CS5165AGDWR16G ON Semiconductor, CS5165AGDWR16G Datasheet - Page 15

• Manufacturer Part Number: CS5165AGDWR16G
• Description: IC CTRLR BUCK SYNC 5BIT 16-SOIC
• Manufacturer: ON Semiconductor

Specifications of CS5165AGDWR16G

• Applications: Controller, Intel Pentium® II
• Voltage - Input: 8 ~ 14 V
• Number Of Outputs: 2
• Voltage - Output: 1.34 ~ 2.09 V, 2.14 ~ 3.54 V
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 16-SOIC (0.300", 7.5mm Width)
• Mounting Style: SMD/SMT
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Droop Resistor Tolerance
voltage drop across it at full load has to be calculated. This
voltage drop has to be such that the output voltage full load
is above the minimum DC tolerance spec.
is 2.74 < V
2.67 V < V
voltage is +2.812 V < V
exceed the DC accuracy spec, the voltage drop developed
across the resistor must be calculated as follows:
error amplifier’s reference voltage is trimmed so that the
output voltage will be 40 mV high at no load. With no load,
there is no DC drop across the resistor, producing an output
voltage tracking the error amplifier output voltage, including
the offset. When the full load current is delivered, a drop of
−56 mV is developed across the resistor. Therefore, the
regulator output is pre−positioned at 40 mV above the
nominal output voltage before a load turn−on. The total
voltage drop due to a load step is DV−40 mV and the
deviation from the nominal output voltage is 40 mV smaller
than it would be if there was no droop resistor. Similarly at full
load the regulator output is pre−positioned at 16 mV below
the nominal voltage before a load turn−off. The total voltage
increase due to a load turn−off is DV−16 mV and the
deviation from the nominal output voltage is 16 mV smaller
than it would be if there was no droop resistor. This is because
the output capacitors are pre−charged to value that is either
40 mV above the nominal output voltage before a load
turn−on or, 16 mV below the nominal output voltage before
a load turn−off (see Figure 15).
resistor ( the larger the resistance), the worse the DC and
load regulation, but the better the AC transient response.
Design Rules for Using a Droop Resistor
where:
V DROOP(TYP) +
Tolerance due to sheet resistivity variation
Tolerance due to L/W error
Tolerance due to temperature variation
Total tolerance for droop resistor
In order to determine the droop resistor value the nominal
Example: for a 300 MHz PentiumII, the DC accuracy spec
With the CS5165A DAC accuracy being 1.0%, the internal
Obviously, the larger the voltage drop across the droop
The basic equation for laying an embedded resistor is:
A = W × t = cross−sectional area
ρ = the copper resistivity (mW − mil)
L = length (mils)
W = width (mils)
t = thickness (mils)
V DROOP(TYP) +
CC(CORE)
CC(CORE)
R AR + ò
+ 2.812 V * 2.74 V
[V DAC(MIN) * V DC PENTIUMII(MIN)]
< 2.9 V, and the AC accuracy spec is
< 2.9 3V. The CS5165A DAC output
1 ) R DROOP(TOLERANCE )
1 ) R DROOP(TOLERANCE )
A
L
DAC
[V DAC(MIN) * V DC(MIN) ]
1.3
or R + ò
< +2.868 V. In order not to
+ 56 mV
(W
L
t)
http://onsemi.com
16%
1.0%
12%
29%
CS5165A
15
mils) for one ounce copper. ρ = 717.86 mW−mil
create a 56 mV drop at full load is:
temperature according to the following guidelines:
Droop Resistor Width Calculations
current and therefore requires a minimum width which is
calculated as follows (assume one ounce copper thickness):
where:
dissipation, and I
Therefore:
Output Inductor
current capability, and DC resistance. Increasing the
inductor value will decrease output voltage ripple, but
degrade transient response.
Inductor Ripple Current
Example: V
L = 1.2 mH, Freq = 200 kHz
Output Ripple Voltage
V RIPPLE + Inductor Ripple Current
Example:
Switching Frequency = 200 kHz
(from manufacturer’s specs)
Ripple Current +
For most PCBs the copper thickness, t, is 35 mm (1.37
For a Pentium II load of 14.2 A the resistance needed to
The resistivity of the copper will drift with the
The droop resistor must have the ability to handle the load
W = minimum width (in mils) required for proper power
The Pentium
Droop Resistor Length Calculation
The inductor should be selected based on its inductance,
V
Output Ripple Voltage = 5.1 A × Output Capacitor ESR
ESR of Output Capacitors to limit Output Voltage Spikes
Ripple Current +
IN
L +
Response Droop + 56 mV
= +5.0 V, V
+ 0.0039
W + 14.2 A
R DROOP
IN
DR + 34% @ T A + ) 100°C
DR + 12% @ T A + ) 50°C
= +5.0 V, V
®
II maximum load current is 14.2 A.
0.05
LOAD
OUT
717.86
ò
[200 kHz
284
(Switching Frequency
[(5.0 V * 2.8 V)
ESR +
= +2.8 V, I
W +
+ 284 mils + 0.7213 cm
Load Current Amps.
W
[(V IN * V OUT )
OUT
I OUT
1.37
I LOAD
DV OUT
t
0.05
DI OUT
= +2.8 V, I
1.2 mH
LOAD
+ 2113 mil + 5.36 cm
+ 56 mV
14.2 A
Output Capacitor ESR
= 14.2 A, L = 1.2 mH,
2.8 V]
5.0 V]
LOAD
+ 3.9 mW
V OUT ]
L
+ 5.1 A
= 14.2 A,
V IN )