I need to power a mobile communications module (2G/3.5G GSM/HSPA) from an automotive 24V power rail. That means nominal 10V to 32V Vin range, and the converter should go higher to allow for operation during transient at the clamping voltage of the input protection. The module is powered at 3.8V DC nominal and in GSM mode it will consume current in up to 2A pulses when transmitting with 1/8 duty cycle.
The manufacturer also gives specifications for allowable ripple and at each frequency band on the DC suplly rail and voltage drop, and it tells you that if you use a switching regulator it needs to switch at above 600 kHz or else they can't guarantee compliance.
I'm constrained in PCB area and the design should be low-ish cost. The problem is that the requirements are contradictory. Most regulators capable of the required Vin range won't work because the application requires too low Ton for the switch, and out of those claiming that they can do the job because they use topologies optimized for this, most come from manufacurers like allegro that don't provide data on ripple/transient reponse nor any simulation model nor any way to evaluate how they work apart from buying the eval board and tinkering with it.
So, due to the lack of options availabe for the job I thought about cascading switching regulators to reduce Vin to Vout in two stages and allow for more relaxed duty cycle and Ton requirements but the area constrainment makes me not like this option due to extra space required for two converters, and I've also never cascaded two switchmode regulators operating at similar frequencies and for what I've read it's not that immediate to assess the performance of both of them working in this configuration.
Could you recommend me a topology for this application?