EVALA5972D STMicroelectronics, EVALA5972D Datasheet - Page 9

• Manufacturer Part Number: EVALA5972D
• Description: Power Management Modules & Development Tools EVAL BOARD A5972 Auto Grade
• Manufacturer: STMicroelectronics
• Type: DC/DC Switching Converters, Regulators & Controllersr

Specifications of EVALA5972D

• Input Voltage: 4.4 V to 36 V
• Output Voltage: 1.235 V to 35 V
• Board Size: 23 mm x 20 mm
• Product: Power Management Modules
• Supply Current: 2 A
• Dimensions: 23 mm x 20 mm
• For Use With/related Products: AN1517
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

AN1517
2.7
the faster the rise time, the lower the turn ON losses. However, there is a limit introduced by
the recovery time of the recirculation diode.
In fact, when the current of the power element is equal to the inductor current, the diode
turns OFF and the drain of the power is able to go high. But during its recovery time, the
diode can be considered a high value capacitor and this produces a very high peak current,
responsible for many problems:
●
●
●
●
The fall time of the current during the turn OFF is also critical, as it produces voltage spikes
(due to the parasitics elements of the board) that increase the voltage drop across the
PDMOS.
In order to minimize these problems, a new driving circuit topology has been used and the
block diagram is shown in
turn the power switch ON and OFF, based on the PDMOS and the gate clamp status.
This circuitry allows the power switch to be turned OFF and ON quickly and addresses the
freewheeling diode recovery time problem. The gate clamp is necessary to avoid that V
the internal switch goes higher than V
any cross conduction between the supply line and ground.
Figure 8.
Thermal shutdown
The Thermal Shutdown block generates a signal that turns OFF the power stage if the
temperature of the chip goes higher than a fixed internal threshold (150 °C). The sensing
element of the chip is very close to the PDMOS area, ensuring fast and accurate
temperature detection. A hysteresis of approximately 20 °C avoids that the device turns ON
and OFF continuously.
Spikes on the device supply voltage that cause oscillations (and thus noise) due to the
board parasitics
Turn ON over-current leads to a decrease in the efficiency and system reliability
Major EMI problems
Shorter freewheeling diode life
Driving circuitry
DRIVE
DRAIN
STOP
Vgs max
Figure
CONTROL
ON/OFF
CLAMP
8. The basic idea is to change the current levels used to
GATE
GS
OFF
ON
max. The ON/OFF Control block protects against
DRAIN
I
I
OFF
ON
VCC
PDMOS
L
ESR
C
AM00009v1
VOUT
Functional description
I
LOAD
GS
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