US3012/3012A

4-1

Rev. 1.0
5/6/98

TYPICAL APPLICATION

DESCRIPTION

The US3012 family of controller ICs are specifically de-
signed to meet Intel specification for Pentium II

and

Pentium Pro

microprocessor applications as well as

the next generation P6 family processors. These prod-
ucts feature a patented topology that in combination
with a few external components as shown in the typical
application circuit below ,will provide in excess of 16A
of output current for an on- board DC/DC converter while
automatically providing the right output voltage via the 5
bit internal DAC .These devices also feature, loss less
current sensing by using the Rds-on of the high side
Power MOSFET as the sensing resistor, a Power Good
window comparator that switches its open collector out-
put low when the output is outside of a

10% window .

Other features of the device are ; Undervoltage lockout
for both 5V and 12V supplies as well as an external
programmable soft start function as well as program-
ming the oscillator frequency by using an external ca-
pacitor.

Dual Layout Compatible with RC5051
Designed to meet Intel specification of VRM8.2
& VRM8.3 for Pentium II

On board DAC programs the output voltage
from 1.3V to 3.5V (US3010) & 1.8V to 3.5V for
US3010A
Loss less Short Circuit Protection
Synchronous operation allows maximum
efficiency
Patented architecture allows fixed frequency
operation as well as 100% duty cycle during
dynamic load
Soft Start
High current totem pole driver for direct
driving of the external Power MOSFET
Power Good function

PACKAGE ORDER INFORMATION

PRELIMINARY DATASHEET

FEATURES

5 BIT PROGRAMMABLE SYNCHRONOUS BUCK

CONTROLLER IC

APPLICATIONS

Pentium II & Pentium Pro

processor DC to DC

converter application
Low cost Pentium with AGP

Notes: Pentium II and Pentium Pro are
trade marks of Intel Corp.

12V

VID0

Power Good

3012app1-1.1

OutEn

VID1

VID2

VID3

VID4

C11

R12

R13

HDrv

LDrv

NC/Vccp

SS/Vref

CS+

Gnd

Vfb/

GndD

US3012

PGd

CS-

V12

NC/

GndA

NC/

GndP

R10

R11

C10

Ta (

Device Package VID Voltage Range

0 TO 70

US3012CW 20 pin Plastic SOIC WB 1.3V to 3.5V

0 TO 70

US3012ACW 20 pin Plastic SOIC WB 1.8V to 3.5V

4-2

Rev. 1.0

5/6/98

US3012/3012A

ELECTRICAL SPECIFICATIONS

Unless otherwise specified ,these specifications apply over ,V12 = 12V, V5 = 5V and Ta=0 to 70

C. Typical values

refer to Ta =25

C. Low duty cycle pulse testing are used which keeps junction and case temperatures equal to the

ambient temperature.

ABSOLUTE MAXIMUM RATINGS

V5 supply Voltage ........................................... 7V
V12 Supply Voltage ............................................ 20V
Storage Temperature Range ................................. -65 TO 150

Operating Junction Temperature Range .......... 0 TO 125

PACKAGE INFORMATION

20 PIN WIDE BODY PLASTIC SOIC (W)

=85

C/W

PARAMETER

SYM TEST CONDITION

MIN

TYP

MAX

UNITS

VID Section
DAC output voltage

0.99Vs

1.01Vs

(note 1)
DAC Output Line Regulation

0.1

DAC Output Temp Variation

0.5

VID Input LO

0.4

VID Input HI

VID input internal pull-up

resistor to V5
Power Good Section
Under voltage lower trip point

Vout ramping down

0.89Vs

0.90Vs

0.91Vs

Under voltage upper trip point

Vout ramping up

0.92Vs

UV Hysterises

.015Vs

.02Vs

.025Vs

Over voltage upper trip point

Vout ramping up

1.09Vs

1.10Vs

1.11Vs

Over voltage lower trip point

Vout ramping down

1.08Vs

OV Hysterises

.015Vs

.02Vs

.025Vs

Power Good Output LO

RL=3mA

0.4

Power Good Output HI

RL=5K pull up to 5V

4.8

Soft Start Section
Soft Start Current

CS+ =0V , CS- =5V

TOP VIEW

Gnd

Vfb

V12

HDrv

PGd

CS+

CS-

LDrv

PGnd

US3012/3012A

4-3

Rev. 1.0
5/6/98

UVLO Section
UVLO Threshold-12V

Supply ramping up

9.2

10.8

UVLO Hysterises-12V

0.3

0.4

0.5

UVLO Threshold-5V

Supply ramping up

4.1

4.3

4.5

UVLO Hysterises-5V

0.2

0.3

0.4

Error Comparator Section
Input bias current

Input Offset Voltage

-2

Delay to Output

Vdiff=10mV

100

Current Limit Section
C.S Threshold Set Current

160

200

240

C.S Comp Offset Voltage

-5

Hiccup Duty Cycle

Css=0.1 uF

Supply Current
Operating Supply Current

CL=3000pF
V5

V12

Output Drivers Section
Rise Time

CL=3000pF

100

Fall Time

CL=3000pF

130

Dead band Time

CL=3000pF

100

200

300

Oscillator Section
Osc Frequency

Ct=150pF

190

220

250

Khz

Osc Valley

0.2

Osc Peak

Output Enable Section
Pull up Resistor to V5

HI Threshold Voltage

LO Threshold Voltage

0.8

Note 1: Vs refers to the set point voltage given in Table 1.

1.30*

1.35*

2.1

1.40*

2.2

1.45*

2.3

1.50*

2.4

1.55*

2.5

1.60*

2.6

1.65*

2.7

1.70*

2.8

1.75*

2.9

1.80

3.0

1.85

3.1

1.90

3.2

1.95

3.3

2.00

3.4

2.05

3.5

* Output voltage is disabled for US3012A.
** Output voltage is disabled for all versions.

Table 1 - Set point voltage vs. VID codes

4-4

Rev. 1.0

5/6/98

US3012/3012A

PIN DESCRIPTIONS

Pin Description
LSB input to the DAC that programs the output voltage. This pin can be pulled up exter-
nally by a 10k resistor to either 3.3V or 5V supply.
Input to the DAC that programs the output voltage.This pin can be pulled up externally by
a 10k

resistor to either 3.3V or 5V supply.

Input to the DAC that programs the output voltage.This pin can be pulled up externally by
a 10k resistor to either 3.3V or 5V supply.
MSB input to the DAC that programs the output voltage.This pin can be pulled up exter-
nally by a 10k resistor to either 3.3V or 5V supply.
This pin selects a range of output voltages for the DAC. The voltage range for both the "A"
and the none "A" versions of the device is given in table 1.
This pin is an open collector output that switches LO when the output of the converter is
not within

10% (typ) of the nominal output voltage.When PWRGD pin switches LO the

sat voltage is less than 0.4V at 3mA.
This pin is connected directly to the output of the Core supply to provide feedback to the
Error comparator.
This pin is connected to the Drain of the power MOSFET of the Core supply and it
provides the positive sensing for the internal current sensing circuitry. An external resis-
tor programs the C.S threshold depending on the Rds of the power MOSFET. An external
capacitor is placed in parallel with the programming resistor to provide high frequency
noise filtering.
This pin is connected to the Source of the power MOSFET for the Core supply and it
provides the negative sensing for the internal current sensing circuitry.
This pin provides the soft start for the switching regulator. An internal current source
charges an external capacitor that is conected from this pin to the GND which ramps up
the outputs of the switching regulator, preventing the outputs from overshooting as wellas
limiting the input current. The second function of the Soft Start cap is to provide long off
time for the synchronous MOSFET or the Catch diode (HICCUP) during current limiting.
This pin programs the oscillator frequency in the range of 50 kHZ to 500kHZ with an
external capacitor connected from this pin to the GND.
This pin serves as the ground pin and must be conected directly to the ground plane. A
high frequency capacitor (0.1 to 1 uF) must be connected from V5 and V12 pins to this
pin for noise free operation.
Output driver for the synchronous power MOSFET.
Output driver for the high side power MOSFET.
This pin is connected to the 12 V supply and serves as the power Vcc pin for the output
drivers.A high frequency capacitor (0.1 to 1 uF) must be connected directly from this pin
to GND pin in order to supply the peak current to the power MOSFET during the transi-
tions.
5V supply voltage.
This is the output enable pin.This pin is internally pulled high through a resistor to 5V
supply. A low signal on this pin disables the output.
No connect.

PIN# PIN SYMBOL
20

PGd

Vfb

CS+

CS-

Gnd

LDrv

HDrv

V12

OUTEN

7,11

N.C

4-6

Rev. 1.0

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US3012/3012A

TYPICAL APPLICATION

SYNCHRONOUS OPERATION
(Dual Layout with RC5051)

Typical application of US3012/3012A in an on board DC-DC converter providing the Core supply for the Pentium II

microprocessor.

Table of components that need to be modified to make the dual layout work for US3012A* and RC5051.

Part #

R10

R11

RC5051

US3012A* S

S - Short

O - Open

V - See Unisem or Raytheon parts list for the value.

* Table also applies to the none "A" version of the part.
Note 1 : R8 can be replaced with shorting wire of #20 AWG or lower. This elliminates the expensive current
sense resistor that otherwise is needed with RC5051.

12V

VID0

Power Good

3012app1-1.1

OutEn

VID1

VID2

VID3

VID4

C11

R12

R13

HDrv

LDrv

NC/Vccp

SS/Vref

CS+

Gnd

Vfb/

GndD

US3012

PGd

CS-

V12

NC/

GndA

NC/

GndP

R10

R11

C10

US3012/3012A

4-7

Rev. 1.0
5/6/98

US3012/3012A and RC5051 Dual Layout Parts List

Ref Desig

Description

Qty

Part #

Manuf

MOSFET

IRL3103
IRL3103S (Note 1)

MOSFET

IRL3103
IRL3103S (Note 1)

Inductor

L=1 uH

Inductor

Core:T50-18
Turns:14 AWG
L=2.5 uH R=2 mohm

Micro Metal

Diode

open

C11

Capacitor ,Electrolytic

6MV1500GX ,1500uF,6.3V,

Sanyo

Capacitor ,Electrolytic

6MV1500GX ,1500uF,6.3V,

Sanyo

Capacitor ,Electrolytic

680uF,10V, EEUFA1A681L

Panasonic

Capacitor , Ceramic

1 uF , SMT

Capacitor , Ceramic

1 uF , SMT

Capacitor , Ceramic

220 pF , SMT

Capacitor , Ceramic

1 uF , SMT

Capacitor , Ceramic

470 pF , SMT

Capacitor , Ceramic

150pF , X7R , SMT

Capacitor , Ceramic

0.01 uF , SMT

C10

Capacitor , Ceramic

0.01 uF , SMT

Resistor

Short, SMT

Resistor

2.21 k

, 1% ,SMT

Resistor

, 5%, SMT , 1206 size

Resistor

Short, SMT

Resistor

, 5%, SMT , 1206 size

Resistor

, 5%, SMT , 1206 size

Resistor

open , SMT

Resistor

short , #20 AWG wire

Resistor

open , SMT

R10

Resistor

100

, 1%, SMT

R11

Resistor

10 k

, 1% ,SMT

R12

Resistor

100 k

, 5%, SMT

R13

Resistor

See Raytheon Parts List , SMT

HS1

Q1 Heatsink

6270

Thermalloy

HS2

Q2 Heatsink

6270

Thermalloy

Note 1 : For the applications where it is desirable not to use the Heatsink, the IRL3103S MOSFET in the TO263
SMT package with 1

square of pad area using top and bottom layers of the board as a minimum is required.

4-8

Rev. 1.0

5/6/98

US3012/3012A

Application Information

An example of how to calculate the components for the
application circuit is given below.
Assuming, two sets of output conditions that this regu-
lator must meet,
a) Vo=2.8V , Io=14.2A,

Vo=185mV,

Io=14.2A

b) Vo=2V , Io=14.2A,

Vo=140mV,

Io=14.2A

The regulator design will be done such that it meets the
worst case requirement of each condition.

Output Capacitor Selection

The first step is to select the output capacitor. This is
done primarily by selecting the maximum ESR value
that meets the transient voltage budget of the total

specification. Assuming that the regulators DC initial
accuracy plus the output ripple is 2% of the output volt-
age, then the maximum ESR of the output capacitor is
calculated as :

ESR

100

14 2

The Sanyo M V G X series is a good choice to achieve

both the price and perform ance goals. The 6M V 1500G X

, 1500uF, 6.3V has an E S R of less than 36 m

typ .

Selecting 6 of these capacitors in parallel has an ESR
of

6 m

which achieves our low ESR goal.

Other type of Electrolytic capacitors from other manu-
facturers to consider are the Panasonic "FA" series or
the Nichicon "PL" series.

Reducing the Output Capacitors Using Voltage Level
Shifting Technique

The trace resistance or an external resistor from the output
of the switching regulator to the Slot 1 can be used to
the circuit advantage and possibly reduce the number
of output capacitors, by level shifting the DC regu-
lation point when transitioninig from light load to
full load and vice versa. To accomplish this, the out-
put of the regulator is typically set about half the DC
drop that results from light load to full load. For example,
if the total resistance from the output capacitors to the
Slot 1 and back to the GND pin of the device is 5m

and

if the total

I, the change from light load to full load is

This intentional voltage level shifting during the load tran-
sient eases the requirement for the output capacitor ESR
at the cost of load regulation. One can show that the
new ESR requirement eases up by half the total trace
resistance. For example, if the ESR requirement of the
output capacitors without voltage level shifting must be
7m

then after level shifting the new ESR will only need

to be 8.5m

if the trace resistance is 5m

(7+5/2=9.5).

However, one must be careful that the combined "volt-
age level shifting" and the transient response is still within
the maximum tolerance of the Intel specification. To in-
sure this, the maximum trace resistance must be less
than:
Rs

2(Vspec - 0.02*Vo -

Vo)/

Where :
Rs=Total maximum trace resistance allowed
Vspec=Intel total voltage spec
Vo=Output voltage

Vo=Output ripple voltage

I=load current step

For example, assuming:
Vspec=

140 mV=

0.1V for 2V output

Vo=2V

Vo=assume 10mV=0.01V

I=14.2A

Then the Rs is calculated to be:
Rs

2(0.140 - 0.02*2 - 0.01)/14.2=12.6m

However, if a resistor of this value is used, the maximum
power dissipated in the trace (or if an external resistor is
being used) must also be considered. For example if
Rs=12.6 m

, the power dissipated is

(Io^2)*Rs=(14.2^2)*12.6=2.54W. This is a lot of power to
be dissipated in a system. So, if the Rs=5m

, then the

power dissipated is about 1W which is much more ac-
ceptable. If level shifting is not implemented, then the
maximum output capacitor ESR was shown previously
to be 7m

which translated to

6 of the 1500uF,

6MV1500GX type Sanyo capacitors. With Rs=5m

, the

maximum ESR becomes 9.5m

which is equivalent to

4 caps. Another important consideration is that if a

trace is being used to implement the resistor, the
power dissipated by the trace increases the case
temperature of the output capacitors which could
seriously effect the life time of the output capaci-
tors.

Output Inductor Selection

The output inductance must be selected such that un-
der low line and the maximum output voltage condition,
the inductor current slope times the output capacitor
ESR is ramping up faster than the capacitor voltage is

US3012/3012A

4-9

Rev. 1.0
5/6/98

drooping during a load current step. However if the in-
ductor is too small , the output ripple current and ripple
voltage become too large. One solution to bring the ripple
current down is to increase the switching frequency ,
however that will be at the cost of reduced efficiency and
higher system cost. The following set of formulas are
derived to achieve the optimum performance without
many design iterations.
The maximum output inductance is calculated using the
following equation :

L = E S R * C * ( V inm in - Vom ax ) / ( 2*

I )

Where :
Vinmin = Minimum input voltage
For Vo = 2.8 V ,

I = 14.2 A

L =0.006 * 9000 * ( 4.75 - 2.8) / (2 * 14.2) = 3.7 uH
Assuming that the programmed switching frequency is
set at 200 KHZ , an inductor is designed using the
Micrometals' powder iron core material. The summary
of the design is outlined below :
The selected core material is Powder Iron , the
selected core is T50-52D from Micro Metal wounded
with 8 Turns of # 16 AWG wire, resulting in 3 uH
inductance with

3 m

of DC resistance.

Assuming L = 3 uH and the switching frequency ; Fsw =
200 KHZ , the inductor ripple current and the output
ripple voltage is calculated using the following set of
equations :
T = 1/Fsw
T

Switching Period

( Vo + Vsync ) / ( Vin - Vsw + Vsync )

Duty Cycle

Ton = D * T
Vsw

High side Mosfet ON Voltage = Io * Rds

Rds

Mosfet On Resistance

Toff = T - Ton
Vsync

Synchronous MOSFET ON Voltage=Io * Rds

Ir = ( Vo + Vsync ) * Toff /L

Inductor Ripple Current

Vo =

Ir * ESR

Output Ripple Voltage

In our example for Vo = 2.8V and 14.2 A load , Assum-
ing IRL3103 MOSFET for both switches with maximum
on resistance of 19 m

, we have :

T = 1 / 200000 = 5 uSec
Vsw =Vsync= 14.2*0.019=0.27 V
D

( 2.8 + 0.27 ) / ( 5 - 0.27 + 0.27 ) = 0.61

Ton = 0.61 * 5 = 3.1 uSec
Toff = 5 - 3.1 = 1.9 uSec

Ir = ( 2.8 + 0.27 ) * 1.9 / 3 = 1.94 A

Vo = 1.94 * .006 = .011 V = 11 mV

Power Component Selection

Assuming IRL3103 MOSFETs as power components,
we will calculate the maximum power dissipation as fol-
lows:
For high side switch the maximum power dissipation
happens at maximum Vo and maximum duty cycle.
Dmax

( 2.8 + 0.27 ) / ( 4.75 - 0.27 + 0.27 ) = 0.65

Pdh = Dmax * Io^2*Rds(max)
Pdh= 0.65*14.2^2*0.029=3.8 W
Rds(max)=Maximum Rds-on of the MOSFET at 125

For synch MOSFET, maximum power dissipation hap-
pens at minimum Vo and minimum duty cycle.
Dmin

( 2 + 0.27 ) / ( 5.25 - 0.27 + 0.27 ) = 0.43

Pds = (1-Dmin)*Io^2*Rds(max)
Pds=(1 - 0.43) * 14.2^2 * 0.029 = 3.33 W

Heatsink Selection

Selection of the heat sink is based on the maximum
allowable junction temperature of the MOSFETS. Since
we previously selected the maximum Rds-on at 125

then we must keep the junction below this temperature.
Selecting TO220 package gives

jc=1.8

C/W ( From the

venders' datasheet ) and assuming that the selected
heatsink is Black Anodized , the Heat sink to Case ther-
mal resistance is ;

cs=0.05

C/W , the maximum heat

sink temperature is then calculated as :
Ts = Tj - Pd * (

jc +

cs)

Ts = 125 - 3.82 * (1.8 + 0.05) = 118

With the maximum heat sink temperature calculated in
the previous step, the Heat Sink to Air thermal resis-
tance (

sa) is calculated as follows :

Assuming Ta=35

T = Ts - Ta = 118 - 35 = 83

C Temperature Rise

Above Ambient

sa =

T/Pd

sa = 83 / 3.82 = 22

C/W

Next , a heat sink with lower

sa than the one calcu-

lated in the previous step must be selected. One way to
do this is to simply look at the graphs of the "Heat Sink
Temp Rise Above the Ambient" vs. the "Power Dissipa-
tion" given in the heatsink manufacturers' catalog and
select a heat sink that results in lower temperature rise
than the one calculated in previous step. The following
heat sinks from AAVID and Thermaloy meet this crite-
ria.
Co.

Part #

Thermalloy

6078B

AAVID

577002

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5/6/98

US3012/3012A

Following the same procedure for the Schottcky diode
results in a heatsink with

sa = 25

C/W. Although it is

possible to select a slightly smaller heatsink, for sim-
plicity the same heatsink as the one for the high side
MOSFET is also selected for the synchronous MOSFET.

Switcher Current Limit Protection

The PWM controller uses the MOSFET Rds-on as the
sensing resistor to sense the MOSFET current and com-
pares to a programmed voltage which is set externally
via a resistor (Rcs) placed between the drain of the
MOSFET and the "CS+" terminal of the IC as shown in
the application circuit. For example, if the desired cur-
rent limit point is set to be 22A and from our previous

selection, the m axim um M O S F E T R ds-on=19m

, then

the current sense resistor, Rcs is calculated as :
Vcs=IcL*Rds=22*0.019=0.418V
Rcs=Vcs/Ib=(0.418V)/(200uA)=2.1k

Where: Ib=200uA is the internal current setting of the
device

Switcher Timing Capacitor Selection

The switching frequency can be programmed using an
external timing capacitor. The Ct value can be approxi-
mated using the equation below:

Switcher Output Voltage Adjust

As it was discussed earlier,the trace resistance from
the output of the switching regulator to the Slot 1 can be
used to the circuit advantage and possibly reduce the
number of output capacitors, by level shifting the DC
regulation point when transitioninig from light load to full
load and vice versa. To account for the DC drop, the
output of the regulator is typically set about half the DC
drop that results from light load to full load. For example,
if the total resistance from the output capacitors to the

Where

C =Ti

g Capacitor

Switching Frequency

3 5 10

min

If, F =

kHz :

200

3 5 10

200 10

175

Slot 1 and back to the GND pin of the device is 5m

and

if the total

I, the change from light load to full load is

14A, then the output voltage measured at the top of the
resistor divider which is also connected to the output
capacitors in this case, must be set at half of the 70 mV
or 35mV higher than the DAC voltage setting. To do this,
the top resistor of the resistor divider(R10 in the applica-
tion circuit) is set at 100

, and the R11 is calculated.

For example, if DAC voltage setting is for 2.8V and the
desired output under light load is 2.835V, then R11 is
calculated using the following formula :
R11= 100*

{

Vdac /(Vo - 1.004*Vdac)

}

[]

R11= 100*

{

2.8 /(2.835 - 1.004*2.800)

}

= 11.76 k

Select 11.8 k

, 1%

Note: The value of the top resistor must not exceed
100

. The bottom resistor can then be adjusted to raise

the output voltage.

Soft Start Capacitor Selection

The soft start capacitor must be selected such that dur-
ing the start up when the output capacitors are charging
up, the peak inductor current does not reach the current
limit treshold. A minimum of 1uF capacitor insures this
for most applications. An internal 10uA current source
charges the soft start capacitor which slowly ramps up
the inverting input of the PWM comparator Vfb3. This
insures the output voltage to ramp at the same rate as
the soft start cap thereby limiting the input current. For
example, with 1uF and the 10uA internal current source
the ramp up rate is (

t)=I/C = 1V/100mS. Assum-

ing that the output capacitance is 9000uF, the maxi-
mum start up current will be:
I=9000uF*(1V/100mS)=0.09A

Input Filter

It is highly recommended to place an inductor between
the system 5V supply and the input capacitors of the
switching regulator to isolate the 5V supply from the
switching noise that occurs during the turn on and off of
the switching components. Typically an inductor in the
range of 1 to 3 uH will be sufficient in this type of appli-
cation.

Switcher External Shutdown

The best way to shutdown the part is to pull down on the
soft start pin using an external small signal transistor
such as 2N3904 or 2N7002 small signal MOSFET. This
allows slow ramp up of the output, the same as the power
up.

US3012/3012A

4-11

Rev. 1.0
5/6/98

Layout Considerations

Switching regulators require careful attention to the lay-
out of the components, specifically power components
since they switch large currents. These switching com-
ponents can create large amount of voltage spikes and
high frequency harmonics if some of the critical compo-
nents are far away from each other and are connected
with inductive traces. The following is a guideline of how
to place the critical components and the connections
between them in order to minimize the above issues.
Start the layout by first placing the power components:

1) Place the input capacitors C3 and the high side
mosfet ,Q1 as close to each other as possible
2) Place the synchronous mosfet,Q2 and the Q1 as
close to each other as possible with the intention that
the source of Q1 and drain of the Q2 has the shortest
length.
3) Place the snubber R4 & C7 between Q1 & Q2.
4) Place the output inductor ,L2 and the output capaci-
tors ,C10 between the mosfet and the load with output
capacitors distributed along the slot 1 and close to it.
5) Place the bypass capacitors, C4 and C6 right next to
12V and 5V pins. C4 next to the 12V, pin 13 and C6
next to the 5V, pin 6.
6) Place the IC such that the pwm output drives, pins
12 and 9 are relatively short distance from gates of Q1
and Q2.
7) If the ouput voltage is to be adjusted, place resistor
dividers, R10 & R11 close to the feedback pin.
Note 1: Although, the device does not require resistor
dividers and the feedback pin can be directly connected
to the output, they can be used to set the outputs slightly
higher to account for any output drop at the load due to
the trace resistance. See the application note.
8) Place timing capacitor C8 close to pin1 and soft start
capacitor C2 close to pin 16.
Component connections:
Note : It is extremely important that no data bus
should be passing through the switching regulator
section specifically close to the fast transition nodes
such as PWM drives or the inductor voltage.
Using 4 layer board, dedicate on layer to GND, another
layer as the power layer for the 5V, 3.3V and Vcore.
Connect all grounds to the ground plane using di-
rect vias to the ground plane.
Use large low inductance/low impedance plane to con-
nect the following connections either using component
side or the solder side.
a) C3 to Q1 Drain
b) Q1 Source to Q2 Drain

c) Q2 drain to L2
d) L2 to the output capacitors, C10
e) C10 to the slot 1
f) Input filter L1 to the C3
Connect the rest of the components using the shortest
connection possible

Ð­Ð»ÐµÐºÑ‚Ñ€Ð¾Ð½Ð½Ñ‹Ð¹ ÐºÐ¾Ð¼Ð¿Ð¾Ð½ÐµÐ½Ñ‚: US3012ACW

ÐÐ»ÐµÐºÑ‚Ñ€Ð¾Ð½Ð½Ñ‹Ð¹ ÐºÐ¾Ð¼Ð¿Ð¾Ð½ÐµÐ½Ñ‚: US3012ACW