LTM4616
APPLICATIONS INFORMATION
0.60
1-PHASE
2-PHASE
3-PHASE
4-PHASE
6-PHASE
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
DUTY FACTOR (V /V
)
O
IN
4616 F04
Figure 4. Normalized Input RMS Ripple Current vs Duty Factor for One to Six Channels (Phases)
Spread Spectrum Operation
tied to ground or if it’s driven by an external frequency
synchronization signal. A capacitor value of 0.01µF to
0.1µFbeplacedfromthePLLLPFpintogroundtocontrol
the slew rate of the spread spectrum frequency change.
To ensure proper start-up, add a control ramp on the
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
ofoperationisfixedbasedontheoutputload.Thismethod
of conversion creates large components of noise at the
frequency of operation (fundamental) and multiples of the
operating frequency (harmonics).
TRACK pin with a resistor, R , from TRACK to SV and
SR
IN
a capacitor, C , from TRACK to ground:
SR
1
RSR
≥
0.592
– In 1–
•500 •C
SR
V
IN
To reduce this noise, the LTM4616 can run in spread
spectrum operation by tying the CLKIN pin to SV .
IN
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
has the benefit of spreading the switching noise over a
rangeoffrequencies,thussignificantlyreducingthepeak
noise. Spread spectrum operation is disabled if CLKIN is
Output Voltage Tracking
Output voltage tracking can be programmed externally
using the TRACK pin. The output can be tracked up and
downwithanotherregulator.Themasterregulator’soutput
is divided down with an external resistor divider that is the
sameastheslaveregulator’sfeedbackdividertoimplement
4616fe
15
For more information www.linear.com/LTM4616
LINEAR_DIMENSIONS [ Linear Dimensions ]
