DC1400A Linear Technology, DC1400A Datasheet - Page 13

• 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: -

APPLICATIONS INFORMATION
provide more output current without increasing input and
output voltage ripple. The CLKIN pin allows the LTM4608A
to synchronize to an external clock (between 0.75MHz
and 2.25MHz) and the internal phase locked loop allows
the LTM4608A to lock onto CLKIN’s phase as well. The
CLKOUT signal can be connected to the CLKIN pin of the
following LTM4608A stage to line up both the frequency
and the phase of the entire system. Tying the PHMODE
pin to SV
difference (between CLKIN and CLKOUT) of 180°, 120°
or 90° respectively, which corresponds to a 2-phase,
3-phase or 4-phase operation. A total of 6 phases can be
cascaded to run simultaneously with respect to each other
by programming the PHMODE pin of each LTM4608A to
different levels. For a 6-phase example in Figure 2, the
2nd stage that is 120° out of phase from the 1st stage
can generate a 240° (PHMODE = 0) CLKOUT signal for
V
+
LTC6908-2
IN
OUT1
OUT2
CLKIN
PHMODE
, SGND or SV
PHASE 1
0
CLKOUT
CLKIN
PHMODE
CLKIN
PHMODE
+120
PHASE 1
PHASE 4
IN
90
0
CLKOUT
CLKOUT
/2 (floating) generates a phase
CLKIN
PHMODE
PHASE 3
120
+120
+120
CLKOUT
CLKIN
PHMODE
CLKIN
PHMODE
+120
S
PHASE 5
PHASE 8
VIN
120
210
CLKOUT
CLKOUT
CLKIN
PHMODE
Figure 3. 12-Phase Operation
Figure 2. 6-Phase Operation
PHASE 5
S
S
+120
+120
240
VIN
VIN
CLKOUT
CLKIN
PHMODE
CLKIN
PHMODE
PHASE 12
PHASE 9
+180
240
330
CLKOUT
CLKOUT
the 3rd stage, which then can generate a CLKOUT signal
that’s 420°, or 60° (PHMODE = SV
With the 60° CLKIN input, the next two stages can shift
120° (PHMODE = 0) for each to generate a 300° signal
for the 6th stage. Finally, the signal with a 60° phase shift
on the 6th stage (PHMODE is floating) goes back to the
1st stage. Figure 3 shows the configuration for 12-phase
operation.
A multiphase power supply significantly reduces the
amount of ripple current in both the input and output
capacitors. The RMS input ripple current is reduced by,
and the effective ripple frequency is multiplied by, the
number of phases used (assuming that the input voltage
is greater than the number of phases used times the output
voltage). The output ripple amplitude is also reduced by
the number of phases used.
CLKIN
PHMODE
PHASE 2
+180
+180
(420)
60
CLKOUT
CLKIN
PHMODE
CLKIN
PHMODE
PHASE 3
PHASE 6
(420)
(510)
+120
150
60
CLKOUT
CLKOUT
CLKIN
PHMODE
+120
+120
PHASE 4
180
CLKOUT
CLKIN
PHMODE
CLKIN
PHMODE
PHASE 10
PHASE 7
180
270
+120
CLKOUT
CLKOUT
LTM4608A
IN
CLKIN
PHMODE
) for the 4th stage.
+120
+120
PHASE 6
300
CLKOUT
CLKIN
PHMODE
CLKIN
PHMODE
PHASE 11
PHASE 2
(390)
300
30
CLKOUT
CLKOUT
4608A F02
13
4608afc
4608 F02
4608A F03