cs5165 ON Semiconductor, cs5165 Datasheet - Page 13

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

current suddenly increases from its minimum level, the
output capacitor is pre−positioned +40 mV. Conversely,
when load current suddenly decreases from its maximum
level, the output capacitor is pre−positioned −40 mV (see
Figures 15, 16, and 17). For best Transient Response, a
combination of a number of high frequency and bulk output
capacitors are usually used.
to a sudden increase in Load current, a normal off−time
occurs to prevent saturation of the output inductor.
If the Maximum On−Time is exceeded while responding
Trace 3− Load Current (5.0 A/10 mV/div.)
Trace 4− V
Figure 15. Output Voltage Transient Response to
a 14 A Load Pulse, V
Figure 16. Output Voltage Transient Response to a
Trace 1− GATE(H) (10 V/div.)
Trace 2− Inductor Switching Node (5.0 V/div.)
Trace 3− Load Current (5.0 A/div)
Trace 4− V
14 A Load Step, V
OUT
OUT
(100 mV/div.)
(100 mV/div.)
OUT
OUT
= +2.84 V (DAC = 10111)
= +2.84 V (DAC = 10111)
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13
Short Circuit Protection
provided, requiring only the Soft Start capacitor to
implement. If a short circuit condition occurs the V
comparator sets the FAULT latch. This causes the top FET
to shut off, disconnecting the regulator from it’s input
voltage. The Soft Start capacitor is then slowly discharged
by a 2.0 μA current source until it reaches it’s lower 0.7 V
threshold. The regulator will then attempt to restart
normally, operating in it’s extended off time mode with a
50% duty cycle, while the Soft Start capacitor is charged
with a 60 μA charge current.
will not achieve the 1.0 V low V
before the Soft Start capacitor is charged to it’s upper 2.5 V
threshold. If this happens the cycle will repeat itself until the
short is removed. The Soft Start charge/discharge current
ratio sets the duty cycle for the pulses (2.0 μA/60 μA =
3.3%), while actual duty cycle is half that due to the
extended off time mode (1.65%).
regulator components, input power supply, and PC board
traces than occurs with constant current limit protection (see
Figures 18 and 19).
will rise above the 1.0 V level, preventing the FAULT latch
from being set, allowing normal operation to resume.
Figure 17. Output Voltage Transient Response to a 14
A lossless hiccup mode short circuit protection feature is
If the short circuit condition persists, the regulator output
This protection feature results in less stress to the
If the short circuit condition is removed, output voltage
PROTECTION AND MONITORING FEATURES
A Load Turn−Off, V
Trace 1− GATE(H) (10 V/div.)
Trace 2− Inductor Switching Node (5.0 V/div.)
Trace 3− Load Current (5.0 A/div)
Trace 4− V
OUT
(100 mV/div.)
OUT
= +2.84 V (DAC = 10111)
FB
comparator threshold
FB
low