ltm4608a Linear Technology Corporation, ltm4608a Datasheet - Page 15

• Manufacturer Part Number: ltm4608a
• Description: Low Vin, 8a Dc/dc ?module With Tracking, Margining, And Frequency Synchronization
• Manufacturer: Linear Technology Corporation

same as the slave regulator’s feedback divider to implement
coincident tracking. The LTM4608A uses an accurate 10k
resistor internally for the top feedback resistor. Figure 5
shows an example of coincident tracking:
V
pin. V
internal reference voltage. When the Master’s output is
divided down with the same resistor values used to set
the slave’s output, this resistor divider is connected to
the slave’s track pin. The slave will then coincident track
with the master until it reaches its fi nal value. The master
will continue to its fi nal value from the slave’s regulation
point. Voltage tracking is disabled when V
than 0.596V.
APPLICATIONS INFORMATION
TRACK
Slave = 1+
TRACK
is the track ramp applied to the slave’s track
has a control range of 0V to 0.596V, or the
R
10k
V
FB4
5V
IN
• V
OR APPLY AN EXTERNAL TRACKING RAMP
TRACK
t = –(ln (1 – 0.596/V
C
RAMP WITH R
SR
APPLY A CONTROL
100μs SOFT-START
R
TIED TO V
FOR DISABLE
AND DEFAULT
SR
TIE TO V
MASTER
Figure 5. Dual Outputs (3.3V and 1.5V) with Tracking
3.3V
IN
IN
R
10k
R
6.65k
IN
SR
C
) • R
FB3
FB4
WHERE
SR
AND
TRACK
SR
• C
RUN
RUN
TRACK
TRACK
SR
)
is more
V
SV
SW
RUN
PLLLPF
TRACK
MODE
PHMODE
V
SV
SW
RUN
PLLLPF
TRACK
MODE
PHMODE
CLKOUT GND
CLKOUT GND
IN
IN
IN
IN
LTM4608A
LTM4608A
CLKIN
CLKIN
The track pin of the master can be controlled by an external
ramp or by R
RC ramp time can be programmed using equation:
SGND
SGND
PGOOD
PGOOD
BSEL
BSEL
V
MGN
V
MGN
I
I
t = – ln 1–
THM
THM
OUT
OUT
I
I
FB
FB
TH
TH
4608A F05
Figure 6. Output Voltage Coincident Tracking
3.3V
1.5V
R
6.65k
R
2.21k
SR
FB2
FB1
C2
100pF
and C
0.596V
V
IN
C1
100μF
C3
22pF
SR
100μF
in Figure 5 referenced to V
+
• R
TIME
MASTER
3.3V
7A
C4
100μF
SR
MASTER OUTPUT
• C
SLAVE OUTPUT
SLAVE
1.5V
8A
SR
LTM4608A
4608A F06
15
IN
. The
4608af