cs5165 ON Semiconductor, cs5165 Datasheet - Page 12

• Manufacturer Part Number: cs5165
• Description: 5?bit Synchronous Cpu Buck Controller
• Manufacturer: ON Semiconductor

Normal Operation
set by the C
V
changes in regulator switching frequency, duty cycle, and
output ripple in response to changes in load and line. Output
voltage ripple will be determined by inductor ripple current
working and the ESR of the output capacitors (see Figures
13 and 14).
2
During normal operation, switch off time is constant and
Trace 1− Regulator Output Voltage (1.0 V/div.)
Trace 2− Inductor Switching Node (5.0 V/div.)
Trace 1− GATE(H) (10 V/div.)
Trace 2− Inductor Switching Node (5.0 V/div.)
Trace 3− Output Inductor Ripple Current (2.0 A/div.)
Trace 4− V
control loop to maintain regulation. This results in
Ripple, 0.5 A Load, V
Figure 12. Demonstration Board Enable Startup
Figure 13. Normal Operation Showing Output
Inductor Ripple Current and Output Voltage
OUT
OFF
ripple (20 mV/div.)
capacitor. Switch on time is adjusted by the
M 10.0 μs
Waveforms
OUT
= +2.84 V (DAC = 10111)
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12
Transient Response
provides unprecedented transient response to changes in
input voltage or output current. Pulse by pulse adjustment of
duty cycle is provided to quickly ramp the inductor current
to the required level. Since the inductor current cannot be
changed instantaneously, regulation is maintained by the
output capacitor(s) during the time required to slew the
inductor current.
through a feature called “Adaptive Voltage Positioning”.
This technique pre−positions the output capacitors voltage
to reduce total output voltage excursions during changes in
load.
reference voltage to be targeted +40 mV high without
compromising DC accuracy. A “Droop Resistor”,
implemented through a PC board trace, connects the Error
Amps feedback pin (V
and carries the output current. With no load, there is no DC
drop across this resistor, producing an output voltage
tracking the Error amps, including the +40 mV offset. When
the full load current is delivered, an 80 mV drop is developed
across this resistor. This results in output voltage being
offset −40 mV low.
additional margin is provided for a load transient before
reaching the output voltage specification limits. When load
The CS5165 V
Overall load transient response is further improved
Holding tolerance to 1.0% allows the error amplifiers
The result of Adaptive Voltage Positioning is that
Ripple, I
Trace 1− GATE(H) (10 V/div.)
Trace 2− Inductor Switching Node (5.0 V/div.)
Trace 3− Output Inductor Ripple Current (2.0 A/div.)
Trace 4− V
Figure 14. Normal Operation Showing Output
Inductor Ripple Current and Output Voltage
LOAD
OUT
ripple (20 mV/div.)
= 14 A, V
2
control loop’s 100 ns reaction time
FB
) to the output capacitors and load
OUT
= +2.84 V (DAC = 10111)