High Current Output drivers
Posted: Tue Sep 23, 2008 2:33 pm
I have been thinking about this for a while and thought I'd post a bit more about high current drivers. I was reviewing the Saab Trionic ECU (Moto 332 based) for algorithm type information and caught this. For all high current outputs, they use MTD3055VL http://www.fairchildsemi.com/ds/MT/MTD3055VL.pdf. Note that these are 12A devices. These are used for each injector as well as other solenoids, etc. My concern with smaller (5A) devices on the injectors is that low PW injector control may compromised. I know that higher current devices can be swapped in at any time, but thought I'd post this as a note. It'd be interesting to see if there is any difference in PW control accuracy with a stiffer FET driving the injector.
As a side note, it is interesting that they also use a LM1815 for the crank sensor conditioning. For the low level COP ignition outputs, they use a quad 700ma NPN driver (CA3262). all analog inputs go through a TLC546, 8 bit a/d converter and are fed in serial to the 332! This takes in: TPS, MAP, BattV, IAT, CLT, O2 and Knock. All 8 bit all serially in to the 20 MHz 332!!! This is for a very sophisticated adaptive engine management system.
Another note is the voltage regulator (2 channel):
Just thought I'd share.
Gearhead
As a side note, it is interesting that they also use a LM1815 for the crank sensor conditioning. For the low level COP ignition outputs, they use a quad 700ma NPN driver (CA3262). all analog inputs go through a TLC546, 8 bit a/d converter and are fed in serial to the 332! This takes in: TPS, MAP, BattV, IAT, CLT, O2 and Knock. All 8 bit all serially in to the 20 MHz 332!!! This is for a very sophisticated adaptive engine management system.
Another note is the voltage regulator (2 channel):
Also of interest is that Saab uses lambda adaptation to accommodate for altitude (baro correction)Power supply
The board is power by the car battery. The input voltage (+11V - +14V) is transformed to a usable
voltage by the L4937 (Voltage regulator). The input voltage (from the battery) is supplied to
pin number 1 on the regulator. The output voltages (Vo1 and Vo2) are stabilized +5 volt which can
sink 50 mA and 500 mA respectively. The Vo1 is a standby voltage. If the ignition is turned off an RC
network will keep the power supply in operational state for a while and then lets it resume into
standby mode in which the power drain is significantly lower. The maximum standby current the
regulator can sink is 50 mA. Nice to know is that the regulator can supply its +5 volt output when the
input ranges from +6V up to +28V (with transient spikes up to +40V).
Just thought I'd share.
Gearhead