CS5165A Ver la hoja de datos (PDF) - ON Semiconductor
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CS5165A Datasheet PDF : 18 Pages
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CS5165A
This applies for current spikes that are faster than
regulator response time. Printed Circuit Board resistance
will add to the ESR of the output capacitors.
In order to limit spikes to 100 mV for a 14.2 A Load Step,
ESR = 0.1/14.2 = 0.007 W
Inductor Peak Current
ǒ Ǔ Peak Current + Maximum Load Current )
Ripple Current
2
Example: VIN = +5.0 V, VOUT = +2.8 V, ILOAD = 14.2 A,
L = 1.2 mH, Freq = 200 kHz
Peak Current + 14.2 A ) (5.1ń2) + 16.75 A
A key consideration is that the inductor must be able to
deliver the Peak Current at the switching frequency without
saturating.
Response Time to Load Increase
(limited by Inductor value unless Maximum On−Time is
exceeded)
Response
Time
+
L
(VIN
DIOUT
* VOUT)
Example: VIN = +5.0 V, VOUT = +2.8 V, L = 1.2 mH, 14.2 A
change in Load Current
Response
Time
+
1.2 mH
(5.0 V
*
14.2 A
2.8 V)
+
7.7
ms
Response Time to Load Decrease
(limited by Inductor value)
Response Time + L
Change in IOUT
VOUT
Example: VOUT = +2.8 V, 14.2 A change in Load Current,
L = 1.2 mH
Response
Time
+
1.2
mH
2.8
14.2
V
A
+
6.1
ms
Input and Output Capacitors
These components must be selected and placed carefully to
yield optimal results. Capacitors should be chosen to provide
acceptable ripple on the input supply lines and regulator
output voltage. Key specifications for input capacitors are
their ripple rating, while ESR is important for output
capacitors. For best transient response, a combination of low
value/high frequency and bulk capacitors placed close to the
load will be required.
THERMAL MANAGEMENT
Thermal Considerations for Power
MOSFETs and Diodes
In order to maintain good reliability, the junction
temperature of the semiconductor components should be
kept to a maximum of 150°C or lower. The thermal
impedance (junction to ambient) required to meet this
requirement can be calculated as follows:
Thermal
Impedance
+
TJUNCTION(MAX) *
Power
TAMBIENT
A heatsink may be added to TO−220 components to reduce
their thermal impedance. A number of PC board layout
techniques such as thermal vias and additional copper foil
area can be used to improve the power handling capability of
surface mount components.
EMI Management
As a consequence of large currents being turned on and off
at high frequency, switching regulators generate noise as a
consequence of their normal operation. When designing for
compliance with EMI/EMC regulations, additional
components may be added to reduce noise emissions. These
components are not required for regulator operation and
experimental results may allow them to be eliminated. The
input filter inductor may not be required because bulk filter and
bypass capacitors, as well as other loads located on the board
will tend to reduce regulator di/dt effects on the circuit board
and input power supply. Placement of the power component to
minimize routing distance will also help to reduce emissions.
Layout Guidelines
When laying out the CPU buck regulator on a printed
circuit board, the following checklist should be used to ensure
proper operation of the CS5165A.
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