CS5212GD14 ONSEMI [ON Semiconductor], CS5212GD14 Datasheet - Page 10

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CS5212GD14

Manufacturer Part Number
CS5212GD14
Description
Low Voltage Synchronous Buck Controller
Manufacturer
ONSEMI [ON Semiconductor]
Datasheets

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Part Number
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Part Number:
CS5212GD14
Manufacturer:
ON Semiconductor
Quantity:
110
where;
copper clad circuit boards will have approximate thermal
resistances (
should be performed to insure the design will dissipate the
required power under worst case operating conditions.
Variables considered during testing should include
maximum ambient temperature, minimum airflow,
maximum input voltage, maximum loading, and component
variations (i.e. worst case MOSFET R
inductors and capacitors share the MOSFET’s heatsinks and
will add heat and raise the temperature of the circuit board
and MOSFET. For any new design, its advisable to have as
much heatsink area as possible – all too often new designs
are found to be too hot and require re–design to add
heatsinking.
Compensation Capacitor Selection
30 A. This current charging the capacitor on the COMP pin
is used as soft start for the converter. The COMP pin is going
to ramp up to a voltage level that is within 70 mV of what
V
that will determine the soft start. Therefore, the COMP
capacitor can be established by the following relationship:
where:
FFB
T
T
For TO–220 and TO–263 packages, standard FR–4
As with any power design, proper laboratory testing
The nominal output current capability of the error amp is
soft start = output ramp–up time
V
30 A = COMP output current, typ.
T
JC
SA
A
J
FFB(REG)
MOSFET.
heatsink assuming direct mounting of the MOSFET (no
thermal “pad” is used).
temperature.
is the total thermal impedance (
is the worst case ambient operating temperature.
is going to be when in regulation. This is the voltage
is the junction–to–case thermal impedance of the
is the specified maximum allowed junction
is the sink–to–ambient thermal impedance of the
SA
= V
) as shown below:
(in
Pad Size
0.75/484
2.0/1290
2.5/1612
C + 30 mA
0.5/323
1.0/645
1.5/968
FFB
2
q T t (T J * T A ) P D
/mm
voltage when in regulation
2
)
V FFB(REG)
Single–Sided
1 oz. Copper
soft start
60–65 C/W
55–60 C/W
50–55 C/W
45–50 C/W
38–42 C/W
33–37 C/W
JC
DS(on)
+
SA
). Also, the
).
http://onsemi.com
CS5212
10
and will affect the ramp–up time. The value of the capacitor
on the COMP pin will have an effect on the loop response
and the transient response of the converter. Transient
response can be enhanced by the addition of a parallel
combination of a resistor and capacitor between the COMP
pin and the comp capacitor.
R
resistor connected between the R
The grounded side of this resistor should be directly
connected to the SGND pin, without any other currents
flowing between the bottom of the resistor and the pin. Also,
avoid running any noisy signals under the resistor, since
injected noise could cause frequency jitter. The graph in
Figure NO TAG shows the required resistance to program
the frequency. Below 500 kHz, the following formula is
accurate:
where f
Differential Remote Sense Operation
provided by the CS5212. The positive remote sense is
implemented by bringing the output remote sense
connection to the positive load connection. A low value
resistor is connected from Vout to the feedback point at the
regulator to provide feedback in the instance when the
remote sense point is not connected.
connecting the SGND of the CS5212 to the negative of the
load return. Again, a low value resistor should be connected
between SGND and LGND at the regulator to provide
feedback in the instance when the remote sense point is not
connected. The maximum voltage differential between the
three grounds for this part is 200 mV.
OSC
The COMP output current range is given in the data sheet
The switching frequency is programmed by selecting the
The ability to implement fully differential remote sense is
The negative remote sense connection is provided by
140
120
100
80
60
40
20
0
Selection
0
SW
is the switching frequency in kHz.
100
Figure 6. Frequency vs. R
R + 17544 f SW * 4 kW
200
300
Frequency (kHz)
400
OSC
500
pin and SGND (pin 7).
OSC
600
700
800

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