A5975ADTR STMicroelectronics, A5975ADTR Datasheet - Page 16
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A5975ADTR
Manufacturer Part Number
A5975ADTR
Description
IC REG SW STEP-DOWN 2.5A 8SOIC
Manufacturer
STMicroelectronics
Series
-r
Type
Step-Down (Buck), PWMr
Datasheet
1.A5975ADTR.pdf
(50 pages)
Specifications of A5975ADTR
Internal Switch(s)
Yes
Synchronous Rectifier
No
Number Of Outputs
1
Voltage - Output
1.235 V ~ 35 V
Current - Output
2.5A
Frequency - Switching
500kHz
Voltage - Input
4 V ~ 36 V
Operating Temperature
-40°C ~ 125°C
Mounting Type
Surface Mount
Package / Case
8-SOIC (0.154", 3.90mm Width) Exposed Pad
Lead Free Status / Rohs Status
Lead free / RoHS Compliant
Other names
497-11425-2
Available stocks
Company
Part Number
Manufacturer
Quantity
Price
Part Number:
A5975ADTR
Manufacturer:
ST
Quantity:
20 000
Functional description
5.6
16/50
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 the 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.
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 numerous problems:
The fall time of the current during turn-off is also critical, as it produces voltage spikes (due
to the parasitic 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
free-wheeling diode recovery time problem. The gate clamp is necessary to ensure that V
of the internal switch does not go higher than V
against any cross conduction between the supply line and ground.
Spikes on the device supply voltage that cause oscillations (and therefore noise) due to
the board parasites.
Turn-on overcurrent leads to a decrease in the efficiency and system reliability.
Major EMI problems.
Shorter free-wheeling diode life.
Figure
Doc ID 018761 Rev 1
8. The basic idea is to change the current levels used to
GS
max. The on/off control block protects
A5975AD
GS