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参数资料
| 型号： | LTC3890EGN-1#PBF |
| 厂商： | LINEAR TECHNOLOGY CORP |
| 元件分类： | 稳压器 |
| 英文描述： | SWITCHING CONTROLLER, PDSO28 |
| 封装： | LEAD FREE, PLASTIC, SSOP-28 |
| 文件页数： | 7/36页 |
| 文件大小： | 498K |
| 代理商： | LTC3890EGN-1#PBF |
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LTC3890-1
15
38901f
APPLICATIONS INFORMATION
Figure 3. Sense Lines Placement with Inductor or Sense Resistor
(4a) Using a Resistor to Sense Current
(4b) Using the Inductor DCR to Sense Current
Figure 4. Current Sensing Methods
The Typical Application on the rst page is a basic
LTC3890-1 application circuit. LTC3890-1 can be cong-
ured to use either DCR (inductor resistance) sensing or low
value resistor sensing. The choice between the two current
sensing schemes is largely a design trade-off between
cost, power consumption, and accuracy. DCR sensing
is becoming popular because it saves expensive current
sensing resistors and is more power efcient, 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 and Schottky diodes are selected. Finally,
input and output capacitors are selected.
SENSE+ and SENSE– Pins
The SENSE+ and SENSE– pins are the inputs to the cur-
rent comparators. The common mode voltage range on
these pins is 0V to 28V (abs max), enabling the LTC3857
to regulate output voltages up to a nominal 24V (allowing
margin for tolerances and transients).
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.
The impedance of the SENSE– pin changes depending on
the common mode voltage. When SENSE– is less than
INTVCC – 0.5V, a small current of less than 1μA ows out
of the pin. When SENSE– is above INTVCC + 0.5V, a higher
current (~700μA) ows into the pin. Between INTVCC
– 0.5V and INTVCC + 0.5V, the current transitions from
the smaller current to the higher current.
Filter components mutual to the sense lines should be
placed close to the LTC3890-1, and the sense lines should
run close together to a Kelvin connection underneath the
current sense element (shown in Figure 3). 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 4b), sense resistor R1 should be
placed close to the switching node, to prevent noise from
coupling into sensitive small-signal nodes.
COUT
TO SENSE FILTER,
NEXT TO THE CONTROLLER
INDUCTOR OR RSENSE
38901 F03
VIN
INTVCC
BOOST
TG
SW
BG
PLACE CAPACITOR NEAR
SENSE PINS
SENSE+
SENSE–
SGND
LTC3890-1
VOUT
RSENSE
38901 F04a
VIN
INTVCC
BOOST
TG
SW
BG
*PLACE C1 NEAR
SENSE PINS
INDUCTOR
DCR
L
SENSE+
SENSE–
SGND
LTC3890-1
VOUT
38901 F04b
R1
R2
C1*
(R1||R2) C1 =
L
DCR
RSENSE(EQ) = DCR
R2
R1 + R2
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| LTC3890EGN-3#PBF | 制造商:Linear Technology 功能描述:IC REG CTRLR BUCK PWM CM 28SSOP 制造商:Linear Technology 功能描述:DC-DC CONTROLLER BUCK 900KHZ 制造商:Linear Technology 功能描述:DC-DC CONTROLLER, BUCK, 900KHZ, SSOP-28 制造商:Linear Technology 功能描述:DC-DC CONTROLLER, BUCK, 900KHZ, SSOP-28; Primary Input Voltage:60V; No. of Outputs:2; No. of Pins:28; Operating Temperature Min:-40C; Operating Temperature Max:125C; Operating Temperature Range:-40C to +125C ;RoHS Compliant: Yes |
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