to 76V Grid/Anode Supply Range
ꢀ -11V to 0V Filament Bias Supply (MAX6931 Only)
ꢀ Push-Pull CMOS High-Voltage Outputs
Data is input using an industry standard 4-wire serial
interface (CLOCK, DATA, LOAD, BLANK), compatibile
with either Maxim’s or industry-standard VFD driver and
controller.
ꢀ Outputs can Source 40mA, Sink 4mA
Continuously
ꢀ Outputs can Source 75mA Repetitive Pulses
ꢀ Outputs can be Paralleled for Higher Current Drive
For easy display control, the active-high BLANK input
forces all driver outputs low, turning the display off, and
automatically puts the MAX6921/MAX6931 into shut-
down mode. Display intensity may also be controlled by
directly pulse-width modulating the BLANK input.
ꢀ Any Output can be Used as a Grid or an Anode
Driver
ꢀ Blank Input Simplifies PWM Intensity Control
ꢀ Small 28-Pin TSSOP Package
The MAX6921 has a serial interface data output, DOUT,
allowing any number of devices to be cascaded on the
same serial interface.
ꢀ -40°C to +125°C Temperature Range
The MAX6931 has a negative supply voltage input, V
allowing the drivers’ output swing to be made bipolar to
simplify filament biasing in many applications.
,
SS
Ordering Information
PART
MAX6921AUI
MAX6921AWI
MAX6921AQI
MAX6931AUI
TEMP RANGE
-40°C to +125°C
-40°C to +125°C
-40°C to +125°C
-40°C to +125°C
PIN-PACKAGE
28 TSSOP
The MAX6921 is available in 28-pin TSSOP, SO, and
PLCC packages. The MAX6931 is available in a 28-pin
TSSOP package.
28 Wide SO
28 PLCC
Maxim also offers 12-output VFD drivers (MAX6920) and
32-output VFD drivers (MAX6922/MAX6932).
28 TSSOP
Typical Operating Circuit
Applications
White Goods
Gaming Machines
Automotive
Industrial Weighing
Security
+5V
+60V
C2
100nF
C1
100nF
Telecom
Avionics
VFD Modules
Industrial Control
7
V
8
V
Instrumentation
CC
BB
µC
MAX6931
6
22
23
20
20
VFDOUT
VFCLK
DIN
OUT0–OUT19
CLK
VFLOAD
LOAD
BLANK
VFBLANK
V
GND
21
SS
9
-7V
C3
100nF
Pin Configurations appear at end of data sheet.
________________________________________________________________ Maxim Integrated Products
1
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.
20-Output, 76V, Serial-Interfaced
VFD Tube Drivers
ABSOLUTE MAXIMUM RATINGS
Voltage (with respect to GND)
OUT_ Sink Current .............................................................15mA
V
V
V
V
.........................................................................-0.3V to +80V
...........................................................................-0.3V to +6V
(MAX6931 only)...............................................-12V to +0.3V
CLK, DIN, LOAD, BLANK, DOUT Current ....................... 10mA
BB
CC
SS
BB
Continuous Power Dissipation (T = +70°C)
A
28-Pin TSSOP (derate 12.8mW/°C
over +70°C)................................................................1025mW
28-Pin Wide SO (derate 12.5mW/°C
over +70°C)................................................................1000mW
28-Pin PLCC (derate 10.5mW/°C
- V (MAX6931 only) .....................................-0.3V to +80V
SS
OUT_ (MAX6921 only) ..................(GND - -0.3V) to (V + 0.3V)
BB
BB
CC
OUT_ (MAX6931 only) ....................(V - -0.3V) to (V + 0.3V)
SS
All Other Pins..............................................-0.3V to (V
+ 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 .................................90mA
Total OUT_ Pulsed (1ms max, 1/4 max duty)
over +70°C)..................................................................842mW
Operating Temperature Range
(T
to T
) ...............................................-40°C to +125°C
MIN
MAX
Junction Temperature......................................................+150°C
Storage Temperature Range.............................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
Source Current ...........................................................-960mA
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 = 8V to 76V, V
= 3V to 5.5V, V = -11V to 0V, V - V ≤ 76V, T = T
to T
, unless other-
MAX
BB
CC
SS
BB
SS
A
MIN
wise noted.) (Note 1)
PARAMETER
Logic Supply Voltage
Tube Supply Voltage
SYMBOL
CONDITIONS
MIN
TYP
MAX
5.5
UNITS
V
CC
V
BB
3
8
V
V
76
Bias Supply Voltage
(MAX6931 Only)
V
-11
0
V
V
SS
Total Supply Voltage
(MAX6931 Only)
V
- V
76
BB
SS
T
A
T
A
T
A
T
A
T
A
T
A
T
A
T
A
T
A
T
A
T
A
T
A
T
A
T
A
T
A
T
A
T
A
T
A
T
A
T
A
= +25°C
78
170
200
900
1000
3.0
All outputs OUT_ low,
CLK = idle
= -40°C to +125°C
= +25°C
Logic Supply Operating Current
Tube Supply Operating Current
I
µA
mA
mA
CC
540
1.65
0.85
All outputs OUT_ high,
CLK = idle
= -40°C to +125°C
= +25°C
All outputs OUT_ low
All outputs OUT_ high
All outputs OUT_ low
All outputs OUT_ high
= -40°C to +125°C
= +25°C
6.9
I
BB
1.3
= -40°C to +125°C
= +25°C
1.4
-0.8
-1.9
-1.4
-1.5
-0.38
-0.87
= -40°C to +125°C
= +25°C
Bias Supply Operating Current
(MAX6931 Only)
I
SS
= -40°C to +125°C
= +25°C
V
- 1.1
BB
V
≥ 15V
BB
= -40°C to +85°C
= -40°C to +125°C
= -40°C to +85°C
= -40°C to +125°C
= +25°C
V
V
V
V
- 2
BB
BB
BB
BB
I
= -25mA
OUT
- 2.5
- 3.5
- 4.0
V
I
≥ 15V
BB
High-Voltage OUT_
V
V
H
= -40mA
OUT
V
- 1.2
BB
8V < V < 15V
BB
= -40°C to +85°C
= -40°C to +125°C
V
V
- 2.5
- 3.0
BB
BB
I
= -25mA
OUT
2
_______________________________________________________________________________________
20-Output, 76V, Serial-Interfaced
VFD Tube Drivers
ELECTRICAL CHARACTERISTICS (continued)
(Typical Operating Circuit, V = 8V to 76V, V
= 3V to 5.5V, V = -11V to 0V, V - V ≤ 76V, T = T
to T
, unless other-
MAX
BB
CC
SS
BB
SS
A
MIN
wise noted.) (Note 1)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
T
T
T
T
T
T
T
T
T
T
T
T
= +25°C
0.75
1
A
A
A
A
A
A
A
A
A
A
A
A
V
≥ 15V
= 1mA
BB
= -40°C to +85°C
= -40°C to +125°C
= +25°C
1.5
I
OUT
1.9
1.1
1.6
2.0
Low-Voltage OUT_
(MAX6921 Only)
V
V
V
L
0.8
8V < V < 15V
BB
= 1mA
= -40°C to +85°C
= -40°C to +125°C
= +25°C
I
OUT
V
+ 0.75 V + 1
SS
SS
V
≥ 15V
= 1mA
BB
= -40°C to +85°C
= -40°C to +125°C
= +25°C
V
V
+ 1.5
+ 1.9
SS
SS
I
OUT
Low-Voltage OUT_
(MAX6931 Only)
V
L
V
+ 0.8 V + 1.1
SS
SS
8V < V < 15V
BB
= 1mA
= -40°C to +85°C
= -40°C to +125°C
V
V
+ 1.6
+ 2.0
2
SS
SS
I
OUT
Rise Time OUT_ (20% to 80%)
Fall Time OUT_ (80% to 20%)
t
V
V
= 60V, C = 50pF, R =2.3kΩ
0.9
0.6
µs
µs
R
BB
BB
L
L
t
= 60V, C = 50pF, R =2.3kΩ
1.5
F
L
L
SERIAL INTERFACE TIMING CHARACTERISTICS
LOAD Rising to OUT_ Falling
Delay
(Notes 2, 3)
0.9
1.2
1.8
2.4
1.8
2.5
10
µs
µs
µs
µs
µA
V
LOAD Rising to OUT_ Rising
Delay
(Notes 2, 3)
(Notes 2, 3)
(Notes 2, 3)
BLANK Rising to OUT_ Falling
Delay
0.9
BLANK Falling to OUT_ Rising
Delay
0.5
1.3
Input Leakage Current
CLK, DIN, LOAD, BLANK
I
, I
0.05
IH IL
Logic-High Input Voltage
CLK, DIN, LOAD, BLANK
0.8 x
V
IH
V
CC
Logic-Low Input Voltage
CLK, DIN, LOAD, BLANK
0.3 x
V
V
IL
V
CC
Hysteresis Voltage
DIN, CLK, LOAD, BLANK
∆V
0.6
V
I
V
0.5
-
CC
High-Voltage DOUT
Low-Voltage DOUT
V
I
I
= -1.0mA
SOURCE
V
V
OH
V
= 1.0mA
SINK
0.5
OL
_______________________________________________________________________________________
3
20-Output, 76V, Serial-Interfaced
VFD Tube Drivers
ELECTRICAL CHARACTERISTICS (continued)
(Typical Operating Circuit, V = 8V to 76V, V
= 3V to 5.5V, V = -11V to 0V, V - V ≤ 76V, T = T
to T
, unless other-
MAX
BB
CC
SS
BB
SS
A
MIN
wise noted.) (Note 1)
PARAMETER
SYMBOL
CONDITIONS
3V to 4.5V
= 10pF
MIN
TYP
60
MAX
100
UNITS
C
DOUT
Rise and Fall Time DOUT
ns
(Note 2)
4.5V to 5.5V
30
80
CLK Clock Period
t
200
90
90
100
5
ns
ns
ns
ns
ns
CP
CLK Pulse-Width High
CLK Pulse-Width Low
CLK Rise to LOAD Rise Hold
DIN Setup Time
t
CH
t
CL
t
(Note 2)
CSH
t
DS
3.0V to 4.5V
4.5V to 5.5V
20
15
25
20
55
DIN Hold Time
t
ns
DH
3.0V to 4.5V
4.5V to 5.5V
120
75
240
150
DOUT Propagation Delay
LOAD Pulse High
t
C
= 10pF
DOUT
ns
ns
DO
t
CSW
Note 1: All parameters are tested at T = +25°C. Specifications over temperature are guaranteed by design.
A
Note 2: Guaranteed by design.
Note 3: Delay measured from control edge to when output OUT_ changes by 1V.
Typical Operating Characteristics
(V
= 5.0V, V = 76V, and T = +25°C, unless otherwise noted.)
A
CC
BB
TUBE SUPPLY CURRENT (I
vs. TEMPERATURE (OUTPUTS LOW)
)
TUBE SUPPLY CURRENT (I )
BB
vs. TEMPERATURE (OUTPUTS HIGH)
LOGIC SUPPLY CURRENT (I
vs. TEMPERATURE (OUTPUTS LOW)
)
BB
CC
2.0
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
400
350
300
250
200
150
100
50
V
= 76V
BB
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
V
= 5V, CLK = 5MHz
CC
V
= 40V
V
= 8V
BB
BB
V
= 3.3V, CLK = 5MHz
= 5V, CLK = IDLE
V
= 76V
CC
BB
V
= 40V
V
BB
CC
V
= 8V
BB
V
= 3.3V, CLK = IDLE
CC
0
-40 -20
0
20 40 60 80 100 120
TEMPERATURE (°C)
-40 -20
0
20 40 60 80 100 120
-40 -20
0
20 40 60 80 100 120
TEMPERATURE (°C)
TEMPERATURE (°C)
4
_______________________________________________________________________________________
20-Output, 76V, Serial-Interfaced
VFD Tube Drivers
Typical Operating Characteristics (continued)
(V
= 5.0V, V = 76V, and T = +25°C, unless otherwise noted.)
BB A
CC
LOGIC SUPPLY CURRENT (I
vs. TEMPERATURE (OUTPUTS HIGH)
)
OUTPUT VOLTAGE (V - V )
vs. TEMPERATURE (OUTPUT HIGH)
CC
BB
H
800
750
700
650
600
550
500
450
400
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
V
= 5V, CLK = 5MHz
I
= -40mA
CC
OUT
V
= 8V
BB
V
= 3.3V, CLK = 5MHz
= 5V, CLK = IDLE
CC
V
= 40V
BB
V
CC
V
= 76V
BB
V
= 3.3V, CLK = IDLE
CC
-40 -20
0
20 40 60 80 100 120
-40 -20
0
20 40 60 80 100 120
TEMPERATURE (°C)
TEMPERATURE (°C)
OUTPUT VOLTAGE
vs. TEMPERATURE (OUTPUT LOW)
OUTPUT RISE AND FALL WAVEFORM
MAX6921/31 toc07
14
12
10
8
I
= 4mA
OUT
V
= 76V
BB
BLANK
2V/div
V
= 40V
BB
6
OUT_
20V/div
V
= 8V
BB
4
2
0
-40 -20
0
20 40 60 80 100 120
1µs/div
TEMPERATURE (°C)
_______________________________________________________________________________________
5
20-Output, 76V, Serial-Interfaced
VFD Tube Drivers
Pin Description
PIN
NAME
FUNCTION
TSSOP
WIDE SO/
PLCC
MAX6931
MAX6921
1–5, 10–19,
24–28
OUT0 to VFD Anode and Grid Drivers. OUT0 to OUT19 are push-pull outputs swinging
OUT19 from V to V
—
—
.
SS
BB
1–5, 10–19,
24–28
3–12,
17–26
OUT0 to VFD Anode and Grid Drivers. OUT0 to OUT19 are push-pull outputs swinging
—
—
6
OUT19
from V to GND.
BB
Serial-Clock Output. Data is clocked out of the internal shift-register to DOUT
on CLK’s rising edge.
9
6
2
DOUT
Serial-Data Input. Data is loaded into the internal shift register on CLK’s rising
edge.
27
DIN
7
8
9
7
8
28
1
V
V
Logic Supply Voltage
CC
VFD Tube Supply Voltage
Filament Bias Supply Voltage
BB
—
—
V
SS
Blanking Input. High forces outputs OUT0 to OUT19 low, without altering the
contents of the output latches. Low enables outputs OUT0 to OUT19 to follow
the state of the output latches.
20
20
13
BLANK
21
22
21
22
14
15
GND
CLK
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.
23
23
16
LOAD
CLK
MAX6921 ONLY
SERIAL-TO-PARALLEL SHIFT REGISTER
LATCHES
DIN
LOAD
DOUT
BLANK
MAX6921
MAX6931
OUT0 OUT1 OUT2
OUT19
Figure 1. MAX6921/MAX6931 Functional Diagram
_______________________________________________________________________________________
6
20-Output, 76V, Serial-Interfaced
VFD Tube Drivers
V
V
BB
BB
40Ω
TYPICAL
40Ω
TYPICAL
SLEW-RATE
CONTROL
SLEW-RATE
CONTROL
OUT_
OUT_
750Ω
TYPICAL
750Ω
TYPICAL
V
SS
Figure 2. MAX6921 CMOS Output Driver Structure
Figure 3. MAX6931 CMOS Output Driver Structure
4-Wire Serial Interface
Detailed Description
The MAX6921/MAX6931 use 4-wire serial interface with
three inputs (DIN, CLK, LOAD) and a data output
(DOUT, MAX6921 only). This interface is used to write
output data to the MAX6921/MAX6931 (Figure 4) (Table
1). The serial interface data word length is 20 bits,
D0–D19.
The MAX6921/MAX6931 are VFD tube drivers compris-
ing a 4-wire serial interface driving 20 high-voltage Rail-
to-Rail output ports. The driver is suitable for both static
and multiplexed displays.
The output ports feature high current-sourcing capabili-
ty to drive current into grids and anodes of static or
multiplex VFDs. The ports also have active current sink-
ing for fast discharge of capacitive display electrodes
in multiplexing applications.
The functions of the four serial interface pins are:
• CLK input is the interface clock, which shifts data
into the MAX6921/MAX6931s’ 20-bit shift register on
its rising edge.
The 4-wire serial interface comprises a 20-bit shift reg-
ister and a 20-bit transparent latch. The shift register is
written through a clock input CLK and a data input DIN.
For the MAX6921, the data propagates to a data output
DOUT. The data output allows multiple drivers to be
cascaded and operated together. The output latch is
transparent to the shift register outputs when LOAD is
high, and latches the current state on the falling edge
of LOAD.
• LOAD input passes data from the MAX6921/
MAX6931s’ 20-bit shift register to the 20-bit output
latch when LOAD is high (transparent latch), and
latches the data on LOAD’s falling edge
• DIN is the interface data input, and must be stable
when it is sampled on the rising edge of CLK.
• DOUT is the interface data output, which shifts data
out from the MAX6921’s 20-bit shift register on the
rising edge of CLK. Data at DIN is propagated
through the shift register and appears at DOUT (20
Each driver output is a slew-rated controlled CMOS
push-pull switch driving between V
and GND
BB
(MAX6921) or V (MAX6931). The output rise time is
SS
CLK cycles + t ) later.
DO
always slower than the output fall time to avoid shoot-
through currents during output transitions. The output
slew rates are slow enough to minimize EMI, yet are
fast enough so as not to impact the typical 100µs digit
multiplex period and affect the display intensity.
A fifth input, BLANK, can be taken high to force outputs
OUT0 to OUT19 low, without altering the contents of the
output latches. When the BLANK input is low, outputs
OUT0 to OUT19 follow the state of the output latches. A
common use of the BLANK input is PWM intensity control.
Initial Power-Up and Operation
An internal reset circuit clears the internal registers of
the MAX6921/MAX6931 on power-up. All outputs OUT0
to OUT19 and the interface output DOUT (MAX6921
only) initialize low regardless of the initial logic levels of
the CLK, DIN, BLANK, and LOAD inputs.
The BLANK input’s function is independent of the oper-
ation of the serial interface. Data can be shifted into the
serial interface shift register and latched regardless of
the state of BLANK.
Rail-to-Rail is a registered trademark of Nippon Motorola, Ltd.
_______________________________________________________________________________________
7
20-Output, 76V, Serial-Interfaced
VFD Tube Drivers
t
CSW
LOAD
t
CSH
t
t
CH
CL
t
CP
CLK
DIN
t
DH
t
DS
D19
D18
D1
D0
t
DO
DOUT
D19
Figure 4. 4-Wire Serial Interface Timing Diagram
Table 1. 4-Wire Serial Interface Truth Table
CLOCK
INPUT
LOAD
INPUT
BLANKING
INPUT
SERIAL
DATA
INPUT
DIN
SHIFT REGISTER CONTENTS
LATCH CONTENTS
OUTPUT CONTENTS
CLK D0 D1 D2 … Dn-1 Dn
LOAD D0 D1 D2
…
Dn-1 Dn
BLANK
D0 D1 D2
…
Dn-1 Dn
H
L
H
L
R0 R1 … Rn-2 Rn-1
R0 R1 … Rn-2 Rn-1
X
R0 R1 R2 … Rn-1 Rn
X
X
X
…
X
X
L
R0 R1 R2
P0 P1 P2
…
…
…
Rn-1 Rn
Pn-1 Pn
P0 P1 P2 … Pn-1
Pn
H
L
P0 P1 P2
…
…
Pn-1 Pn
X
X
X
X
X
H
L
L
L
L
L
L = Low logic level.
H = High logic level.
X = Don’t care.
P = Present state (shift register).
R = Previous state (latched).
CLK and DIN may be used to transmit data to other
peripherals. Activity on CLK always shifts data into the
MAX6921/MAX6931s’ shift register. However, the
MAX6921/MAX6931 only update their output latch on
the rising edge of LOAD, and the last 20 bits of data
are loaded. Therefore, multiple devices can share CLK
and DIN, as long as they have unique LOAD controls.
Writing Device Registers Using the
4-Wire Serial Interface
The MAX6921/MAX6931 are normally written using the
following sequence:
1) Take CLK low.
2) Clock 20 bits of data in order D19 first to D0 last
into DIN, observing the data setup and hold times.
Determining Driver Output Voltage Drop
The outputs are CMOS drivers, and have a resistive
characteristic. The typical and maximum sink and
source output resistances can be calculated from the
3) Load the 20 output latches with a falling edge
on LOAD.
LOAD may be high or low during a transmission. If
LOAD is high, then the data shifted into the shift regis-
ter at DIN appear at the OUT0 to OUT19 outputs.
V
and V electrical characteristics. Use this calculated
L
H
resistance to determine the output voltage drop at dif-
ferent output currents.
8
_______________________________________________________________________________________
20-Output, 76V, Serial-Interfaced
VFD Tube Drivers
of the resistor can be determined by the load capaci-
tance and timing characteristics required. Resistor R
discharges tube capacitance C to 10% of the initial
voltage in 2.3 x RC seconds. So, for example, a 15kΩ
value for R discharges 100pF tube grid or anode from
40V to 4V in 3.5µs, but draws an additional 2.7mA from
the driver when either output is high.
Output Current Ratings
The continuous current-source capability is 40mA per
output. Outputs may drive up to 75mA as a repetitive
peak current, subject to the on-time (output high) being
no longer than 1ms, and the duty cycle being such that
the output power dissipation is no more than the dissipa-
tion for the continuous case. The repetitive peak rating
allows outputs to drive a higher current in multiplex grid
driver applications, where only one grid is on at a time,
and the multiplex time per grid is no more than 1ms.
Power Dissipation
Take care to ensure that the maximum package dissi-
pation ratings for the chosen package are not exceed-
ed. Over-dissipation is unlikely to be an issue when
driving static tubes, but the peak currents are usually
higher for multiplexed tubes. When using multiple dri-
ver devices, try to share the average dissipation evenly
between the drivers.
Since dissipation is proportional to current squared, the
maximum current that can be delivered for a given mul-
tiplex ratio is given by:
I
= (grids x 1600)1/2 mA
PEAK
where grids is the number of grids in a multiplexed
display.
Determine the power dissipation (P ) for the
D
MAX6921/MAX6931 for static tube drivers with the fol-
lowing equation:
This means that a duplex application (two grids) can use
a repetitive peak current of 56.5mA, a triplex (three grids)
application can use a repetitive peak current of 69.2mA,
and higher multiplex ratios are limited to 75mA.
P
D
= (V
x I ) + (V x I ) + ((V - V ) x
CC CC BB BB BB H
I
x A))
ANODE
where:
Paralleling Outputs
Any number of outputs within the same package may
be paralleled in order to raise the current drive or
reduce the output resistance. Only parallel outputs
directly (by shorting outputs together) if the interface
control can be guaranteed to set the outputs to the
same level. Although the sink output is relatively weak
(typically 750Ω), that resistance is low enough to dissi-
pate 530mW when shorted to an opposite level output
A = number of anodes driven (the MAX6921/MAX6931
can drive a maximum of 20).
I
= maximum anode current.
ANODE
(V - V ) is the output voltage drop at the given maxi-
BB
H
mum anode current I
.
OUT
A static tube dissipation example follows:
V
CC
= 5V 5%, V = 10V to 18V, A = 20, I
= 2mA
OUT
BB
at a V voltage of only 20V. A safe way to parallel out-
BB
PD = (5.25V x 1mA)+ (18V x 1.4mA) +
((2.5V x 2mA/25mA) x 2mA x 20) = 38mW
puts is to use diodes to prevent the outputs from sink-
ing current (Figure 5). Because the outputs cannot sink
current from the VFD tube, an external discharge resis-
tor, R, is required. For static tubes, R can be a large
value such as 100kΩ. For multiplexed tubes, the value
Determine the power dissipation (P ) for the MAX6921/
D
MAX6931 for multiplex tube drivers with the following
equation:
P
D
= (V
x I ) + (V x I ) + ((V - V ) x
CC CC BB BB BB H
I
x A) + ((V - V ) x I
))
GRID
ANODE
BB
H
where:
A = number of anodes driven.
G = number of grids driven.
MAX6921
MAX6931
D1
OUT0
OUTPUT
I
= maximum anode current.
ANODE
D2
I
= maximum grid current.
GRID
OUT1
The calculation presumes all anodes are on, but only
one grid is on. The calculated P is the worst case,
D
R
presuming one digit is always being driven with all its
anodes lit. Actual P can be estimated by multiplying
D
this P figure by the actual tube drive duty cycle, taking
D
into account interdigit blanking and any PWM intensity
control.
Figure 5. Paralleling Outputs
_______________________________________________________________________________________
9
20-Output, 76V, Serial-Interfaced
VFD Tube Drivers
A multiplexed tube dissipation example follows:
Typical Application Circuit
V
CC
= 5V 5%, V = 36V to 42V, A = 12, G = 8,
BB
I
= 0.4mA, I
= 24mA
GRID
ANODE
P
D
= (5.25V x 1mA)+ (42V x 1.4mA) +
((2.5V x 0.4mA/25mA) x 0.4mA x 12) +
((2.5V x 24mA/25mA) x 24mA) = 122mW
MAX685x
MAX6921
VFDOUT
DIN
Thus, for a 28-pin wide TSSOP package (T = 1 / 0.0128
JA
VFCLK
CLK
= 78.125°C/W from Absolute Maximum Ratings), the
maximum allowed ambient temperature T is given by:
A
VFLOAD
LOAD
BLANK
T
= T + (P x T ) = 150°C = T + (0.122 x
A D JA A
78.125°C/W)
J(MAX)
VFBLANK
DOUT
DOUT
DOUT
So T = +140.5°C.
A
This means that the driver can be operated in this
application up to the MAX6921/MAX6931s’ +125°C
maximum operating temperature.
MAX6921
DIN
Power-Supply Considerations
CLK
The MAX6921/MAX6931 operate with multiple power-
LOAD
BLANK
supply voltages. Bypass the V , V , and V
SS
CC
BB
(MAX6931 only) power-supply pins to GND with 0.1µF
capacitors close to the device. The MAX6931 may be
operated with V tied to GND if a negative bias supply
SS
is not required. For multiplex applications, it may be
necessary to add an additional bulk electrolytic capaci-
tor of 1µF or greater to the V supply.
MAX6921
BB
DIN
Power-Supply Sequencing
CLK
The order of the power-supply sequencing is not impor-
tant. The MAX6921/MAX6931 will not be damaged if
any combination of V , V , and V (MAX6931 only)
LOAD
BLANK
CC BB
SS
is grounded while the other supply or supplies are
maintained up to their maximum ratings. However, as
with any CMOS device, do not drive the MAX6921/
MAX6931s’ logic inputs if the logic supply V
is not
CC
operational because the input protection diodes clamp
the signals.
Chip Information
TRANSISTOR COUNT: 2743
PROCESS: BiCMOS
Cascading Drivers (MAX6921 Only)
Multiple MAX6921s may be cascaded, as shown in the
Typical Application Circuit, by connecting each driver’s
DOUT to DIN of the next drivers. Devices may be cas-
caded at the full 5MHz CLK speed when V
≥ 4.5V.
CC
When V
<4.5V, the longer propagation delay (t
)
DO
CC
limits the maximum cascaded CLK to 4MHz.
10 ______________________________________________________________________________________
20-Output, 76V, Serial-Interfaced
VFD Tube Drivers
Pin Configurations
TOP VIEW
OUT4
OUT3
OUT2
OUT1
OUT0
DIN
1
2
3
4
5
6
7
8
9
28 OUT5
27 OUT6
26 OUT7
25 OUT8
24 OUT9
23 LOAD
22 CLK
OUT4
OUT3
OUT2
OUT1
OUT0
DIN
1
2
3
4
5
6
7
8
9
28 OUT5
27 OUT6
26 OUT7
25 OUT8
24 OUT9
23 LOAD
22 CLK
V
1
2
3
4
5
6
7
8
9
28 V
CC
BB
DOUT
OUT19
OUT18
OUT17
OUT16
OUT15
OUT14
OUT13
27 DIN
26 OUT0
25 OUT1
24 OUT2
23 OUT3
22 OUT4
21 OUT5
20 OUT6
19 OUT7
18 OUT8
17 OUT9
16 LOAD
15 CLK
MAX6921AUI
MAX6931AUI
MAX6921AWI
V
V
CC
CC
V
BB
21 GND
V
BB
V
SS
21 GND
DOUT
20 BLANK
19 OUT10
18 OUT11
17 OUT12
16 OUT13
15 OUT14
20 BLANK
19 OUT10
18 OUT11
17 OUT12
16 OUT13
15 OUT14
OUT19 10
OUT18 11
OUT17 12
OUT16 13
OUT15 14
OUT19 10
OUT18 11
OUT17 12
OUT16 13
OUT15 14
OUT12 10
OUT11 11
OUT10 12
BLANK 13
GND 14
SO
TSSOP
TSSOP
4
3
2
1
28 27 26
OUT1
OUT17
OUT16
OUT15
OUT14
OUT13
OUT12
OUT11
5
6
25
24
23
22
OUT2
OUT3
OUT4
7
8
MAX6921AQI
9
21 OUT5
20 OUT6
19 OUT7
10
11
12 13 14 15 16 17 18
PLCC
______________________________________________________________________________________ 11
20-Output, 76V, Serial-Interfaced
VFD Tube Drivers
Package Information
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information,
go to www.maxim-ic.com/packages.)
12 ______________________________________________________________________________________
20-Output, 76V, Serial-Interfaced
VFD Tube Drivers
Package Information (continued)
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information,
go to www.maxim-ic.com/packages.)
INCHES
MILLIMETERS
N
MIN
MAX
0.104
0.012
0.019
0.013
MIN
2.35
0.10
0.35
0.23
MAX
2.65
0.30
0.49
0.32
DIM
A
0.093
0.004
0.014
0.009
A1
B
C
e
0.050
1.27
E
H
E
0.291
0.394
0.016
0.299
0.419
0.050
7.40
10.00
0.40
7.60
10.65
1.27
H
L
VARIATIONS:
INCHES
1
MILLIMETERS
TOP VIEW
DIM
D
MIN
MAX
0.413
0.463
0.512
0.614
0.713
MIN
10.10
11.35
12.60
15.20
17.70
MAX
N MS013
0.398
0.447
0.496
0.598
0.697
10.50 16 AA
11.75 18 AB
13.00 20 AC
15.60 24 AD
18.10 28 AE
D
D
D
D
D
C
A
B
e
0 -8
A1
L
FRONT VIEW
SIDE VIEW
PROPRIETARY INFORMATION
TITLE:
PACKAGE OUTLINE, .300" SOIC
APPROVAL
DOCUMENT CONTROL NO.
REV.
1
21-0042
B
1
______________________________________________________________________________________ 13
20-Output, 76V, Serial-Interfaced
VFD Tube Drivers
Package Information (continued)
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information,
go to www.maxim-ic.com/packages.)
e
INCHES
MIN MAX MIN
D 0.385 0.395 9.78
D1 0.350 0.356 8.89
D2 0.290 0.330 7.37
INCHES
MIN MAX MIN
0.165 0.180 4.20
MAX
10.03
9.04
N
MAX
4.57
3.04
3.96
---
0.53
0.81
0.28
20 AA
A
A1 0.090 0.120 2.29
A2 0.145 0.156 3.69
8.38
D D1 D3
A3 0.020 ---
0.013 0.021 0.33
B1 0.026 0.032 0.66
0.51
D3 0.200 REF
5.08 REF
B
N
28 AB
44 AC
52 AD
68 AE
D
0.485 0.495 12.32 12.57
D1 0.450 0.456 11.43 11.58
D2 0.390 0.430 9.91 10.92
D3 0.300 REF 7.62 REF
C
e
0.009 0.011 0.23
0.050 1.27
D3
D1
D
D
0.685 0.695 17.40 17.65
D1 0.650 0.656 16.51 16.66
D2 0.590 0.630 14.99 16.00
D3 0.500 REF
12.70 REF
D
0.785 0.795 19.94 20.19
D1 0.750 0.756 19.05 19.20
D2 0.690 0.730 17.53 18.54
A2
A
A1
D3 0.600 REF
15.24 REF
B1
B
D
0.985 0.995 25.02 25.27
D1 0.950 0.958 24.13 24.33
D2 0.890 0.930 22.61 23.62
C
D2
A3
D3 0.800 REF
20.32 REF
NOTES:
1. D1 DOES NOT INCLUDE MOLD FLASH.
2. MOLD FLASH OR PROTRUSIONS NOT TO EXCEED
.20mm (.008") PER SIDE.
3. LEADS TO BE COPLANAR WITHIN .10mm.
4. CONTROLLING DIMENSION: MILLIMETER
5. MEETS JEDEC MO047-XX AS SHOWN IN TABLE.
6. N = NUMBER OF PINS.
PROPRIETARY INFORMATION
TITLE:
FAMILY PACKAGE OUTLINE:
20L, 28L, 44L, 52L, 68L PLCC
APPROVAL
DOCUMENT CONTROL NO.
REV.
1
21-0049
D
1
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
14 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
© 2003 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products.
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