EVALA5970AD STMicroelectronics, EVALA5970AD Datasheet - Page 12

• Manufacturer Part Number: EVALA5970AD
• Description: BOARD EVAL FOR A5970AD REG
• Manufacturer: STMicroelectronics

Specifications of EVALA5970AD

• Main Purpose: DC/DC, Step Down
• Outputs And Type: 1, Non-Isolated
• Voltage - Output: 1.235 ~ 35V
• Current - Output: 1A
• Voltage - Input: 4 ~ 36V
• Regulator Topology: Buck
• Frequency - Switching: 500kHz
• Board Type: Fully Populated
• Utilized Ic / Part: A5970AD
• Product: Power Management Modules
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Power - Output: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

Functional description
5.5
5.6
12/42
threshold. The frequency shifter
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 5.
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.
However, there is a limit introduced by the recovery time of the recirculation diode.
Transconductance
Low frequency gain
Minimum sink/source voltage
Output voltage swing
Input bias current
Description
Current limitation circuitry
Uncompensated error amplifier characteristics
Doc ID 14661 Rev 4
(Figure
5) functions based on the feedback voltage. As the
1500 µA/300 µA
0.4 V/3.65 V
2300 µS
Values
2.5 µA
65 dB
A5970AD