LTM4606(RevB) View Datasheet(PDF) - Linear Technology
Part Name
Description
MFG CO.
LTM4606 Datasheet PDF : 28 Pages
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LTM4606
Applications Information
Output Voltage Tracking
Output voltage tracking can be programmed externally
using the TRACK/SS pin. The output can be tracked up and
down with another regulator. Figure 4 shows an example
of coincident tracking where the master regulator’s output
is divided down with an external resistor divider that is the
same as the slave regulator’s feedback divider. Ratiometric
modes of tracking can be achieved by selecting different
resistor values to change the output tracking ratio. The
master output must be greater than the slave output for
the tracking to work. Figure 5 shows the coincident output
tracking characteristics.
VIN
CIN
MASTER
OUTPUT
TRACK
CONTROL
R2
60.4k
R1
19.1k
100k
VD
VIN PLLIN
PGOOD
RUN LTM4606
COMP
VOUT
VFB
FCB
INTVCC
DRVCC
fSET
TRACK/SS
SGND
MARG0
MARG1
MPGM
PGND
SLAVE
OUTPUT
COUT 2.5V
19.1k
4606 F04
Figure 4. Output Voltage Coincident Tracking
OUTPUT
VOLTAGE
MASTER OUTPUT
SLAVE OUTPUT
Run Enable
The RUN pin is used to enable the power module. The
pin has an internal 5.1V zener to ground. The pin can be
driven with a logic input not to exceed 5V.
The RUN pin can also be used as an undervoltage lock out
(UVLO) function by connecting a resistor divider from the
input supply to the RUN pin:
VUVLO
=
R1+ R2
R2
•
1.5V
where R2 is the bottom resistor of the divider, R1 is the
top resistor of the divider.
Power Good
The PGOOD pin is an open-drain pin that can be used to
monitor valid output voltage regulation. This pin monitors
a ±10% window around the regulation point and tracks
with margining.
COMP Pin
This pin is the external compensation pin. The module
has already been internally compensated for most output
voltages. Table 2 is provided for most application require-
ments. LTpowerCAD™ is available for other control loop
optimization.
FCB Pin
The FCB pin determines whether the bottom MOSFET
remains on when current reverses in the inductor. Tying
this pin above its 0.6V threshold enables discontinuous
operation where the bottom MOSFET turns off when in-
ductor current reverses. FCB pin below the 0.6V threshold
forces continuous synchronous operation, allowing current
to reverse at light loads and maintain low output ripple.
TIME
4606 F05
Figure 5. Coincident Tracking Characteristics
4606fb
14
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