LTC3370 datasheet(23/44 Pages) LINER

23 / 44 page

LTC3372

Rev. A

For more information www.analog.com

HIGH VOLTAGE BUCK CONTROLLER

The Typical Application on the first page is a basic applica-

tioncircuit.TheHVcontrollerinductorcurrentsensingcan

be configured to use either DCR (inductor resistance) or a

low value sense resistor. The choice between the two cur-

rentsensingschemesislargelyadesigntrade-offbetween

cost, power consumption and accuracy. DCR sensing

has become popular because it saves expensive current

sensing resistors and is more power efficient, especially

in high current applications. However, current sensing

resistors provide the most accurate current limits for the

controller. Other external component selection is driven

by the load requirement, and begins with the selection of

RSENSE (if RSENSE is used) and inductor value. Next, the

power MOSFETs. Finally, input and output capacitors are

selected.

Current Sense Pins (SENSE+ and SENSE–)

The SENSE+ and SENSE– pins are the inputs to the cur-

rent comparators. The common mode voltage range on

these pins is 0V to 6V (abs max), allowing margin for

tolerances and transients for the HV regulator’s regulated

5V or 3.3V output.

The SENSE+ pin is high impedance over the full common

mode range, drawing at most ±1μA. This high impedance

allows the current comparators to be used in inductor

DCR sensing.

Connect the SENSE– pin directly to the sense point at the

VOUT side of the inductor (in DCR sensing) or the current

sense resistor (RSENSE), without adding any resistor in se-

ries.TheimpedanceoftheSENSE–pinchangesdepending

on its voltage. When SENSE– is less than INTVCC – 0.5V,

a small current of less than 1μA flows out of the pin. As

SENSE–approachesINTVCC,thecurrenttransitionshigher

to close to 1mA.

Filter components mutual to the sense lines should be

placed close to the IC, and the sense lines should run

close together to a Kelvin connection underneath the

current sense element (shown in Figure 2). Sensing cur-

rent elsewhere can effectively add parasitic inductance

and capacitance to the current sense element, degrading

the information at the sense terminals and making the

programmed current limit unpredictable. If inductor DCR

sensing is used (Figure 3b), resistor R1 should be placed

closetotheswitchingnode,topreventnoisefromcoupling

into sensitive small-signal nodes.

APPLICATIONS INFORMATION

COUT

TO SENSE FILTER,

NEXT TO THE CONTROLLER

INDUCTOR OR RSENSE

3372 F02

VIN

RSENSE

INTVCC

BOOST

PLACE CAPACITOR NEAR

SENSE PINS

SENSE+

SENSE–

GND

LTC3372

VOUT

3372 F03a

*R1 AND C1 ARE OPTIONAL

C1*

R1*

VIN

INTVCC

BOOST

*PLACE C1 NEAR

SENSE PINS

INDUCTOR

DCR

SENSE+

SENSE–

GND

LTC3372

VOUT

3372 F03b

C1*

(R1||R2) • C1 = L

DCR

RSENSE(EQ) = DCR

R1 + R2

Figure 2. Sense Lines Placement with Inductor or Sense Resistor

Figure 3. Current Sensing Methods

(3a) Using a Resistor to Sense Current

(3b) Using the Inductor DCR to Sense Current

High Voltage Buck Controller

LTC3370 датащи(PDF) 23 Page - Linear Technology

LTC3370 датащи(HTML) 23 Page - Linear Technology

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 34 35 36 37 38 39 40 41 42 43 44

датащи скачать

ссылки URL