Nixie Tube Driver



74141 Decoder IC:
The 74141 BCD to decimal decoder and Nixie driver IC is still available at time of writing, but the situation is likely to change. A few years ago it and was manufactured* by NTE Electronics (part no. NTE74141), and marketed by Mouser Electronics, but recently it seems to have disappeared from the Mouser website. For other sources, see useful links on the Nixie tube page (particularly Dönberg Electronics).

(* The 'manufacturing' process has been noted by some observers to involve erasing the markings on NOS Texas chips and re-marking them as new parts).

SN74141 Data:
· Drives gas-filled cold-cathode indicator tubes directly.
· Fully decoded inputs ensure all outputs are off for invalid codes.
· Input clamping diodes minimise transmission-line effects.

Full decoding is provided for all possible input states. For hexadecimal inputs A - F, all the outputs are off. Therefore, the 74141 can use these invalid codes to blank leading or trailing zeros in a display.

The high-voltage NPN output transistors have a maximum leakage current of 50μA at 55V.
Power dissipation: 80mW typ.
Truth Table
Input Output
on
(low)
D C B A
0 0 0 0 0
0 0 0 1 1
0 0 1 0 2
0 0 1 1 3
0 1 0 0 4
0 1 0 1 5
0 1 1 0 6
0 1 1 1 7
1 0 0 0 8
1 0 0 1 9
1 0 1 0 none
1 0 1 1 none
1 1 0 0 none
1 1 0 1 none
1 1 1 0 none
1 1 1 1 none


Equivalent Circuit:


Absolute maximum ratings over operating free-air temperature range:
Supply Voltage Vcc 7 V
Input voltage 5.5 V
Current into any output (off state) 2 mA
Operating free-air temp. range 0°C to 70°C
Storage temp. range -65°C to 150°C


Recommended operating conditions: Min Nom Max Unit
Supply Voltage Vcc 4.75 5 5.25 V
Off-state output voltage     60 V
Free-air temp TA 0   70 °C


Electrical characteristics over recommended operating free-air temp. range:
Parameter Test Conditions Min Typ Max Unit
VIH High-level input Voltage   2     V
VIL Low-level input voltage       0.8 V
VIK Input clamp voltage Vcc = 4.75, II = -5mA     -1.5 V
Vo(on) On-state output voltage Vcc = 4.75, Io = 7mA     2.5 V
Vo(off) Off-state output voltage
for input counts 0 - 9		 Vcc = 5.25, Io = 0.5mA 60     V
Io(off) Off-state reverse current Vcc = 5.25, Vo = 55V     50 μA
Io(off) Off state reverse current
for input counts (Hex) A - F		 Vcc = 5.25
Vo = 30V		 TA = 55°C     5 μA
TA = 70°C     15
I1 Input current at max. input voltage Vcc = 5.25, VI = 5.5V     1 mA
IIH High-level input current Input A Vcc = 5.25, VI = 2.4V     40 μA
Input B, C, D     80
IIL Low-level input current Input A Vcc = 5.25, VI = 0.4V     -1.6 mA
Input B, C, D     -3.2
Icc Supply Current (all inputs grounded and outputs open). Vcc = 5V, TA = 25°C   16   mA
Vcc = 5.25     25




Note on the SN7441:
In equipment manufactured prior to about 1970, you may come across Nixie tubes driven by the 7441 IC. The 7441 is the original BCD to Decimal decoder / driver offered by TI. It differs from the 74141 in that the input signals are not fully decoded, ie., it will output nonsense (several cathodes on at once if I recall rightly) on reciept of Hex inputs A - F. This was found to be a pain when using digital counters in conjunction with valve / tube oscillators (because BCD counters often contain invalid counts at switch-on and don't get corrected until the oscillator starts), and the device was quickly superceded by the 74141. The 7441 is pin compatible with the 74141 and can be replaced by it, provided that the original circuit designer hasn't done something clever (ie., stupid) involving the invalid codes.


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