DC1400A Linear Technology, DC1400A Datasheet - Page 15

• Manufacturer Part Number: DC1400A
• Description: BOARD EVAL LTM4608
• Manufacturer: Linear Technology
• Series: LTM®r

Specifications of DC1400A

• Main Purpose: DC/DC, Step Down
• Outputs And Type: 1, Non-Isolated
• Voltage - Output: 1.2V, 1.5V, 1.8V, 2.5V, 3.3V
• Current - Output: 8A
• Voltage - Input: 2.5 ~ 5.5 V
• Regulator Topology: Buck
• Frequency - Switching: 1.5MHz
• Board Type: Fully Populated
• Utilized Ic / Part: LTM4608
• Lead Free Status / RoHS Status: Not applicable / Not applicable
• Power - Output: -

CLKIN is tied to ground or if it’s driven by an external
frequency synchronization signal. A capacitor value of
0.01µF must be placed from the PLLLPF pin to ground to
control the slew rate of the spread spectrum frequency
change. Add a control ramp on the TRACK pin with R
and C
for spread spectrum operation.
Output Voltage Tracking
Output voltage tracking can be programmed externally
using the TRACK pin. The output can be tracked up and
down with another regulator. The master regulator’s output
is divided down with an external resistor divider that is the
APPLICATIONS INFORMATION
R
SR
SR
≥
referenced to V
− ln 1−






V
5V
IN
0.592
V
IN
OR APPLY AN EXTERNAL TRACKING RAMP
IN
1
t = –(ln (1 – 0.596/V

 • 500 • C

. Figure 21 shows an example
C
RAMP WITH R
SR
100µs SOFT-START
APPLY A CONTROL
R
TIED TO V
AND DEFAULT
FOR DISABLE
SR
TIE TO V
MASTER
Figure 5. Dual Outputs (3.3V and 1.5V) with Tracking
3.3V
SR
IN
IN
R
10k
R
6.65k
IN
SR
C
) • R



FB3
FB4
WHERE
SR
AND
SR
• C
RUN
RUN
TRACK
TRACK
SR
)
V
SV
SW
RUN
PLLLPF
TRACK
MODE
PHMODE
V
SV
SW
RUN
PLLLPF
TRACK
MODE
PHMODE
CLKOUT GND
CLKOUT GND
IN
IN
IN
IN
SR
LTM4608A
LTM4608A
CLKIN
CLKIN
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
V
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 final value. The master will continue to
its final value from the slave’s regulation point. Voltage
tracking is disabled when V
SGND
SGND
PGOOD
PGOOD
TRACK
TRACK
BSEL
BSEL
V
MGN
V
MGN
I
I
Slave = 1+
THM
THM
OUT
OUT
I
I
FB
FB
TH
TH
has a control range of 0V to 0.596V, or the internal
is the track ramp applied to the slave’s track pin.



R
6.65k
R
2.21k
FB1
FB2
C2
100pF
R
10k
FB4
C1
100µF
C3
22pF

 • V

100µF
V
+
IN
TRACK
50k
50k
TRACK
C4
100µF
4608A F05
is more than 0.596V.
LTM4608A
MASTER
3.3V
7A
SLAVE
1.5V
8A
15
4608afc