EVALA5973AD STMicroelectronics, EVALA5973AD Datasheet - Page 8

• Manufacturer Part Number: EVALA5973AD
• Description: Power Management Modules & Development Tools EVAL BOARD A5973AD Auto Grade
• Manufacturer: STMicroelectronics
• Type: DC/DC Switching Converters, Regulators & Controllersr

Specifications of EVALA5973AD

• 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: 2.5 A
• Dimensions: 23 mm x 20 mm
• For Use With/related Products: AN1518
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Functional description
3.5
3.6
8/30
again. For this reason the switching frequency is also reduced, thus keeping the inductor
current under its maximum threshold. The Frequency Shifter
the feedback voltage. As the feedback voltage decreases (due to the reduced duty cycle),
the switching frequency decreases also.
Figure 7.
Error amplifier
The voltage error amplifier is the core of the loop regulation. It is a transconductance
operational amplifier whose non inverting input is connected to the internal voltage
reference (1.235 V), while the inverting input (FB) is connected to the external divider or
directly to the output voltage. The output (COMP) is connected to the external compensation
network. The uncompensated error amplifier has the following characteristics:
Table 2.
The error amplifier output is compared to the oscillator sawtooth to perform PWM control.
PWM comparator and power stage
This block compares the oscillator sawtooth and the error amplifier output signals to
generate the PWM signal for the driving stage.
The power stage is a highly critical block, as it functions to guarantee a correct turn ON and
turn OFF of the PDMOS. The turn ON of the power element, or more accurately, the rise
time of the current at turn ON, is a very critical parameter. At a first approach, it appears that
the faster the rise time, the lower the turn ON losses.
Transconductance
Low frequency gain
Minimum sink/source voltage
Output voltage swing
Input bias current
Description
Current limitation circuitry
Uncompensated error amplifier characteristics
1500 µA/300 µA
0.4 V/3.65 V
2300 µS
Values
2.5 µA
65dB
(Figure
6) functions based on
AN1518