Datasheet

SC4518
600kHz, 2A Step-Down
Switching Regulator
POWER MANAGEMENT
Description
Features
The SC4518 is a current mode switching regulator with
an integrated switch, operating at 600kHz with separate
sync and enable functions. The integrated switch allows
for cost effective low power solutions (peak switch current
2 amps). The sync function allows customers to
synchronize to a faster clock in order to avoid frequency
beating in noise sensitive applications. High frequency
of operation allows for very small passive components.
Current mode operation allows for fast dynamic response
and instantaneous duty cycle adjustment as the input
varies (ideal for CPE applications where the input is a
wall plug power).
‹
‹
‹
‹
‹
‹
‹
Wide operating voltage range: 3V to 16V
Integrated 2 Amp switch
600kHz frequency of operation
Current mode controller
Synchronizable to higher frequency up to 1.2MHz
6µA low shutdown current
SOIC-8L-EDP Lead free package. This product is
fully WEEE and RoHS compliant
Applications
‹
‹
The low shutdown current makes it ideal for portable ‹
applications where battery life is important.
‹
XDSL modems
CPE equipment
DC-DC point of load applications
Portable equipment
The SC4518 is a 600kHz switching regulator
synchronizable to a faster frequency from 750kHz to
1.2MHz.
Typical Application Circuit
D1
C1
1
2
VIN
5
Enable
C3
8
BST
IN
SW
SC4518
EN
SYNC
FB
GND
4
COMP
L1
3
VOUT
R1
6
7
C4
C2
D2
R2
R3
Revision: April 18, 2007
1
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SC4518
POWER MANAGEMENT
Absolute Maximum Ratings
Exceeding the specifications below may result in permanent damage to the device, or device malfunction. Operation outside of the parameters
specified in the Electrical Characteristics section is not implied. Exposure to Absolute Maximum rated conditions for extended periods of time may
affect device reliability.
Parameter
Symbol
Limits
Units
VIN
-0.3 to +24
V
(VBST - VSW)
16
V
Boost Pin Voltage
V BST
-0.3 to +32
V
EN Pin Voltage
V EN
-0.3 to +16
V
FB Pin Voltage
V FB
-0.3 to +6
V
FB Pin Current
IFB
1
mA
SYNC Pin Current
ISYNC
1
mA
Thermal Impedance Junction to Ambient (2)
θJA
36.5
°C/W
Operating Ambient Temperature Range
TA
-40 to +85
°C
Operating Junction Temperature Range
TJ
-40 to +150
°C
Storage Temperature Range
TSTG
-65 to +150
°C
Lead Temperature (Soldering) 10 sec
TLEAD
300
°C
ESD Rating (Human Body Model)
ESD
2
kV
Input Supply Voltage
(1)
Boost Pin Above VSW
Notes:
(1) For proper operation of device, VIN should be within maximum Operating Input Voltage as defined in Electrical
Characteristics.
(2) Minimum pad size.
Electrical Characteristics
Unless specified: VIN = 12V, VCOMP = 0.8V, VBST = VIN + 5V, EN = tied to VIN, SYNC = 0, SW = open.
TA = TJ = -40°C to 125°C.
Parameter
Operati ng Input Voltage
Symbol
(1)
ISW
Osci llator Frequency
fOSC
Swi tch On Voltage D rop
VD(SW)
VIN Undervoltage Lockout
VUVLO
Standby C urrent
 2007 Semtech Corp.
Min
Typ
VIN
Maxi mum Swi tch C urrent Li mi t
VIN Supply C urrent
C onditions
Max
U nits
16
V
2.0
550
ISW = 1.5A
625
A
750
330
kHz
mV
2.60
2.9
V
IQ
VFB = VOUT(NOM) + 17%
1.0
5
mA
IQ(OFF)
VEN = 0V, VIN = 16V, VSW = 0V
5
45
µA
2
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SC4518
POWER MANAGEMENT
Electrical Characteristics (Cont.)
Unless specified: VIN = 12V, VCOMP = 0.8V, VBST = VIN + 5V, EN = tied to VIN, SYNC = 0, SW = open.
TA = TJ = -40°C to 125°C.
PARAMETER
FB Input Current
Feedback Voltage
SYMBOL
CONDITIONS
MIN
IFB
2.9V < VIN < 16V(1)
1.176
Feedback Voltage Line
Regulation
FB to VCOMP Voltage Gain(2)
FB to VCOMP
Transconductance(2)
TYP
MAX
UNITS
-0.25
-0.50
µA
1.2
1.224
V
+3
mV/V
0.4V ≤ VCOMP ≤ 0.9V
150
350
∆ ICOMP = ± 10µA
500
850
1300
µMho
VCOMP Pin Source Current
VFB = VOUT(NOM) - 17%
70
100
µA
VCOMP Pin Sink Current
VFB = VOUT(NOM) + 17%
70
100
µA
VCOMP Pin to Switch Current
Transconductance
2.5
A/V
VCOMP Pin Maximum
Switching Threshold
Duty cycle = 0%
0.35
V
VCOMP Pin Threshold
ISW = 1.5A
0.9
V
Maximum Switch Duty Cycle
Minimum Boost Voltage
Above Switch
Boost Current
 2007 Semtech Corp.
VCOMP = 1.2V, ISW = 400mA
85
%
ISW = 1.5A, 0°C ≤ TA ≤ 125°C and
ISW = 1.3A, TA < 0°C
1.8
2.7
V
ISW = 0.5A
10
15
mA
ISW = 1.5A, 0°C ≤ TA ≤ 125°C and
ISW = 1.3A, TA < 0°C
30
45
3
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SC4518
POWER MANAGEMENT
Electrical Characteristics (Cont.)
Unless specified: VIN = 12V, VCOMP = 0.8V, VBST = VIN + 5V, EN = tied to VIN, SYNC = 0, SW = open.
TA = TJ = -40°C to 125°C.
PARAMETER
Enable Input Threshold Voltage
SYMBOL
CONDITIONS
VIH
MIN
TYP
UNITS
2
V
VIL
Enable Input Bias Current
MAX
0.4
IIL
EN = 60mV above threshold
2.5
IIH
EN = 100mV below threshold
5
SYNC Threshold Voltage
V
µA
15
µA
1.5
SYNC Input Frequency (3)
700
SYNC Pin Resistance
VSYNC = 0.5V
V
1200
kHz
20
kΩ
Notes:
(1) The device is not guaranteed to function outside of its operating condition.The required minimum input voltage for a
regulated output depends on the output voltage and load condition.
(2) Guaranteed by design.
(3) For SYNC applications, please contact factory.
 2007 Semtech Corp.
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SC4518
POWER MANAGEMENT
Pin Configurations
Ordering Information
TOP VIEW
BST
1
8
SYNC
IN
2
7
COMP
SW
3
6
FB
GND
4
5
EN
Part Number (2)
Package (1)
SC4518ISTRT
SOIC-8L-EDP
S C 4518E V B
EVALUATION BOARD
Notes:
(1) Only available in tape and reel packaging. A reel
contains 2500 devices.
(2) Lead free product. This product is fully WEEE and
RoHS compliant.
(SOIC-8L-EDP)
Pin Descriptions
Pin #
Pin Name Pin Function
1
BST
This pin provides power to the internal NPN switch. The minimum turn on voltage for this switch
is 2.7V.
2
IN
Pin IN delivers all power required by control and power circuitry. This pin sees high di/dt during
switching actions of the switch. A decoupling capacitor should be attached to this pin as close as
possible.
3
SW
Pin SW is the emitter of the internal switch. The external freewheeling diode should be connected
as close as possible to this pin.
4
GND
All voltages are measured with respect to this pin. The decoupling capacitor and the freewheeling
diode should be connected to GND as short as possible.
5
EN
This is the chip enable input. The regulator is switched on if EN is high, and it is off if EN is low.
The regulator is in standby mode when EN is low, and the input supply current is reduced to a few
microamperes.
6
FB
Feedback input for adjustable output controllers.
7
COMP
Thi s i s the output of the i nternal error ampli fi er and i nput of the peak current comparator. A
compensation network is connected to this pin to achieve the specified performance.
8
SYNC
This is synchronous control pin used to synchronize the internal oscillator to an external pulse
control signal. When not used, it should be connected to GND.
-
THERMAL P ad for heatsi nki ng purposes. C onnect to ground plane usi ng multi ple vi as. Not connected
PAD
internally.
 2007 Semtech Corp.
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SC4518
POWER MANAGEMENT
Block Diagram
+
+
Is
IN
ISEN
+
40m
SLOPE
COMP
FB
BST
-
+
PWM
S
EA
Q
POWER
TRANSISTOR
R
SW
Is
1V
REFERENCE
EN
UVLO
SOFT START
HICCUP
OL
GND
0.7V
SLOPE
FB
SLOPE COMP
SYNC
 2007 Semtech Corp.
OSCILLATOR
FREQUENCY
CLK
6
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SC4518
POWER MANAGEMENT
Application Information
General Overview
Enable
The SC4518 is a high frequency current mode buck PWM
regulator. It has an internal clock with fixed-frequency.
The SC4518 uses two feedback loops (voltage loop and
current loop) that control the duty cycle of the internal
power switch. The error amplifier functions like that of
the voltage mode controller. The output of the error
amplifier provides a switch current reference. This
technique effectively removes one of the double poles
in the output LC filter stage. With this, it is easier to
compensate a current mode converter for better
performance. A minimum 2.7V voltage is required to
saturate the NPN power switch when it is ON to reduce
its conduction loss.
Pulling and holding the EN pin below 0.4V activates the
shut down mode of the SC4518 which reduces the input
supply current to less than 10µA. During the shut down
mode, the switch is turned off. The SC4518 is turned on
if the EN pin is pulled high.
Oscillator
Its internal free running oscillator sets the PWM frequency
at 600kHz for the SC4518 without any external
components to program the frequency. An external clock
with a duty cycle from 20% to 80% connected to the
SYNC pin activates synchronous mode. The frequency
of the external clock can be from 750kHz to 1.2MHz.
Current Limit and Over Current Protection
UVLO
The current sense amplifier in the SC4518 monitors the
switch current during each cycle. Overcurrent protection
(OCP) is triggered when the current limit exceeds the upper
limit of 2A, detected by a voltage on COMP being greater
than about 2V. When an OCP fault is detected, the power
switch is turned off and the external COMP capacitor is
quickly discharged using an internal small signal NPN
transistor. Once the COMP voltage has fallen below
250mV, the power switch is turned off, control circuit is
held off for 50µs determined by an internal timer. When
the 50µs time is up, an internal timer prevents any
operation for 50µs, the part enters a normal startup cycle.
In the case of sustained overcurrent or dead-short, the
part will continually cycle through the retry sequence at a
rate dependent on the value of Ccomp. During start up,
the voltage on COMP rises roughly at the rate of dv/dt =
120µA/C comp . C comp is the total capacitance value
attached to COMP. Therefore, the retry time for a
sustained overcurrent can be approximately calculated
as:
Tretry = Ccomp ⋅
When the EN pin is pulled and held above 1.8V, the voltage
on Pin IN determines the operation of the SC4518. As VI
increases during power up, the internal circuit senses VI
and keeps the power transistor off until VI reaches 2.6V.
Load Current
The peak current IPEAK in the switch is internally limited.
For a specific application, the allowed load current IOMAX
will change if the input voltage drifts away from the original
design as given for continuous current mode:
IOMAX = 2 −
Where:
fs = switching frequency,
Vo = output voltage and
D = duty ratio, VO/VI
VI = input voltage.
2V
+ 50us
120uA
Figure 1 shows the voltage on COMP during a sustained
overcurrent condition.
Figure 2 shows the theoretical maximum load current
for the specific cases. In a real application, however, the
allowed maximum load current also depends on the layout
and the air cooling condition. Therefore, the maximum
load current may need to be degraded according to the
thermal situation of the application.
2V
250mV
Figure 1. Voltage on COMP for Startup and OCP
 2007 Semtech Corp.
VO ⋅ (1 − D)
2 ⋅ L ⋅ fs
7
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SC4518
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Application Information (Cont.)
The peak to peak inductor current is:
Ip −p = ∆I • IOMAX
Iomax (A)
Maximum Load Current vs Input Voltage
L=10uH
1.900
1.880
1.860
1.840
1.820
1.800
1.780
1.760
1.740
1.720
1.700
After the required inductor value is selected, the proper
selection of the core material is based on the peak
inductor current and efficiency specifications. The core
must be able to handle the peak inductor current IPEAK
without saturation and produce low core loss during the
high frequency operation.
Vo=2.5V
Vo=3.3V
Vo=5V
4
6
8
10
12
14
16
IPEAK = IOMAX +
18
Vi (V)
Inductor Selection
The factors for selecting the inductor include its cost,
efficiency, size and EMI. For a typical SC4518 application,
the inductor selection is mainly based on its value,
saturation current and DC resistance. Increasing the
inductor value will decrease the ripple level of the output
voltage while the output transient response will be
degraded. Low value inductors offer small size and fast
transient responses while they cause large ripple
currents, poor efficiencies and more output capacitance
to filter out the large ripple currents. The inductor should
be able to handle the peak current without saturating
and its copper resistance in the winding should be as low
as possible to minimize its resistive power loss. A good
trade-off among its size, loss and cost is to set the
inductor ripple current to be within 15% to 30% of the
maximum output current.
PCOPPER = I2LRMS ⋅ R WINDING
Where:
ILRMS is the RMS current in the inductor. This current can
be calculated as follows:
ILRMS = IOMAX ⋅ 1 +
1
⋅ ∆I2
3
Output Capacitor Selection
Basically there are two major factors to consider in
selecting the type and quantity of the output capacitors.
The first one is the required ESR (Equivalent Series
Resistance) which should be low enough to reduce the
output voltage deviation during load changes. The second
one is the required capacitance, which should be high
enough to hold up the output voltage. Before the SC4518
regulates the inductor current to a new value during a
load transient, the output capacitor delivers all the
additional current needed by the load. The ESR and ESL
of the output capacitor, the loop parasitic inductance
between the output capacitor and the load combined
with inductor ripple current are all major contributors to
the output voltage ripple. Surface mount ceramic
capacitors are recommended.
The inductor value can be determined according to its
operating point under its continuous mode and the
switching frequency as follows:
VO ⋅ ( VI − VO )
VI ⋅ fs ⋅ ∆I ⋅ IOMAX
Where:
fs = switching frequency,
∆I = ratio of the peak to peak inductor current to the
output load current and
VO = output voltage.
 2007 Semtech Corp.
2
The power loss for the inductor includes its core loss and
copper loss. If possible, the winding resistance should
be minimized to reduce inductor’s copper loss. The power
loss for the inductor includes its core loss and copper
loss. If possible, the winding resistance should be
minimized to reduce inductor’s copper loss. The core loss
can be found in the manufacturer’s datasheet. The
inductor’s copper loss can be estimated as follows:
Figure 2. Theoretical maximum load current curves
L=
Ip −p
8
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SC4518
POWER MANAGEMENT
Application Information (Cont.)
The required minimum capacitance for the boost
capacitor will be:
Input Capacitor Selection
The input capacitor selection is based on its ripple current
level, required capacitance and voltage rating. This
capacitor must be able to provide the ripple current by
the switching actions. For the continuous conduction
mode, the RMS value of the input capacitor current
ICIN(RMS) can be calculated from:
ICIN (RMS ) = IOMAX ⋅
Cboost =
IB
⋅ TW
VD
Where:
IB = the boost current and
VD= discharge ripple voltage.
VO ⋅ ( VI − VO )
V 2I
With fs = 600kHz, VD = 0.5V and IB =0.045A, the required
minimum capacitance for the boost capacitor is:
This current gives the capacitor’s power loss through its
RCIN(ESR) as follows:
Cboost =
IB 1
0.045
1
⋅ ⋅ Dmax =
⋅
⋅ 0.85 = 128nF
VD fs
0.5 600k
PCIN = I2 CIN(RMS ) • R CIN(ESR )
The internal driver of the switch requires a minimum 2.7V
to fully turn on that switch to reduce its conduction loss.
If the output voltage is less than 2.7V, the boost capacitor
can be connected to either the input side or an
independent supply with a decoupling capacitor. But the
Pin BST should not see a voltage higher than its maximum
rating.
The input ripple voltage mainly depends on the input
capacitor’s ESR and its capacitance for a given load, input
voltage and output voltage. Assuming that the input
current of the converter is constant, the required input
capacitance for a given voltage ripple can be calculated
by:
CIN = IOMAX ⋅
D ⋅ (1 − D)
fs ⋅ ( ∆VI − IOMAX ⋅ R CIN(ESR ) )
Freewheeling Diode Selection
This diode conducts during the switch’s off-time. The diode
should have enough current capability for full load and
short circuit conditions without any thermal concerns.
Its maximum repetitive reverse block voltage has to be
higher than the input voltage of the SC4518. A low
forward conduction drop is also required to increase the
overall efficiency. The freewheeling diode should be
turned on and off fast with minimum reverse recovery
because the SC4518 is designed for high frequency
applications. SS23 Schottky rectifier is recommended
for certain applications. The average current of the diode,
ID_AVG can be calculated by:
Where:
∆VI = the given input voltage ripple.
Because the input capacitor is exposed to the large surge
current, attention is needed for the input capacitor. If
tantalum capacitors are used at the input side of the
converter, one needs to ensure that the RMS and surge
ratings are not exceeded. For generic tantalum
capacitors, it is suggested to derate their voltage ratings
at a ratio of about two to protect these input capacitors.
Boost Capacitor and its Supply Source Selection
The boost capacitor selection is based on its discharge
ripple voltage, worst case conduction time and boost
current. The worst case conduction time Tw can be
estimated as follows:
TW =
ID _ AVG = IO max ⋅ (1 − D)
Thermal Considerations
There are three major power dissipation sources for the
SC4518. The internal switch conduction loss, its switching
loss due to the high frequency switching actions and the
base drive boost circuit loss. These losses can be
estimated as:
1
⋅ Dmax
fs
Where:
fs = the switching frequency and
Dmax = maximum duty ratio, 0.85 for the SC4518.
2
Ptotal = Io ⋅ Ron ⋅ D + 11.25 ⋅ 10 −3 ⋅ Io ⋅ VI +
 2007 Semtech Corp.
9
10
⋅ Io ⋅ D ⋅ ( Vboost )
500
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SC4518
POWER MANAGEMENT
Application Information (Cont.)
Where:
IO = load current;
R = on-equivalent resistance of the switch;
ON
VBOOST = input voltage or output based on the boost circuit
connection.
The goal of the compensation design is to shape the loop
to have a high DC gain, high bandwidth, enough phase
margin, and high attenuation for high frequency noises.
Figure 3 gives a typical compensation network which
offers 2 poles and 1 zero to the power stage:
TJ = TA + θJA ⋅ Ptotal
5
8
EN
SYNC
COMP
6
Vout
C
R1
7
R2
R3
D2
Figure 3. Compensation network provides 2 poles and 1
zero.
The compensation network gives the following
characteristics:
Loop Compensation Design
s
ωZ
R2
⋅ gm ⋅
GCOMP (s) = ω1 ⋅
s
R1 + R 2
s ⋅ (1 +
)
ωP 2
1+
The SC4518 has an internal error amplifier and requires
a compensation network to connect between the COMP
pin and GND pin as shown in Figure 3. The compensation
network includes C4, C5 and R3. R1 and R2 are used to
program the output voltage according to:
Where:
R1
)
R2
Assuming the power stage ESR (equivalent series
resistance) zero is an order of magnitude higher than
the closed loop bandwidth, which is typically one tenth of
the switching frequency, the power stage control to output
transfer function with the current loop closed (Ridley
model) for the SC4518 will be as follows:
ω1 =
1
C 4 + C5
ωZ =
1
R3 ⋅ C4
ωP 2 =
2.5 ⋅ R L
s
1+
1
RL ⋅ C
C 4 + C5
R 3 ⋅ C 4 ⋅ C5
The loop gain will be given by:
R
R2
1
T(s) = GCOMP (s) ⋅ G VD (s) = 2.125 ⋅ 10 − 3 ⋅ L ⋅
⋅
C 4 R1 + R 2 s
Where:
RL – Load and
C – Output capacitor.
 2007 Semtech Corp.
FB
L1
3
C4
Pdiode = VF ⋅ Io ⋅ (1 − D)
G VD (s) =
SW
C5
The freewheeling diode also contributes a significant
portion of the total converter loss. This loss should be
minimized to increase the converter efficiency by using
Schottky diodes with low forward drop (VF).
VO = 1.2 • (1 +
SC4518
4
θ JA is the thermal resistance from junction to ambient.
Its value is a function of the IC package, the application
layout and the air cooling system.
IN
GND
2
BST
1
The junction temperature of the SC4518 can be
further decided by:
10
1+
(1 +
s
ωZ
s
s
) ⋅ (1 +
)
ωP1
ωP 2
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SC4518
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Application Information (Cont.)
Layout Guidelines:
Where:
ωp1 =
1
RL ⋅ C
In order to achieve optimal electrical and thermal
performance for high frequency converters, special
attention must be paid to the PCB layouts. The goal of
layout optimization is to identify the high di/dt loops and
minimize them. The following guidelines should be used
to ensure proper operation of the converters.
One integrator is added at origin to increase the DC gain.
ωZ is used to cancel the power stage pole ωP1 so that the
loop gain has –20dB/dec rate when it reaches 0dB line.
ωP2 is placed at half switching frequency to reject high
frequency switching noises. Figure 4 gives the asymptotic
diagrams of the power stage with current loop closed
and its loop gain.
1. A ground plane is suggested to minimize switching
noises and trace losses and maximize heat
transferring.
2. Start the PCB layout by placing the power components
first. Arrange the power circuit to achieve a clean
power flow route. Put all power connections on one
side of the PCB with wide copper filled areas if
possible.
3. The VIN bypass capacitor should be placed next to
the VIN and GND pins.
4. The trace connecting the feedback resistors to the
output should be short, direct and far away from any
noise sources such as switching node and switching
components.
5. Minimize the loop including input capacitor, the
SC4518 and freewheeling diode D2. This loop passes
high di/dt current. Make sure the trace width is wide
enough to reduce copper losses in this loop.
6. Maximize the trace width of the loop connecting the
inductor, freewheeling diode D 2 and the output
capacitor.
7. Connect the ground of the feedback divider and the
compensation components directly to the GND pin
of the SC4518 by using a separate ground trace.
8. Connect Pin 4 to a large copper area to remove the
IC heat and increase the power capability of the
SC4518. A few feedthrough holes are required to
connect this large copper area to a ground plane to
further improve the thermal environment of the
SC4518. The traces attached to other pins should
be as wide as possible for the same purpose.
MAG
Loop gain T(s)
ωp1
Power stage
ωC
ωP2
ω
ωZ
Figure 4. Asymptotic diagrams of power stage with
current loop closed and its loop gain.
The design guidelines for the SC4518 applications are
as following:
1. Set the loop gain crossover corner frequency ω C
for given switching corner frequency ωC = 2πf .
c
2. Place an integrator at the origin to increase DC and
low frequency gains.
3. Select ωZ such that it is placed at ωP1 to obtain a
-20dB/dec rate to go across the 0dB line.
4. Place a high frequency compensator pole
ωP2 (ωP2 = πfs) to get the maximum attenuation of
the switching ripple and high frequency noise with
the adequate phase lag at ωC.
 2007 Semtech Corp.
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SC4518
POWER MANAGEMENT
Application Information (Cont.)
Design Example 1. 12V to 5V.
D3
C1
0.22u
1
VI =12V
4.75k
5
R4
EN
SYNC
Vo=5V
3
SW
10uH
6
FB
4
8
L1
BST
C3
10u
IN
GND
2
R1
31.6k
C2
47u
7
COMP
SC4518
C4
6.8n
C5
180p
R3
8.06k
R2
10k
D2
Bill of Materials
Item
Qty
Reference
Value
Part No./Manufacturer
1
1
C1
0.22uF, 25V, X7R, 0805
Vishay P/N: VJ0805Y224KXX
2
1
C2
47uF, 6.3V, 1210
Murata
3
1
C3
10uF, 25V, 1210
Panasonic
4
1
C4
6.8nF, 25V, 0805
Vishay
5
1
C5
180pF, 50V, 0805
Vishay
6
1
D3
1N4148WS, SOD-323
7
1
D2
S S 23
Fairchild P/N: SS23
8
1
L1
10uH
Cooper P/N: DR74-100
9
1
R1
31.6k, 1%, 0805
SMTZONE
10
1
R2
10k, 1%. 0805
SMTZONE
11
1
R3
8.06k, 0805
SMTZONE
12
1
R4
4.75k, 0805
SMTZONE
13
1
U1
S C 4518
Semtech P/N: SC4518ISTRT
Unless specified, all resistors have 1% precision with 0603 package.
Resistors are +/-1% and all capacitors are +/-20%
 2007 Semtech Corp.
12
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SC4518
POWER MANAGEMENT
Application Information (Cont.)
(COMPONENT - BOTTOM)
(COMPONENT - TOP)
SC4518
8
(PCB - TOP)
 2007 Semtech Corp.
(PCB - BOTTOM)
13
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SC4518
POWER MANAGEMENT
Outline Drawing - SOIC-8L EDP
A
D
e
N
DIMENSIONS
INCHES
MILLIMETERS
DIM
MIN NOM MAX MIN NOM MAX
2X E/2
E1 E
1
2
ccc C
2X N/2 TIPS
e/2
B
D
aaa C
SEATING
PLANE
A2 A
C
A1
bxN
bbb
.053
.069
.000
.005
.049
.065
.020
.012
.007
.010
.189 .193 .197
.150 .154 .157
.236 BSC
.050 BSC
.116 .120 .130
.085 .095 .099
.010
.020
.016 .028 .041
(.041)
8
0°
8°
.004
.010
.008
A
A1
A2
b
c
D
E1
E
e
F
H
h
L
L1
N
01
aaa
bbb
ccc
C A-B D
1.35
1.75
0.00
0.13
1.25
1.65
0.31
0.51
0.17
0.25
4.80 4.90 5.00
3.80 3.90 4.00
6.00 BSC
1.27 BSC
2.95 3.05 3.30
2.15 2.41 2.51
0.25
0.50
0.40 0.72 1.04
(1.05)
8
0°
8°
0.10
0.25
0.20
h
F
EXPOSED PAD
h
H
H
c
GAGE
PLANE
0.25
L
(L1)
SEE DETAIL
A
DETAIL
01
A
SIDE VIEW
NOTES:
1.
CONTROLLING DIMENSIONS ARE IN MILLIMETERS (ANGLES IN DEGREES).
2.
DATUMS -A- AND
3.
DIMENSIONS "E1" AND "D" DO NOT INCLUDE MOLD FLASH, PROTRUSIONS
OR GATE BURRS.
REFERENCE JEDEC STD MS-012, VARIATION BA.
4.
 2007 Semtech Corp.
-B- TO BE DETERMINED AT DATUM PLANE
14
-H-
www.semtech.com
SC4518
POWER MANAGEMENT
Land Pattern - SOIC-8L-EDP
E
SOLDER MASK
D
DIM
(C)
G
F
C
D
E
F
G
P
X
Y
Z
Z
Y
THERMAL VIA
Ø 0.36mm
P
X
DIMENSIONS
INCHES
MILLIMETERS
(.205)
.134
.201
.101
.118
.050
.024
.087
.291
(5.20)
3.40
5.10
2.56
3.00
1.27
0.60
2.20
7.40
NOTES:
1.
THIS LAND PATTERN IS FOR REFERENCE PURPOSES ONLY.
CONSULT YOUR MANUFACTURING GROUP TO ENSURE YOUR
COMPANY'S MANUFACTURING GUIDELINES ARE MET.
2. REFERENCE IPC-SM-782A, RLP NO. 300A.
3.
THERMAL VIAS IN THE LAND PATTERN OF THE EXPOSED PAD
SHALL BE CONNECTED TO A SYSTEM GROUND PLANE.
FAILURE TO DO SO MAY COMPROMISE THE THERMAL AND/OR
FUNCTIONAL PERFORMANCE OF THE DEVICE.
Contact Information
Semtech Corporation
Power Management Products Division
200 Flynn Road, Camarillo, CA 93012
Phone: (805)498-2111 FAX (805)498-3804
 2007 Semtech Corp.
15
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