WRM_C.qxd 28/4/03 10:02 am Page 1 Mini Melf Resistors Welwyn Components WRM Series * High reliability * Predictable pulse handling capability * Tolerances down to 0.1% * TCR down to 5 ppm/C Electrical Data WRM 0102 WRM 0204 WRM 0207 Power rating at 70C watts 0.2 0.25 0.4 Resistance range ohms R22 - 2M21 R22 - 10M R22 - 8M2 Limiting element voltage volts TCR ppm/C Resistance tolerance 150 200 300 15, 25, 50 5, 15, 25, 50 25, 50 % 0.1, 0.25, 0.5, 1.0 Standard values E24 & E96 Thermal impedance k/W Ambient temperature range 250 C Insulation resistance 200 140 -55 to +125 >1010 ohms Physical Data Dimensions (mm) and weight (g) L L1 D D1 D1 K K Weight max min max max min max min t per unit WRM 0102 2.2 1.2 1.1 1.1 1.06 0.45 0.35 0.01 WRM 0204 3.6 1.8 1.4 1.4 1.25 0.85 0.5 0.02 WRM 0207 5.8 2.8 2.2 2.2 2.0 1.4 1.1 0.08 Type L D D1 L1 K Construction Terminations A metal film is deposited onto a high dissipation ceramic former to which solder plated teminating caps are fitted. Material Plated steel cap. Solderability The terminal caps have a multi-layer coating of nickel-copper-nickel and pure tin. The pure tin finish produces ageing free contacts on which low melting solders can be used. Dipped area shall be covered with a smooth and bright solder coating after 3 seconds immersion at 215C. The resistor is adjusted to value by a helical cut in the film and the body is protected by a lacquer coating. Marking Resistance values are colour coded with 5 bands. The TCR is also colour coded as detailed below. TCR 50 ppm - No Dot TCR 25 ppm - Yellow Dot TCR 15 ppm - Orange Dot Solvent Resistance The body protection and marking are resistant to all normal industrial cleaning solvents suitable for printed circuit boards. General Note Welwyn Components reserves the right to make changes in product specification without notice or liability. All information is subject to Welwyn's own data and is considered accurate at time of going to print. (c) Welwyn Components Limited * Bedlington, Northumberland NE22 7AA, UK Telephone: +44 (0) 1670 822181 * Facsimile: +44 (0) 1670 829465 * Email: info@welwyn-tt.com * Website: www.welwyn-tt.com A subsidiary of TT electronics plc Issue C * 04.03 39 WRM_C.qxd 28/4/03 10:02 am Page 2 Mini Melf Resistors Welwyn Components WRM Series TCR and Tolerance Range Type TCR Tolerance Reference Tolerance Professional Precision 5% 2% 1.0% 0.5% 0.25% 0.1% 47RS - 221K 100R - 221K - WRM0102 50ppm R22 - R91 IRO - 9R1 10R - 2.21M WRM0102 25ppm - - 10R - 221K 47R5 - 221K 100R - 221K 100R - 100K WRM0102 15ppm - - - 100R - 100K 100R - 100K 100R - 100K WRM0102 10ppm - - - - - - WRM0102 05ppm - - - - - - WRM0204 50ppm R22 - R91 - 1R - 10M 10R - 475K 22R - 332K 43R - 332K WRM0204 25ppm - - 10R - 475K 10R - 475K 22R - 332K 43R - 332K WRM0204 15ppm - - - 10R - 221K 22R - 221K 43R - 221K WRM0204 10ppm - - - - 22R - 221K 43R - 221K WRM0204 05ppm - - - - 100R - 100K 100R - 100K WRM0207 50ppm R22 - R91 - 1R - 8.2M 10R - 1M - - WRM0207 25ppm - - - 10R - 1M - - WRM0207 15ppm - - - - - - WRM0207 10ppm - - - - - - WRM0207 05ppm - - - - - - * TC 10ppm & 5ppm is specified over the temperature range -10C to +85C. Performance Data Results R/R Test Stability class Description 0.25 0.5 1.0 10 - <75 0.22 - <10 75 - <100 k >100 k - 332 k >332 k - 10 M Short time overload* 0.05% + 0.01 0.1% + 0.01 0.25% + 0.05 Bending test* 0.05% + 0.01 0.1% + 0.01 0.25% + 0.05 Resistance to soldering heat 0.05% + 0.01 0.1% + 0.01 0.25% + 0.05 Temperature rapid change 0.05% + 0.01 0.1% + 0.01 0.25% + 0.05 0.25% + 0.05 0.25% + 0.05 0.5% + 0.05 Endurance* Load life 1000h 0.5% + 0.05 0.5% + 0.05 1.0% + 0.05 Climatic sequence* 0.25% + 0.05 0.5% + 0.05 1.0% + 0.05 Damp heat steady state* 0.25% + 0.05 0.5% + 0.05 1.0% + 0.05 < 0.25 V/V < 3 V/V 8000 h Current noise Solderability < 0.05 V/V Dipped area shall be covered with a smooth and bright solder coating of at least 96% Voltage coefficient Voltage proof < 0.5 . 106/V No flashover or breakdown * Resistors to be mounted on a PC-board according to IEC 115-1, clause 4.27.1 (c) Welwyn Components Limited Bedlington, Northumberland NE22 7AA, UK Telephone: +44 (0) 1670 822181 * Facsimile: +44 (0) 1670 829465 * Email: info@welwyn-tt.com * Website: www.welwyn-tt.com 40 Issue C * 04.03 28/4/03 10:02 am Page 3 Mini Melf Resistors Welwyn Components WRM Series Pulse Handling Information The permissible pulse load is determined by the resistance change as given for the endurance test after 8000 hours. 1 Pulse Voltage Limit Vmax is the The maximum permissible impulse voltage Vmax voltage pulse short overload depending on the impulse time ti. High ohmic values are protected by the interdependence of voltage limit and impulse time. This function is given by the equation. Vmax 2,5 . Vmax = + Vmax 1 + ti . K That means: R nominal resistance values tp time of the pulse period (t -1 p = pulse frequency) V (t) pulse voltage V peak voltage of the pulse P rated dissipation of the resistor at ambient temperature t2 - t1 impulse time ti 3 Continuous and Single Pulse Load There is a difference between repetitive pulse load (P = Vmax = maximum permissible continuous voltage, ti = pulse time and K = 100 s-1. ti . P , with = power at the pulse time ti) tp ~ or single pulse load (eg switching events P -> 0). A higher pulse load Pmax is accepted in the latter case. 2 Maximum Pulse Load The average load P P must not exceed the rated dissipation. For resistance values above the critical resistance the rated dissipation is given by the resistance value and the limiting element voltage Vmax. It is required P = t2 V 2 (t) dt P 1 tp . R t1 4 Pulse Shapes The diagrams show the maximum pulse load for a rectangular pulse shape. t . V2 P = i . tp R Other pulses should be converted into rectangular pulse shape, having the same energy at given peak voltage. For exponential pulses the calculation follows: P = e . V 2 2 . tp R with e = R . C or e = V L R V ti ti e 0,37 . V WRM_C.qxd t1 t2 Rectangular Pulses t t Exponential Pulse (c) Welwyn Components Limited Bedlington, Northumberland NE22 7AA, UK Telephone: +44 (0) 1670 822181 * Facsimile: +44 (0) 1670 829465 * Email: info@welwyn-tt.com * Website: www.welwyn-tt.com Issue C * 04.03 41 WRM_C.qxd 28/4/03 10:02 am Page 4 Mini Melf Resistors Welwyn Components WRM Series Single Pulse Maximum Pulse Load WRM 0102 WRM 0204 WRM 0207 Pulse Load Pmax 100 W 10 1 0,1 10 s 100 s 1 ms 10 ms 100 ms 1s 10 s Pulse Duration ti Continuous Pulses Continuous Pulse Load Pmax Maximum Pulse Load WRM 0102 WRM 0204 WRM 0207 100 W 10 1 0,1 10 s 100 s 1 ms 10 ms 100 ms 1s 10 s Pulse Duration ti Packaging The WRM 0102 and 0204 resistors are supplied reeled on 8mm blister tape. WRM 0207 resistors are supplied on 12mm blister tape. Packaging complies with the requirements of IEC 286-3. Bulk packaging is also available on request. (c) Welwyn Components Limited Bedlington, Northumberland NE22 7AA, UK Telephone: +44 (0) 1670 822181 * Facsimile: +44 (0) 1670 829465 * Email: info@welwyn-tt.com * Website: www.welwyn-tt.com 42 Issue C * 04.03