LTC3856EFE#TRPBF Linear Technology, LTC3856EFE#TRPBF Datasheet - Page 25

• Manufacturer Part Number: LTC3856EFE#TRPBF
• Description: IC REG CTLR 2CHAN SYNC 38TSSOP
• Manufacturer: Linear Technology
• Type: Step-Down (Buck)r

Specifications of LTC3856EFE#TRPBF

• Internal Switch(s): No
• Synchronous Rectifier: Yes
• Number Of Outputs: 1
• Voltage - Output: 0.6 ~ 5 V
• Frequency - Switching: 250kHz ~ 770kHz
• Voltage - Input: 4.5 ~ 38 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 38-TSSOP Exposed Pad, 38-eTSSOP, 38-HTSSOP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Current - Output: -
• Power - Output: -

applicaTions inForMaTion
error amplifier. The amplifier has an output swing range
of 0V to 3.6V. The output uses an NPN emitter follower
with 80k feedback resistance.
Active Voltage Positioning (AVP)
In an application, the AVP scheme modifies the regulated
output voltage depending on its current loading. AVP
can improve overall transient response and save power
consumption.
The LTC3856 senses inductor current information by moni-
toring voltage drops across the sense resistors R
the DCR sensing network of the two channels. The voltage
drops are added together and applied as V
the AVP and DIFFP pins, which are connected through
resistor R
and added to output voltage as the compensation for the
load voltage drop.
Let:
then:
The final load slope is defined by the inductor current
sense resistors and the two external resistors previously
mentioned.
In summary, the load slope is:
The recommended value for R
maximum output voltage at AVP is 2.5V. Therefore, for
outputs higher than 2.5V, the AVP function is not supported.
The DIFFP pin, however, should always be connected to the
output even when AVP or diffamp functions are not used.
∆V = V
∆V = V

 
∆
R
V
DIFFP VOUT
SENSE
SENSE1
SENSE2
PRE-AVP
,
•
R
PRE-AVP
R
+
+
=
. Then V
AVP
– V
– V
2
•
SENSE1
SENSE2
∆
V

 



V A
PRE-AVP
R
/
–
–
PRE-AVP
R
AVP
AVP
is scaled through R
is 90Ω to 100Ω. The



PRE-AVP
between
SENSE
AVP
or
Programmable Stage Shedding Mode
When the MODE pin is tied to INTV
ters Stage Shedding mode. This means that the second
channel will stop switching when I
programmed threshold. This threshold voltage on I
programmed according to the following formula:
The valid range of V
is the voltage on the ISET pin. There is a precision 7.5µA
flowing out of the ISET pin. Connecting a resistor to SGND
sets the V
be at INTV
in this case will be 0.5V. There is a 50mV hysteresis for
the Stage Shedding mode threshold comparator.
Programmable Burst Mode Operation
When the MODE pin is floating, the LTC3856 enters Burst
Mode operation. This means that both channels will stop
switching when I
The Burst Mode clamp, which sets the current limit when
bursting, can be programmed through V
the following formula:
The valid range of V
V
7.5µA flowing out of ISET. Connecting a resistor to SGND
sets the V
INTV
be 0.7V. There is a 50mV hysteresis for the Burst Mode
comparator.
ISET
V
V
CLAMP
SHED
CC
is the voltage on the ISET pin. There is a precision
. The Burst Mode clamp voltage in this case will
ISET
CC
ISET
=
= 0.7 + 0.62 (0.5 – V
. The Stage Shedding mode threshold voltage
0 5
voltage. When left floating, V
.
voltage. When left floating, V
+
TH

 
ISET
is below a certain threshold.
5
3
ISET

 
is between 0V to 0.5V, where V
•
(
0 5
is between 0.3V to 0.5V and
.
−
ISET
V
ISET
TH
)
CC
)
, the LTC3856 en-
is below a certain
LTC3856
ISET
ISET
ISET
according to
voltage will
will be at

TH
ISET
3856f
is