LTC3890EGN-1#TRPBF Linear Technology, LTC3890EGN-1#TRPBF Datasheet - Page 15

• Manufacturer Part Number: LTC3890EGN-1#TRPBF
• Description: IC BUCK SYNC ADJ DUAL 28SSOP
• Manufacturer: Linear Technology
• Type: Step-Down (Buck)r

Specifications of LTC3890EGN-1#TRPBF

• Internal Switch(s): No
• Synchronous Rectifier: Yes
• Number Of Outputs: 2
• Voltage - Output: 0.8 ~ 24 V
• Frequency - Switching: 350kHz ~ 535kHz
• Voltage - Input: 4 ~ 60 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 28-SSOP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Current - Output: -
• Power - Output: -

The Typical Application on the first page is a basic
LTC3890-1 application circuit. LTC3890-1 can be configured
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 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
R
power MOSFETs and Schottky diodes are selected. Finally,
input and output capacitors are selected.
SENSE
The SENSE
comparators. The common mode voltage range on these
pins is 0V to 28V (abs max), enabling the LTC3890-1 to
regulate output voltages up to a nominal 24V (allowing
margin for tolerances and transients).
The SENSE
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
the common mode voltage. When SENSE
INTV
of the pin. When SENSE
current (~700μA) flows into the pin. Between INTV
0.5V and INTV
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
APPLICATIONS INFORMATION
SENSE
CC
+
– 0.5V, a small current of less than 1μA flows out
(if R
and SENSE
+
+
SENSE
and SENSE
pin is high impedance over the full common
CC
+ 0.5V, the current transitions from the
is used) and inductor value. Next, the
–
Pins
–
–
pins are the inputs to the current
is above INTV
–
pin changes depending on
CC
+ 0.5V, a higher
–
is less than
CC
–
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.
Figure 3. Sense Lines Placement with Inductor or Sense Resistor
*PLACE C1 NEAR
SENSE PINS
LTC3890-1
LTC3890-1
SENSE
SENSE
SENSE
SENSE
INTV
BOOST
INTV
BOOST
SGND
SGND
(4b) Using the Inductor DCR to Sense Current
SW
V
SW
BG
V
TG
BG
CC
TG
IN
CC
IN
+
–
+
–
(4a) Using a Resistor to Sense Current
Figure 4. Current Sensing Methods
*R1 AND C1 ARE OPTIONAL.
(R1 || R2) C1 =
NEXT TO THE CONTROLLER
C1*
C1*
INDUCTOR OR R
TO SENSE FILTER,
R1*
PLACE CAPACITOR NEAR
SENSE PINS
R2
R1
DCR
L
R
SENSE
SENSE(EQ)
38901 F03
V
V
LTC3890-1
INDUCTOR
R
IN
IN
L
SENSE
= DCR
C
OUT
DCR
R1 + R2
R2
38901 F04a
V
OUT
15
38901 F04b
38901fa
V
OUT