1
DEMO MANUAL DC195
NO-DESIGN SWITCHER
LTC1627 Monolithic
Synchronous Step-Down Regulator
D
U
ESCRIPTIO
, LTC and LT are registered trademarks of Linear Technology Corporation.
W
ARY
A
U
CE SUPERFOR
WW
SYMBOL PARAMETER CONDITIONS JUMPER POSITION VALUE
V
IN
Input Voltage Range JP1 = “≥ 5V” 2.65V to 8.5V
JP1 = “< 5V” 2.65V to 4.5V
V
OUT
Output Voltage See Figure 2 JP2 = “1.8V” 1.82V ± 0.043V
JP2 = “2.5V” 2.52V ± 0.06V
JP2 = “2.9V” 2.94V ± 0.07V
JP2 = “3.3V” 3.33V ± 0.079V
JP2 = “OPEN” Note 1
I
Q
Forced Continuous Supply Current V
IN
= 5V, SYNC/FCB = 0V, RUN/SS = 2V, I
OUT
= 0mA JP1 = “≥ 5V,” JP2 = “3.3V” 3.5mA
Burst ModeTM Enabled Supply Current V
IN
= 5V, SYNC/FCB = 2V, RUN/SS = 2V, I
OUT
= 0mA JP1 = “≥ 5V,” JP2 = “3.3V” 200µA
Shutdown Current V
IN
= 5V, RUN/SS = 0V, I
OUT
= 0mA JP1 = “≥ 5V,” JP2 = “3.3V” 15µA
Demonstration circuit DC195 is a constant-frequency
step-down converter using an LTC
®
1627 monolithic syn-
chronous regulator. It provides low input voltage, high
efficiency conversion for cell phones and other portable
electronics operating from one or two Li-Ion cells or three
to six NiCd cells. Constant 350kHz operation and up to
500mA output capability in an SO-8 package provide a low
noise, space-efficient solution for wireless applications.
The circuit highlights the capability of the the LTC1627.
Designed to work at low voltages, the input voltage (V
IN
)
can range from 2.65V to 8.5V. At input voltages lower than Burst Mode is a trademark of Linear Technology Corporation.
4.5V, a charge pump bootstrapped to the SW node can be
enabled via a jumper to produce a negative supply. This
supply is used by the top driver to increase the gate
overdrive of the top P-channel MOSFET, lowering its
R
DS(ON)
and increasing efficiency. At V
IN
< 2.5V, the
LTC1627 shuts down and draws just a few microamperes,
making it ideal for single lithium-ion battery applications.
The output voltage is programmable from 1.8V to 3.3V via
a second jumper.
UW
AT
Y
P
I
CALPER
F
O
RC
ECCHARA TERISTIC
U
AD
BOARD PH TOO
S
S
LOAD CURRENT (mA)
1 10 100 1000
EFFICIENCY (%)
195 TPC01
100
90
80
70
60
VIN = 3.6V
VOUT = 2.5V
JP1 = “≥ 5V”
JP1 = “< 5V”
LOAD CURRENT (mA)
1 10 100 1000
EFFICIENCY (%)
195 TPC02
100
90
80
70
60
VOUT = 3.3V
JP1 = “≥ 5V”
VIN = 5V
VIN = 8.5V
LTC1627 Efficiency Curve LTC1627 Efficiency Curve Demo Board
2
DEMO MANUAL DC195
NO-DESIGN SWITCHER
D
U
ESCRIPTIO
At low output currents, the LTC1627 automatically switches
to Burst Mode
operation to reduce switching losses and
maintain high operating efficiencies. In switching-noise
sensitive applications, Burst Mode
operation can be inhib-
ited by grounding the SYNC/FCB pin or synchronizing it
with an external clock. Gerber files for this circuit board
are available. Call the LTC factory.
W
ARY
A
U
CE SUPERFOR
WW
SYMBOL PARAMETER CONDITIONS JUMPER POSITION VALUE
I
OUT
Minimum Output Current V
IN
= 5V, V
OUT
= 3.3V JP1= “≥ 5V” 500mA
V
IN
= 3V, V
OUT
= 2.5V JP1= “< 5V” 500mA
f
OSC
Operating Frequency Unsynchronized All 350kHz
Synchronized All 385kHz to 525kHz
V
RIPPLE
Typical Output Ripple I
OUT
= 500mA, V
IN
= 5V, V
OUT
= 3.3V JP1= “≥ 5V” 30mV
P-P
V
OUT
Typical Load Regulation 0mA < I
OUT
< 0.5A, V
IN
= 5V, V
OUT
= 3.3V JP1= “≥ 5V” 0.5%
V
FCB
Forced Continuous Threshold Voltage All 0.8V
V
SYNC
Synchronize Threshold Voltage All 1.2V
V
RUN/SS
Minimum Shutdown Threshold Voltage All 0.4V
Note 1: Programmable via optional R5. V
OUT
= 0.8V(1 + 210k/R5)
LTC1627CS8
1
2
3
4
8
7
6
5
TOP VIEW
SYNC/FCB
V
DR
V
IN
SW
I
TH
RUN/SS
V
FB
GND
S8 PACKAGE
8-LEAD PLASTIC SO
Figure 1. LTC1627 Constant Frequency, High Efficiency Converter
V
FB
GND
I
TH
V
IN
SW
3
4
1
6
5
I
TH
SYNC/FCB
RUN/SS
2
8
V
DR
7
LTC1627
C
C1
C
SS
, 0.1µF
C4
47pF
R
C
E2
RUN/SS D1
BAT54S
C1
0.1µF
JP1
V
IN
< 5V JP1
V
IN
≥ 5V
R1
165k
C2
0.1µF
C3
0.1µF
C
IN
22µF
16V
+
+
L1, 10µH
D2*
10V
C
OUT
100µF
6.3V
1.8V
R2
97.6k
2.5V
R3
78.7k
R7
10Ω
JP2
2.9V
R4
66.5k R5**
OPTIONAL
3.3V OPEN
R6
210k
E1
SYNC/FCB
E6
V
IN
≤ 8.5V
E5
V
OUT
E4
V
OSENSE
E3/E7
GND
DC195 • SCHEMATIC
D2 IS FOR PROTECTION AGAINST MISAPPLIED INPUT VOLTAGES WITH JP1 IN THE "< 5V" POSITION.
SPACE IS PROVIDED FOR AN OPTIONAL RESISTOR TO PROGRAM A CUSTOM OUTPUT VOLTAGE. THE OUTPUT VOLTAGE MUST NOT EXCEED 3.3V.
OPTIONAL
*
**
PACKAGE A D SCHE ATIC DIAGRA S
W UW
3
DEMO MANUAL DC195
NO-DESIGN SWITCHER
REFERENCE
DESIGNATOR QUANTITY PART NUMBER DESCRIPTION VENDOR TELEPHONE
CIN 1 TPSC226M016R0375 22µF 16V TPS Tantalum Capacitor AVX (803) 448-9411
COUT 1 TPSC107M006R0150 100µF 6V TPS Tantalum Capacitor AVX (803) 448-9411
C1, C2, C3, CSS 4 0603YC104KAT 0.1µF 16V X7R Chip Capacitor AVX (803) 946-0362
C4 1 06035A470JAT 47pF 50V NPO Chip Capacitor AVX (803) 946-0362
CC1 Optional
D1 1 BAT54S Dual Schottky Diode in SOT-23 Zetex (516) 543-7100
E1 to E6 6 2501-2 Turret, Testpoint Mill-Max (516) 922-6000
JP1 1 3914-04-G2 0.05" Double Row Header COMM CON (818) 301-4200
JP2 1 3914-10-G2 0.05" Double Row Header COMM CON (818) 301-4200
JP1, JP2 2 50633-R 0.05" Center Shunt COMM CON (818) 301-4200
L1 1 CD54-150MC 15µH 20% Inductor Sumida (847) 956-0666
D2 1 MMBZ5240B 10V Zener Diode in SOT-23 Motorola (602) 244-3576
R1 1 CR16-1653FM 165k 1% 1/16W Chip Resistor TAD (800) 508-1521
R2 1 CR16-9762FM 97.6k 1% 1/16W Chip Resistor TAD (800) 508-1521
R3 1 CR16-7872FM 78.7k 1% 1/16W Chip Resistor TAD (800) 508-1521
R4 1 CR16-6652FM 66.5k 1% 1/16W Chip Resistor TAD (800) 508-1521
R6 1 CR16-2103FM 210k 1% 1/16W Chip Resistor TAD (800) 508-1521
R7 1 CR16-100JM 10Ω 5% 1/16W Chip Resistor TAD (800) 508-1521
R5 Optional
RCOptional
U1 1 LTC1627CS8 Monolithic Synchronous Step-Down Regulator LTC (408) 432-1900
PARTS LIST
4
DEMO MANUAL DC195
NO-DESIGN SWITCHER
QUICK START GUIDE
This demonstration board is easily set up to evaluate the
performance of the LTC1627 IC. Please follow the proce-
dure outlined below for proper operation.
• Refer to Figure 6 for proper connection of monitoring
equipment to ensure correct measurement.
• Connect the input power supply to the VIN and GND
terminals on the left-hand side of the board. Do not
increase VIN over 10V or the Zener, D2, will be
damaged. Select the appropriate position of jumper
JP1 for the VIN voltage (position “VIN <5V” for VIN
<4.5V only).
• Connect the load between the VOUT and GND
terminals on the right side of the board.
• The RUN/SS pin can be left unconnected. To shut
down the LTC1627, tie this pin to GND.
• Set the desired output voltage with jumper JP2, as
shown in Figure 2 and Table 1.
Table 1. Maximum Allowable Input Voltage vs Selected
Output Voltage and JP1 Position
MAXIMUM V
IN
FOR JP1 POSITION
“≥ 5V” “< 5V” (Note 1)
1.8V 8.5V 4.5V
2.5V 8.5V 4.5V
2.9V 8.5V 4.5V
3.3V 8.5V 4.5V
N/A
JP2 OUTPUT VOLTAGE
Note 1: The silkscreen label “<5V” on the demo board is a simplified
notation. The actual voltage should be ≤4.25V.
OPERATIO
U
The circuit in Figure 1 highlights the capabilities of the
LTC1627. The application circuit is set up for a variety of
output voltages. Output voltages from 1.8V to 3.3V or user
programmable voltages can be obtained by selecting the
appropriate jumper position.
The LTC1627 is a monolithic synchronous step-down
switching regulator using a fixed-frequency architecture.
Burst Mode operation provides high efficiency at low load
currents. Operating efficiencies typically exceed 90% over
two decades of load current range. 100% duty cycle
provides low dropout operation, which extends operating
time in battery-operated systems.
Do not use small spring-clip leads when testing this
circuit. Small spring-clip leads are very convenient for
small-signal bench testing and voltage measurements,
but should not be used with this circuit. Soldered wire
connections are required to properly ascertain the perfor-
mance of the PC board.
This demonstration board is intended for the evaluation of
the LTC1627 switching regulator IC and was not designed
for any other purpose.
The operating frequency of this demo circuit is 350kHz,
the frequency of the LTC1627’s internal oscillator. For
higher frequencies, SYNC/FCB (E1) can be synchronized
with an external clock. Burst Mode operation is automati-
cally disabled when the SYNC/FCB pin is externally driven.
Grounding SYNC/FCB also disables Burst Mode opera-
tion, potentially reducing noise and interference.
Soft start is provided by an external capacitor, C
SS
, which
can be used to properly sequence supplies. The maximum
operating current level is 0.5A.
This demo board is optimized for 3.3V outputs and 5V
input. Output voltages from 1.8V to 3.3V are available by
selecting the appropriate jumper position of JP2. For other
output voltages, select the OPEN (E) position and add an
1.8V 2.5V 2.9V 3.3V OPEN
JP2
DC195 • F02
Figure 2. Output Voltage Selection (JP2)
(3.3V Position Shown)
5
DEMO MANUAL DC195
NO-DESIGN SWITCHER
OPERATIO
U
OSC
BURST
DEFEAT
+
–
SLOPE
COMP
V
IN
V
IN
Y
X
0.6V
8
3
SYNC/FCB
V
FB
–
+
+
–
+
–
0.8V
0.86V
+
–
0.8V
EA
I
TH
1
V
IN
2.25µA
RUN/SS 2
OVDET
FCB
–
+
I
RCMP
SWITCHING
LOGIC
AND
BLANKING
CIRCUIT
+
–
0.12V
SHUTDOWN
EN
BURST
SLEEP
S
R
Q
Q
V
IN
V
IN
0.4V
–+
I
COMP
6Ω
SW
GND
5
V
DR
7
V
IN
6
4
0.8V
REFERENCE
UVLO
TRIP = 2.5V
RUN/
SOFT START
FREQUENCY
SHIFT
ANTI
SHOOT THRU
DC195 • FD
Y = “0” WHEN X IS A CONSTANT “1”
1.5µA
Figure 3. Functional Block Diagram
appropriate resistor value in the space provided. The
output voltage must never exceed 3.3V because the output
capacitor may be damaged. The input supply can range
from 2.65V to 8.5V.
Main Control Loop (Refer to Functional Diagram)
The LTC1627 uses a constant-frequency, current mode
step-down architecture. Both the main and synchronous
switches, consisting of top P-channel and bottom
N-channel power MOSFETs, are internal. During normal
operation, the internal top power MOSFET is turned on
during each cycle when the oscillator sets the RS latch,
and turned off when the current comparator, I
COMP
, resets
the RS latch. The peak inductor current at which I
COMP
resets the RS latch is controlled by the voltage on the I
TH
pin, which is the output of error amplifier EA. The V
FB
pin
allows EA to receive an output feedback voltage from an
external resistive divider. When the load current increases,
it causes a slight decrease in the feedback voltage relative
to the 0.8V reference, which, in turn, causes the I
TH
voltage
to increase until the average inductor current matches the
new load current. While the top MOSFET is off, the bottom
6
DEMO MANUAL DC195
NO-DESIGN SWITCHER
OPERATIO
U
MOSFET is turned on until either the inductor current
starts to reverse, as indicated by the current reversal
comparator I
RCMP
, or the next cycle begins.
The main control loop is shut down by pulling the RUN/SS
pin low. Releasing RUN/SS allows an internal 2.25µA
current source to charge soft start capacitor C
SS
. When
C
SS
reaches 0.7V, the main control loop is enabled with
the I
TH
voltage clamped at approximately 5% of its maxi-
mum value. As C
SS
continues to charge, I
TH
is gradually
released, allowing normal operation to resume.
Comparator OVDET guards against transient overshoots
> 7.5% by turning the main switch off and turning the
synchronous switch on. With the synchronous switch
turned on, the output is crowbarred. This may cause a
large amount of current to flow from V
IN
if the main switch
is damaged, blowing the system fuse.
SYNC/FCB Pin Function (Frequency Synchronization
and Burst Mode Disable)
The LTC1627 can be synchronized with an external
TTL/CMOS-compatible clock signal driving the SYNC/FCB
pin (E1). The frequency range of this signal must be from
385kHz to 525kHz. DO NOT attempt to synchronize the
LTC1627 below 385kHz as this may cause abnormal
operation and an undesired frequency spectrum. The top
MOSFET turn-on follows the rising edge of the external
source.
When the LTC1627 is clocked by an external source, Burst
Mode operation is disabled; the LTC1627 then operates in
PWM pulse-skipping mode. In this mode, when the output
load is very low, current comparator I
COMP
remains tripped
for more than one cycle and forces the main switch to stay
off for the same number of cycles. Increasing the output
load slightly allows constant-frequency PWM operation to
resume.
Frequency synchronization is inhibited when the feedback
voltage, V
FB
, is below 0.6V. This prevents the external
clock from interfering with the frequency foldback for
short-circuit protection.
The LTC1627 is capable of Burst Mode operation, in which
the internal power MOSFETs operate intermittently based
on load demand. To enable Burst Mode, simply allow the
SYNC/FCB pin to float or connect it to a logic high. To
disable Burst Mode operation and enable forced continu-
ous mode (continuous switching even at no load), connect
the SYNC/FCB pin to GND. The threshold voltage between
Burst Mode and forced continuous mode is 0.8V. This
provides a means to regulate a flyback winding output. See
the LTC1627 data sheet for additional information.
Figure 4. Using a Charge Pump to Bias VDR
V
DR
V
IN
SW
LTC1627
C2
0.1µF
D1
D2
L1
C1
0.1µF
C
OUT
100µF
V
OUT
V
IN
< 4.25V
DC195 • F03
+
7
DEMO MANUAL DC195
NO-DESIGN SWITCHER
OPERATIO
U
When the converter uses Burst Mode operation, the peak
current of the inductor is set to approximately 200mA,
even though the voltage at the I
TH
pin indicates a lower
value. The voltage at the I
TH
pin drops when the inductor’s
average current is greater than the load requirement. As
the I
TH
voltage drops below 0.12V, the BURST comparator
trips, causing the internal sleep line to go high and turn off
both power MOSFETs.
In sleep mode, both power MOSFETs are held off and the
internal circuitry is partially turned off, reducing the quies-
cent current to 200µA. The load current is now supplied
from the output capacitor. When the output voltage drops,
causing I
TH
to rise above 0.22V, the top MOSFET is again
turned on and this process repeats.
SHORT-CIRCUIT PROTECTION
When the output is shorted to ground, the frequency of the
oscillator is reduced to about 35kHz, 1/10 of the nominal
frequency. This frequency foldback ensures that the
inductor current has more time to decay, thereby prevent-
ing runaway. The oscillator's frequency will gradually
increase to 350kHz (or the synchronized frequency) when
V
FB
rises above 0.3V.
DROPOUT OPERATION
When the input supply voltage decreases toward the
output voltage, the duty cycle increases toward the maxi-
mum on-time. Further reduction of the supply voltage
forces the main switch to remain on for more than one
cycle until it reaches 100% duty cycle. The output voltage
will then be determined by the input voltage minus the voltage
drop across the P-channel MOSFET and the inductor. In
Burst Mode operation or pulse skipping mode operation
(externally synchronized) with the outputs lightly loaded,
the LTC1627 transistions through continuous mode as it
enters dropout.
UNDERVOLTAGE LOCKOUT
A precision undervoltage lockout shuts down the LTC1627
when V
IN
drops below 2.5V, making it ideal for single
lithium-ion battery applications. In shutdown, the LTC1627
draws only several microamperes, which is low enough to
prevent deep discharge and possible damage to a lithium-
ion battery nearing its end of charge. A 150mV hysteresis
ensures reliable operation with noisy supplies.
LOW SUPPLY OPERATION
The LTC1627 is designed to operate down to 2.65V supply
voltage. At this voltage the converter is most likely to be
running at high duty cycles or in dropout, where the main
switch is on continuously. Hence, the I
2
R loss is due mainly
to the R
DS(ON)
of the P-channel MOSFET. See the LTC1627
data sheet for additional information.
When V
IN
is low (< 4.5V), the R
DS(ON)
of the P-channel
MOSFET can be lowered by driving its gate below ground.
The top P-channel MOSFET driver makes use of a floating
return pin, V
DR
, to allow biasing below GND. A simple charge
pump bootstrapped to the SW pin realizes a negative
voltage at the V
DR
pin, as shown in Figure 4. This charge
pump can be enabled via jumper JP1 for V
IN
<4.5V. For
V
IN
≥ 4.5V, do not enable the charge pump to ensure that
V
IN
– V
DR
does not exceed its absolute maximum voltage.
A 10V Zener clamp (Z3) prevents V
IN
– V
DR
from exceed-
ing 10V even if V
IN
≥ 5V is inadvertently applied.
When V
IN
decreases to a voltage close to V
OUT
, the loop
may enter dropout and attempt to turn on the P-channel
MOSFET continuously. When the V
DR
charge pump is
enabled, a dropout detector counts the number of oscilla-
tor cycles that the P-channel MOSFET remains on and
periodically forces a brief off period to allow C1 to
recharge. 100% duty cycle is allowed when V
DR
is
grounded.
SLOPE COMPENSATION AND PEAK INDUCTOR
CURRENT
Slope compensation provides stability by preventing
subharmonic oscillations. It works by internally adding a
ramp to the inductor current signal at duty cycles in excess
of 40%. As a result, the maximum inductor peak current
is lower for V
OUT
/V
IN
> 0.4 than when V
OUT
/V
IN
< 0.4. See
the maximum inductor peak current vs duty cycle graph in
Figure 5.
8
DEMO MANUAL DC195
NO-DESIGN SWITCHER
OPERATIO
U
The graph labeled “With External Clock” shows the worst-
case peak current reduction obtained when the oscillator
is synchronized at its minimum frequency, that is, to a
clock just above the oscillator’s free-running frequency.
HOW TO MEASURE VOLTAGE REGULATION
When trying to measure voltage regulation, remember
that all measurements must be taken at the point of
regulation. This point is where the LTC1627’s control loop
looks for the information to keep the output voltage
constant. In this demonstration board, this information
point occurs between Pin 4, the GND of the LTC1627, and
the output side of R6. These points correspond to the GND
(E7) and V
OSENSE
(E4) terminals of the board. Output
voltage test leads should be attached directly to these
terminals. The load should be placed between V
OUT
(E5)
and GND (E7). Measurements
should not
be taken at the
end of test leads at the load. Refer to Figure 6 for the proper
monitoring equipment configuration.
This applies to line regulation (input-to-output voltage
regulation) as well as load regulation tests. In doing the
line regulation tests, always look at the input voltage
across the input terminals.
Figure 5. Maximum Inductor Peak Current Vs Duty Cycle
MONOLITHIC SYNCHRONOUS
STEP-DOWN REGULATOR
LTC1627CS8
+
V
IN
SYNC/FCB
RUN/SS
GND
E6
E1
E2
E3
V
OUT
V
OSENSE
GND
E5
E4
E7
+
V
IN
A
+
V
+
V
I
IN
+
A
I
OUT
V
OUT
1.8V
2.5V
2.9V
3.3V
OPEN
JP2
JP1
V
IN
< 5V
V
IN
≥ 5V
LOAD
DEMO CIRCUIT DC195
(408) 432-1900
DC195 • F05
10Ω
Figure 6. Proper Measurement Setup
DUTY CYCLE (%)
0
MAXIMUM INDUCTOR PEAK CURRENT (mA)
950
900
850
800
750
700
650
600
550
500 80
DC195 • F04
20 40 60 100
WITH
EXTERNAL
CLOCK
WITHOUT
EXTERNAL
CLOCK
9
DEMO MANUAL DC195
NO-DESIGN SWITCHER
OPERATIO
U
For the purposes of these tests, the demonstration circuit
should be powered from a regulated DC bench supply, so
that variations on the DC input do not add errors to the
regulation measurements.
REMOTE OUTPUT-VOLTAGE SENSING
Remote output-voltage sensing can be accomplished by
modifying the PC board. A small PC trace connecting V
OUT
to V
OSENSE
must be cut, as shown in Figure 7. An external
connection from V
OSENSE
directly to the load must be
made. To prevent uncertainty, there is a 10Ω resistor
placed across the V
OUT
and V
OSENSE
terminals. Never,
under any circumstance, allow V
OSENSE
to float!
RUN/SOFT START FUNCTION
The RUN/SS pin (E2) is a dual-purpose pin that provides
the soft start function and a means to shut down the
LTC1627. Soft start reduces surge currents from V
IN
by
gradually increasing the internal current limit. Power
supply sequencing can also be accomplished using this
pin.
An internal 2.25µA current source charges an external
capacitor, C
SS
. When the voltage on RUN/SS reaches
0.7V, the LTC1627 begins operating. As the voltage on
RUN/SS continues to increase from 0.7V to 1.8V, the
internal current limit also increases at a proportional linear
rate. The current limit begins at 25mA (at V
RUN/SS
≤0.7V)
and ends at the Figure 5 value (V
RUN/SS
≥ 1.8V). The output
current thus increases slowly, charging the output capaci-
tor. If RUN/SS has been pulled all the way to ground, there
is a delay before starting of approximately 310ms/µF,
followed by an additional 490ms/µF to reach full current.
C
SS
= 0.1µF on this PC board.
Pulling the RUN/SS pin below 0.7V (0.4V min) puts the
LTC1627 into a low quiescent current shutdown mode
(I
Q
< 15µA). See the LTC1627 data sheet for further
information.
COMPONENT MANUFACTURERS
Table 2 is a partial list of manufacturers of components
that can be used in LTC1627 applications. Using compo-
nents other than the ones supplied on the demonstration
board will require careful analysis to verify that all compo-
nent specifications are not exceeded. Finally,
recharacterizing the circuit for efficiency is necessary.
Figure 7. Remote Output Voltage Sense
MONOLITHIC SYNCHRONOUS
STEP-DOWN REGULATOR
LTC1627CS8
+
V
IN
SYNC/FCB
RUN/SS
GND
E6
E1
E2
E3
V
OUT
V
OSENSE
GND
E5
E4
E7
+
V
IN
A
+
V
+
V
I
IN
+
A
I
OUT
V
OUT
1.8V
2.5V
2.9V
3.3V
OPEN
JP2
JP1
V
IN
< 5V
V
IN
≥ 5V
LOAD
DEMO CIRCUIT DC195
(408) 432-1900
DC195 • F06
CUT
THIS TRACE
10Ω
10
DEMO MANUAL DC195
NO-DESIGN SWITCHER
Table 2. List of Alternative Component Manufacturers
MANUFACTURER DEVICE PHONE FAX
AVX Capacitors (803) 448-9411 (803) 448-1943
Central Semiconductor Diodes (516) 435-1110 (516) 435-1824
Coilcraft Inductors (847) 639-6400 (847) 639-1469
Coiltronics Inductors (561) 241-7876 (561) 241-9339
COMM CON Connectors (818) 301-4200 (818) 301-4212
Dale Inductors (605) 665-9301 (605) 665-0817
International Rectifier Diodes (310) 322-3331 (310) 322-3332
Motorola Diodes (602) 244-3576 (602) 244-4015
Murata-Erie Capacitors (814) 237-1431 (814) 238-0490
Sanyo Capacitors (619) 661-6835 (619) 661-1055
(81) 0952-82-3959 (81) 0952-82-4655
Sprague Capacitors (603) 224-1961 (603) 224-1430
Sumida Inductors (847) 956-0666 (847) 956-0702
(81) 03-3607-5111 (81) 03-3607-5114
TDK Inductors (847) 803-6100 (847) 803-6294
TAD Resistors (714) 255-9123 (714) 255-9291
Zetex Diodes (516) 543-7100 (516) 864-7630
OPERATIO
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11
DEMO MANUAL DC195
NO-DESIGN SWITCHER
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen-
tation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
W
PCB LAYOUT A
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D FIL
Component Side Silkscreen Component Side
Component Side Solder Mask Solder Side
Solder Side Solder MaskPastemask
12
DEMO MANUAL DC195
NO-DESIGN SWITCHER
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900
●
FAX: (408) 434-0507
●
www.linear-tech.com
LINEAR TE CHNO LOGY CO RP O R ATIO N 1998
dc195f LT/TP 0898 500 • PRINTED IN USA
PC FAB DRAWI
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NOTES: UNLESS OTHERWISE SPECIFIED
1. MATERIAL: FR4 OR EQUIVALENT EPOXY, 2 OZ COPPER CLAD
THICKNESS 0.062 ±0.006 TOTAL OF 2 LAYERS
2. FINISH: ALL PLATED HOLES 0.001 MIN/0.0015 MAX COPPER PLATE
ELECTRODEPOSITED TIN-LEAD COMPOSITION BEFORE
REFLOW, SOLDER MASK OVER BARE COPPER (SMOBC)
3. SOLDER MASK: BOTH SIDES USING SR1020 OR EQUIVALENT
4. SILKSCREEN: USING WHITE NONCONDUCTIVE EPOXY INK
5. ALL DIMENSIONS ARE IN INCHES
D D
D
D
D
D
D
C
C
B
AA
AA
A
AAA
A
A
A
A
B
2.00
2.00
NUMBER
SYMBOL DIAMETER OF HOLES
A 0.020 14
B 0.023 14
C 0.072 2
D 0.095 7
