DC1245A Linear Technology, DC1245A Datasheet - Page 14

• Manufacturer Part Number: DC1245A
• Description: BOARD DEMO LTM4616
• Manufacturer: Linear Technology
• Series: µModuler

Specifications of DC1245A

• Design Resources: LTM4616 Spice Model LTM4616 Gerber Files DC1245 Design Files
• Main Purpose: DC/DC, Step Down
• Outputs And Type: 2, Non-Isolated
• Power - Output: -
• Voltage - Output: 1.2V, 1.8V
• Current - Output: 8A, 8A
• Voltage - Input: 2.7 ~ 5.5 V
• Regulator Topology: Buck
• Frequency - Switching: 1.5MHz
• Board Type: Fully Populated
• Utilized Ic / Part: LTM4616
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

LTM4616
Spread Spectrum Operation
Switching regulators can be particularly troublesome where
electromagnetic interference (EMI) is concerned.
Switching regulators operate on a cycle-by-cycle basis to
transfer power to an output. In most cases, the frequency
of operation is fixed based on the output load. This method
of conversion creates large components of noise at the
frequency of operation (fundamental) and multiples of the
operating frequency (harmonics).
To reduce this noise, the LTM4616 can run in spread
spectrum operation by tying the CLKIN pin to SV
In spread spectrum operation, the LTM4616’s internal
oscillator is designed to produce a clock pulse whose
period is random on a cycle-by-cycle basis but fixed
between 70% and 130% of the nominal frequency. This
14
applications inForMation
Figure 4. Normalized Input RMS Ripple Current vs Duty Factor for One to Six Channels (Phases)
0.60
0.55
0.50
0.45
0.40
0.35
0.30
0.25
0.20
0.15
0.10
0.05
0
0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.65 0.7 0.75 0.8 0.85 0.9
1-PHASE
2-PHASE
3-PHASE
4-PHASE
6-PHASE
DUTY FACTOR (V
IN
.
has the benefit of spreading the switching noise over a
range of frequencies, thus significantly reducing the peak
noise. Spread spectrum operation is disabled if CLKIN is
tied to ground or if it’s driven by an external frequency
synchronization signal. A capacitor value of 0.01µF to
0.1µF be placed from the PLLLPF pin to ground to control
the slew rate of the spread spectrum frequency change.
To ensure proper start-up, add a control ramp on the
TRACK pin with a resistor, R
a capacitor, C
O
/V
R
IN
SR
)
≥
– In 1–




SR

 
, from TRACK to ground:
0.592
V
IN
1
4616 F04

 
• 500 • C
SR
, from TRACK to SV
SR




IN
4616fc
and