Details, datasheet, quote on part number: MC3334P
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Features, Applications

This device is designed to use the signal from a reluctor type ignition pickup to produce a well controlled output from a power Darlington output transistor. Very Low Peripheral Component Count

No Critical System Resistors Wide Supply Voltage Operating Range 24 V) Overvoltage Shutdown (30 V) Dwell Automatically Adjusts to Produce Optimum Stored Energy without Waste Externally Adjustable Peak Current Available in Chip and Flip­Chip Form Transient Protected Inputs and Outputs

Rating Power Supply Voltage­Steady State Transient ms or less Output Sink Current­Steady State Transient ms or less Junction Temperature Operating Temperature Range Storage Temperature Range Power Dissipation, Plastic Package, Case 626 Derate above 25°C Symbol Vbat IO(Sink) TJ(max) TA Tstg PD Value 1.25 10 Unit °C W mW/°C

Device to +125°C Operating Temperature Range Package Plastic DIP SO­8 Chip Flip­Chip

Rbat RA 20k Reluctor Pickup ­ C CDwell 3 + Dwell Reference Buffer Current Limit Sense + ­ CFilter 0.1 6 Input Comparator with Hysteresis VCC RDrive 100 Ignition Coil Primary 4.0 Vbat­24 Vdc

Sense *Optional parts for extended transient protection Ground **A 350 V zener clamp is required when using the standard MJ10012. **This clamp is not required if a selected version with VCEO(sus) V is used. 2 1 Power Ground

ELECTRICAL CHARACTERISTICS (TA to +125°C, Vbat = 13.2 Vdc, circuit of Figure 1, unless otherwise noted.)

Figure 2. Ignition Coil Current versus Frequency/Period

The MC3334 high energy ignition circuit was designed to serve aftermarket Delco five­terminal ignition applications. This device, driving a high voltage Darlington transistor, offers an ignition system which optimizes spark energy at minimum power dissipation. The IC is pinned­out to permit thick film or printed circuit module design without any crossovers. The basic function of an ignition circuit is to permit build­up of current in the primary of a spark coil, and then to interrupt the flow at the proper firing time. The resulting flyback action in the ignition coil induces the required high secondary voltage needed for the spark. In the simplest systems, fixed dwell angle produces a fixed duty cycle, which can result in too little stored energy at high RPM, and/or wasted power at low RPM. The MC3334 uses a variable DC voltage reference, stored on CDwell, and buffered to the bottom end of the reluctor pickup (S1) to vary the duty cycle at the spark coil. At high RPM, the MC3334 holds the output "off" for approximately ms to permit full energy discharge from the previous spark; then it switches the output Darlington transistor into full saturation. The current ramps at a slope dictated by Vbat and the coil L. At very high RPM the peak current may be less than desired, but it is limited by the coil itself. As the RPM decreases, the ignition coil current builds up and would be limited only by series resistance losses. The MC3334 provides adjustable peak current regulation sensed by RS and set RD1, in this case A, as shown in Figure 2. As the RPM decreases further, the coil current is held 5.5 A for a short period. This provides a reserve for sudden acceleration, when discharge may suddenly occur earlier than expected. The peak hold period is about 20% at medium RPM, decreasing to about 10% at very low RPM. (Note: = 5000 RPM for an eight cylinder four stroke engine.) At lower Vbat, the "on" period automatically stretches to accommodate the slower current build­up. At very low Vbat and low RPM, a common condition during cold starting, the "on" period is nearly the full cycle to permit as much coil current as possible. The output stage of the IC is designed with an OVP circuit which turns on at Vbat 30 V (VCC 22 V), holding the output Darlington off. This protects the IC and the Darlington from damage due to load dump or other causes of excessive Vbat. Component Values Pickup Coil ­ series resistance 25°C inductance @ 1.0 kHz @ 15 Vrms leakage 0.6 mH primary R 25°C primary 5.0 A load resistor for pickup ± 20% input buffer resistors provide additional transient protection to the already clamped inputs C2 ­ for reduction of high frequency noise and spark transients induced in pick­up and leads; optional and non­critical provides load dump protection (but small enough to allow operation at Vbat 4.0 V) transient filter on VCC, non­critical stores reference, circuit designed for 20% RGain/RD1 sets the DC gain of the current regulator 20% RD2/RD1 set up voltage feedback from RS sense resistor (PdAg in thick film techniques) low enough to supply drive to the output Darlington, high enough to keep VCE(sat) of the IC below Darlington turn­on during load dump W starting with 35 assures less than 5.5 A, increasing as required to set 5.5 A

General Layout Notes The major concern in the substrate design should be to reduce ground resistance problems. The first area of concern is the metallization resistance in the power ground to module ground and the output to the Rdrive resistor. This resistance directly adds to the VCE(sat) of the IC power device and if not minimized could cause failure in load dump. The second concern is to reference the sense ground as close to the ground end of the sense resistor as possible in order to further remove the sensitivity of ignition coil current to ground I.R. drops. All versions were designed to provide the same pin­out order viewed from the top (component side) of the board or substrate. This was done to eliminate conductor cross­overs. The standard MC3334 plastic device is numbered in the industry convention, counter­clockwise viewed from the top, or bonding pad side. The MCCF3334 "flip" or "bump" chip is made from reversed artwork, it is numbered clockwise viewed from its bump side. Since this chip is mounted face down, the resulting assembly still has the same counter­clockwise order viewed from above the component surface. All chips have the same size and bonding pad spacing. See Figure 4 for dimensions.


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