Preliminary Data Sheet

TDA21201

Page 7

Apr-29, 2002

being fully On at a VCC level slightly greater than the threshold.

Bootstrapping

Turning on and off the High side MOSFET is done internally by the Driver. The

TDA21201 does not require any external bootstrap components such as a

capacitor or diode. Just apply GND, Vcc = 12 V, and the PWM signal of the

Controller to it and the Integrated Switch will operate.

Input filter / Output filter / Converter Stability

The Integrated Switch TDA21201 is a new solution to implement the power

semiconductor components in a DC/DC converter. It offers many advantages

to the user. However, the basic behavior with respect to the voltages, the

currents and the timing remains unchanged. Therefore, any of the rules and

procedures applied to design DC/DC converters using discrete MOSFETs and

Drivers apply in the same way to converters using the Integrated Switch –

except the worries regarding dead time control, lowest impedance in the AC

loop, elevated driver temperatures etc.

Current sense

Any of the commonly used current sense techniques are supported by the

Integrated Switch. For Low side sensing measure the voltage drop across the

GND pins and the OUT pin (or the tab when using the SMD version) during

the Low side switch’s On-time (Vin = Low). The High side MOSFET is sensed

across the Vcc and the OUT pin (or the tab when using the SMD version) of

the Integrated Switch during its On-time (Vin = High). Inductor sensing is

implemented outside of the integrated switch the usual way.

Resistor sensing using a separate resistor in the Input capacitor

à High side

MOSFET (Vcc pin) path is possible but not recommended. This current sense

approach introduces ample stray inductance in the AC current loop (+terminal

of the input capacitor

à High side MOSFET à Low side MOSFET à GND à

-terminal of the input capacitor). This results in a very noisy Vcc line especially

during the switching period and a non-optimized switching behavior of the

Integrated Switch. This in turn, increases the switching losses and the device

temperature and lowers the efficiency.

Output current scalability

The converter output current can be chosen in a wide range by selecting the

appropriate number of phases. At a given number of phases the current per

phase (= current per TDA21201) and in turn the overall converter output

current is set by application requirements, e.g. the switching frequency, and by

environmental conditions, e.g. ambient temperature and the thermal

resistance of the TDA21201 to ambient. As a reference, one TDA21201

This amount of loss can be dissipated by the SMD version of the Integrated

Switch on a regular motherboard using proper thermal design techniques.

Greater phase currents result in higher losses; and higher switching