AST1S31HF datasheet(12/33 Pages) STMICROELECTRONICS

12 / 33 page

Functional description

AST1S31HF

12/33

DocID026968 Rev 2

Figure 5. Block diagram of the loop for the small signal analysis

Three main terms can be identified to obtain the loop transfer function:

From control (output of E/A) to output, GCO(s)

From output (Vout) to the FB pin, GDIV(s)

From the FB pin to control (output of E/A), GEA(s).

The transfer function from control to output GCO(s) results:

Equation 2

where RLOAD represents the load resistance, Ri the equivalent sensing resistor of the

current sense circuitry (0.38

),

p the single pole introduced by the LC filter and z the

zero given by the ESR of the output capacitor.

FH(s) accounts the sampling effect performed by the PWM comparator on the output of the

error amplifier that introduces a double pole at one half of the switching frequency.

Equation 3

Cout

Current sense

Logic

And

Driver

Slope

Compensation

PWM comparator

Error Amp

0.8V

High side

Switch

Low side

Switch

GCO(s)

GDIV(s)

GEA(s)

VIN

VOUT

VFB

GCO s



RLOAD

------------------

Rout TSW



----------------------------

mC 1D

–

 0.5

–







---------------------------------------------------------------------------------------------



------







------





---------------------- FH s









ESR COUT



-------------------------------

AST1S31HF bảng dữ liệu(PDF) 12 Page - STMicroelectronics

AST1S31HF bảng dữ liệu(HTML) 12 Page - STMicroelectronics

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33

bảng dữ liệu tải về

Link URL