SERIES
MAGNETIC-LATCHING
ESTABLISHED RELIABILITY
TO-5 RELAYS
SPDT
SERIES
DESIGNATION
421
421D
421DD
SPDT basic relay
SPDT relay with internal diode for coil transient suppression
SPDT relay with internal diodes for coil transient suppression and polarity
reversal protection
RELAY TYPE
421
DESCRIPTION
The magnetic-latching TO-5 relay, originally conceived and
developed by Teledyne, has become one of the industry standards
for low-level switching from dry circuit to 0.5 ampere. Designed for
high-density PC board mounting, its small size and low coil power
dissipation make the 421 relay one of the most versatile
ultraminiature relays available.
The following unique construction features and manufacturing
techniques provide excellent resistance to environmental extremes
and overall high reliability:
• All welded construction.
• Unique uni-frame design providing high magnetic efficiency and
mechanical rigidity.
• High force/mass ratios for resistance to shock and vibration.
• Advanced cleaning techniques provide maximum assurance of
internal cleanliness.
• Precious metal alloy contacts material with gold plating assures
excellent high current and dry circuit switching capabilities.
The Series 421D and 421DD utilize discrete silicon diodes for coil
suppression and polarity reversal protection.
By virtue of its inherently low intercontact capacitance and contact
circuit losses, the 421 relay has proven to be an excellent
ultraminiature RF switch for frequency ranges well into the UHF
spectrum. A typical RF application for this TO-5 relay is in handheld
radio transceivers, wherein the combined features of good RF
performance, small size, low coil power dissipation and high
reliability make it a preferred method of transmit-receive switching
(see Figure 1).
The Series 421 magnetic-latching relays are ideally suited for
applications where coil power dissipation must be minimized. The
relays can be operated with a short duration pulse. After the contacts
have transferred, no external holding power is required.
The magnetic latching feature of the Series 421 provides a “memory”
capability, since the relays will not reset upon removal of coil power.
PERMANENT MAGNET
MAGNETIC CIRCUIT A
SOFT IRON CORE A
PRINCIPLE OF OPERATION
MAGNETIC CIRCUIT B
Energizing Coil B produces a magnetic field
COIL A
COIL B
opposing the holding flux of the permanent magnet
SOFT IRON
in Circuit B. As this net holding force decreases, the
SOFT IRON
CORE A
CORE B
attractive force in the air gap of Circuit A, which also
AIR GAP
results from the flux of the permanent magnet,
SOFT IRON
ARMATURE
MOVING
CONTACT
becomes great enough to break the armature free
of Core B, and snap it into a closed position against
Core A. The armature then remains in this position
STATIONARY
CONTACT
upon removal of power from Coil B, but will snap
back into position B upon energizing Coil A. Since operation depends upon cancellation
of a magnetic field, it is necessary to apply the correct polarity to the relay coils as
indicated on the relay schematic. When latching relays are installed in equipment, the
latch and reset coils should not be pulsed simultaneously. Coils should not be pulsed
with less than rated coil voltage and the pulse width should be a minimum of three times
the specified operate time of the relay. If these conditions are not followed, it is possible
for the relay to be in the magnetic neutral position.
ENVIRONMENTAL AND
PHYSICAL SPECIFICATIONS
Temperature
(Ambient)
Vibration
(General Note 1)
Shock
(General Note 1)
Acceleration
Enclosure
Weight
–65°C to +125°C
30 g’s to 3000 Hz
100 g’s,
6 msec, half-sine
50 g’s
Hermetically sealed
0.089 oz. (2.52g) max.
©2005 TELEDYNE RELAYS
421/1205/Q1
421 Page 1
SPECIFICATIONS ARE SUBJECT TO CHANGE WITHOUT NOTICE
www.teledynerelays.com
SERIES 421
GENERAL ELECTRICAL SPECIFICATIONS (–65°C to +125°C unless otherwise noted) (Notes 2 & 3)
Contact Arrangement
Rated Duty
Contact Resistance
Contact Load Ratings (DC)
(See Fig. 2 for other DC
resistive voltage/current ratings)
Contact Load Ratings (AC)
Contact Life Ratings
Contact Overload Rating
Contact Carry Rating
Coil Operating Power
Operate Time
Contact Bounce
Minimum Operate Pulse
Intercontact Capacitance
Insulation Resistance
Dielectric Strength
Negative Coil Transient (Vdc)
Diode P.I.V. (Vdc)
1 Form C (SPDT)
Continuous
0.125 ohm max. before life; 0.225 ohm max. after life at 0.5A/28Vdc (measured 1/8" from header)
Resistive:
Inductive:
Lamp:
Low Level:
Resistive:
0.5 Amp/28Vdc
200 mA/28Vdc (320 mH)
100 mA/28Vdc
10 to 50 µA/10 to 50mV
250 mA/115Vac, 60 and 400 Hz (Case not grounded)
100 mA/115Vac, 60 and 400 Hz (Case grounded)
10,000,000 cycles (typical) at low level
100,000 cycles min. at all other loads specified above
1A/28Vdc Resistive (100 cycles min.)
Contact factory
290 milliwatts typical at nominal rated voltage @ 25°C
1.5 msec max. at nominal rated coil voltage
1.5 msec max.
4.5 msec width @ rated voltage
0.4 pf typical
10,000 megohms min. between mutually isolated terminals
Atmospheric pressure: 500 Vrms/60Hz
70,000 ft.: 125 Vrms/60Hz
421D/421DD
1.0 max
421D/421DD
100 min.
DETAILED ELECTRICAL SPECIFICATIONS (–65°C to +125°C unless otherwise noted) (Note 3)
BASE PART
NUMBERS
(See Note 8 for full P/N example)
Coil Voltage (Vdc)
Coil Resistance
(Ohms ±10% @25°C)
Coil Current (mAdc @25°C)
(421DD Series only)
Set & Reset Voltage
(Vdc, Max.)
Nom.
Max.
421/421D
421DD (Note 4)
Min.
Max.
421
421D
421DD
421-5
421D-5
421DD-5
5.0
6.0
61
48
78.0
111.8
3.5
3.7
4.5
421-6
421D-6
421DD-6
6.0
8.0
120
97
45.8
63.0
4.5
4.5
5.5
421-9
421D-9
421DD-9
9.0
12.0
280
280
25.7
34.9
6.8
6.8
7.8
421-12
421D-12
421DD-12
12.0
16.0
500
500
19.6
26.7
9.0
9.0
10.0
421-18
421D-18
421DD-18
18.0
24.0
1130
1130
13.4
18.8
13.5
13.5
14.5
421-26
421D-26
421DD-26
26.5
32.0
2000
2000
11.2
15.2
18.0
18.0
19.0
PERFORMANCE CURVES
(NOTE 2)
TYPICAL RF PERFORMANCE
TYPICAL DC CONTACT RATING (RESISTIVE)
0
.1
.2
.3
.4
dB
LOAD VOLTAGE (VDC)
300
INSE
RTIO
N LO
SS
250
200
150
100
50
10
20
30
40
50
60
70
.01
0.5
.1
.5
1.0
FREQUENCY (GHz)
NA
ATIO
ISOL
C
C
ROSS
1.92
R
S (V
N LOS
ETUR
SWR)
1.22
CTS
ONTA
1.02
1.01
1.00
1.00
VSWR
1.07
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
LOAD CURRENT (AMPS DC)
FIGURE 1
FIGURE 2
©2005 TELEDYNE RELAYS
SPECIFICATIONS ARE SUBJECT TO CHANGE WITHOUT NOTICE
www.teledynerelays.com
421 Page 2
421/1205/Q1
SERIES 421
OUTLINE DIMENSIONS
CASE DETAIL
.370
(9.40)
DIA. MAX.
.335
(8.51)
DIA. MAX.
.035 (.89)
±.010 (0.25)
SCHEMATIC DIAGRAMS
TERMINAL LOCATIONS AND PIN NUMBERING (REF. ONLY)
(Viewed from Terminals)
.031 (.79)
±.003 (0.08)
36° ±3°
TYP.
COIL B
COIL A
9
8
7
6
1
2
4
COIL B
421
.280 (7.11) MAX.
WIRE LEAD: .75 (19.05) MIN.
PIN: .187 (4.75) ±.010 (.25)
(See Note 6)
+.002 (.05)
.017 (.43) –.001 (.03) DIA.
.200 (5.08)
±.010 (.25) DIA.
DIMENSIONS ARE SHOWN IN INCHES (MILLIMETERS)
COIL A
GENERAL NOTES
1. Relay contacts will exhibit no chatter in excess of 10 µsec or transfer in excess of 1
µsec.
2. “Typical” characteristics are based on available data and are best estimates. No
on-going verification tests are performed.
3. Unless otherwise specified, parameters are initial values.
4. For reference only. Coil resistance not directly measurable at relay terminals due to
internal series diode, 421DD only.
5. Unless otherwise specified, relays will be supplied with either gold-plated or solder-
coated leads.
6. The slash and characters appearing after the slash are not marked on the relay.
7. Screened HI-REL versions available. Contact factory.
8.
COIL B
421D
COIL A
421DD
SCHEMATICS ARE VIEWED FROM TERMINALS
COIL A LAST ENERGIZED
Teledyne Part Numbering System for
T
2
R
® Established Reliability Relay
ER 421 X M3 - 26 A / S Q
Established Reliability
Designator
Relay Series
Optional Ground Pin
(See Appendix)
Pad Option
(See Appendix)
Q= Solder Coated Leads
G= Gold Plated Leads
(Notes 5 and 6)
S= 0.187" leads
(Note 6)
Screening and Reliability
Level
Coil Voltage
Teledyne Part Numbering System for Military Qualified (JAN) Relays
J
421 X
M - 26 P
L
Screening and Reliability
Level
Terminal Variant
P = 0.187"
Coil Voltage
Military (JAN)
Designator
Relay Series
Optional Ground Pin
(See Appendix)
Pad Option
(See Appendix)
JAN part number example is for reference only. Actual part number may not exist.
421 Page 3
SPECIFICATIONS ARE SUBJECT TO CHANGE WITHOUT NOTICE
www.teledynerelays.com
©2005 TELEDYNE RELAYS
421/1205/Q1
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