Datasheet

LTC3883/LTC3883-1
21
3883fa
For more information www.linear.com/LTC3883
Figure 3. Load Sharing Connections for 2-Phase Operation
OPERATION
command. The resulting measured powerstage current
is returned by the READ_IIN command.
The MFR_READ_IIN_CHAN command returns the
calculated powerstage current based on the READ_IOUT
value multiplied by the READ_DUTY_CYCLE value.
The LTC3883 uses an internal 1Ω sense resistor to
measure the V
IN
pin supply current being consumed by the
LTC3883. This value is returned by the MFR_READ_ICHIP
command. Refer to the subsection titled Input Current
Sense Amplifier in the Applications Information section
for further detail.
LOAD SHARING
Multiple LTC3883’s can be arrayed in order to provide a
balanced load-share solution by bussing the necessary
pins. Figure 3 illustrates the shared connections required
for load sharing.
The frequency must only be programmed on one of the
LTC3883s. The other(s) must be programmed to External
Clock.
EXTERNAL/INTERNAL TEMPERATURE SENSE
External temperature can be best measured using a remote
diode-connected PNP transistor such as the MMBT3906.
The emitter should be connected to the TSNS pin while the
base and collector terminals of the PNP transistor should
be returned to the LTC3883’s GND pin, preferably using a
star connection. It is possible
to connect
the collector of the
PNP to the source of the bottom MOSFET. This may optimize
board layout allowing the PNP closer proximity to the power
FETs. The base of the PNP must still be tied to ground. For
best noise immunity, the connections should be routed
differentially and a 10nF capacitor should be placed in parallel
with the diode connected PNP. Two different currents are
applied to the diode (nominally 2µA and 32µA) and the
100Ω 100Ω
100Ω 100Ω
LTC3883 + POWER STAGE
I
TH
V
IN
POWER STAGE
I
IN_SNS
V
IN_SNS
LTC3883 + POWER STAGE
I
TH
NOTE: SOME CONNECTORS
AND COMPONENTS OMITTED
FOR CLARITY
I
SENSE
+
I
SENSE
–
V
SENSE
+
V
SENSE
–
CONTROL
V
SUPPLY
SMBALERT
FAULT
PWM CLOCK
SHARE CLOCK
RUN
ALERT
GPIO
SYNC
SHARE_CLK
RUN
ALERT
GPIO
SYNC
SHARE_CLK
I
SENSE
+
I
SENSE
–
PGNDGND
PGND
3883 F03
GND
V
SENSE
+
V
SENSE
–
LOAD
I
IN_SNS
V
IN_SNS
V
IN
POWER STAGE