503I18 [Linear]
High Efficiency Inductorless Step-Down DC/DC Converters; 高效率电感降压型DC / DC转换器
| 型号： | 503I18 |
| 厂家： | 
Linear |
| 描述： | High Efficiency Inductorless Step-Down DC/DC Converters |
| 文件： | 总12页 (文件大小：192K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
LTC1503-1.8/LTC1503-2
High Efficiency Inductorless
Step-Down DC/DC Converters
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FEATURES
DESCRIPTIO
The LTC®1503-1.8/LTC1503-2 are switched capacitor
step-down DC/DC converters that produce a regulated
output from a 2.4V to 6V input. The parts use switched
capacitor fractional conversion to achieve high efficiency
over the entire input range. No inductors are required.
Internal circuitry controls the step-down conversion ratio
to optimize efficiency as the input voltage and load condi-
tions vary. Typical efficiency is 25% higher than that of a
low dropout (LDO) linear regulator.
■
Input Voltage Range: 2.4V to 6V
■
Fixed Output Voltages: 1.8V ±4%, 2V ±4%
■
Output Current: Up to 100mA
No Inductors
■
■
Typical Efficiency 25% Higher than LDOs
■
Low Operating Current: 25µA
■
■
■
■
■
■
Low Shutdown Current: 5µA
600kHz Switching Frequency
Shutdown Disconnects Load from VIN
Soft-Start Limits Inrush Current at Turn-On
Short-Circuit and Overtemperature Protected
Available in 8-Pin MSOP and SO Packages
Regulation is achieved by sensing the output voltage and
enabling the internal switching network as needed to
maintain a fixed output voltage. This method of regulation
enables the parts to achieve high efficiency at extremely
lightloads. Lowoperatingcurrent(25µAwithnoload, 5µA
in shutdown) and low external parts count (two 1µF flying
capacitors and two 10µF bypass capacitors) make the
LTC1503-1.8/LTC1503-2 ideally suited for space con-
strained battery-powered applications. The parts are fully
short-circuit and overtemperature protected.
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APPLICATIO S
■
Cellular Phones
■
Handheld Computers
■
Smart Card Readers
Low Power DSP Supplies
Portable Electronic Equipment
Handheld Medical Instruments
■
■
The LTC1503-1.8/LTC1503-2 are available in 8-pin MSOP
and SO packages.
■
, LTC and LT are registered trademarks of Linear Technology Corporation.
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TYPICAL APPLICATIO
Efficiency vs Input Voltage
100
I
= 100mA
OUT
Single Li-Ion to 2V DC/DC Converter
80
60
40
20
LTC1503-2
4
2
3
5
1
8
6
7
V
= 2V
OUT
OUT
I
= 1mA
V
V
OUT
IN
OUT
–
I
= 100mA
1-CELL Li-Ion OR
3-CELL NiMH
10µF
10µF
–
C1
C1
C2
C2
1µF
1µF
+
+
“IDEAL” LDO
SHDN/SS GND
1503-1.8/2 TA01
LTC1503-2
= 2V
V
OUT
4
5
2
6
3
INPUT VOLTAGE (V)
1503-1.8/2 TA02
1
LTC1503-1.8/LTC1503-2
W W
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ABSOLUTE AXI U RATI GS
(Note 1)
VIN, C1+, C1–, C2+, C2– to GND............... –0.3V to 6.5V
SHDN/SS to GND......................... –0.3V to (VIN + 0.3V)
Industrial Temperature Range ............... –40°C to 85°C
Specified Temperature Range (Note 2)... –40°C to 85°C
Storage Temperature Range ................ –65°C to 150°C
Lead Temperature (Soldering, 10 sec)................. 300°C
V
OUT Short-Circuit Duration............................. Indefinite
Commercial Temperature Range ............ –40°C to 85°C
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PACKAGE/ORDER I FOR ATIO
ORDER PART
NUMBER
ORDER PART
TOP VIEW
NUMBER
TOP VIEW
–
V
1
2
3
4
8
7
6
5
C2
OUT
LTC1503CMS8-1.8
LTC1503CMS8-2
LTC1503CS8-1.8
LTC1503CS8-2
LTC1503IS8-1.8
LTC1503IS8-2
–
V
1
2
3
4
8 C2
OUT
–
–
C1
GND
C1
7 GND
+
+
6 C2
C1
+
+
C1
C2
5 SHDN/SS
V
IN
V
IN
SHDN/SS
MS8 PACKAGE
8-LEAD PLASTIC MSOP
MS8 PART MARKING
S8 PACKAGE
8-LEAD PLASTIC SO
TJMAX = 125°C, θJA = 150°C/W
S8 PART MARKING
150318 503I18
TJMAX = 125°C, θJA = 200°C/W
LTFX
LTHN
15032
1503I2
Consult factory for Military grade parts.
ELECTRICAL CHARACTERISTICS
The ● denotes specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C.
VIN = VIN(MIN) to VIN(MAX), C1 = C2 = 1µF, CIN = COUT = 10µF unless otherwise noted.
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
V
V
Operating Voltage
IN
OUT
●
2.4
6
V
LTC1503-1.8, 0mA < I
< 100mA
< 100mA
●
●
1.728
1.920
1.8
2.0
1.872
2.080
V
V
OUT
LTC1503-2, 0mA < I
OUT
V
V
Operating Current
I
= 0mA
OUT
●
●
25
5
50
10
µA
µA
IN
IN
Shutdown Current
SHDN/SS = 0V
LTC1503-X, V = 3.6V, I
Output Ripple Voltage
Efficiency
= 100mA
25
mV
P-P
IN
OUT
OUT
LTC1503-2, V = 3.6V, I
= 100mA
82.9
600
0.35
–2
%
IN
Switching Frequency
SHDN/SS Input Threshold
SHDN/SS Input Current
Oscillator Free Running
kHz
V
●
0.2
0.5
V
V
= 0V (Note 3)
●
●
–3.5
–1
–1
1
µA
µA
SHDN/SS
SHDN/SS
= V
IN
V
V
Short-Circuit Current
Turn-On Time
V
= 0V (Note 4)
OUT
●
8
22
50
mA
OUT
OUT
C
C
= 0nF, V = 3.6V, C
= 10µF
0.1
8
ms
ms
SS
SS
IN
OUT
= 10nF
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 3: Currents flowing into the device are positive polarity. Currents
flowing out of the device are negative polarity.
Note 2: The LTC1503C is guaranteed to meet specified performance from
0°C to 70°C and is designed, characterized and expected to meet these
extended temperature limits, but are not tested at –40°C and 85°C. The
LTC1503I is guaranteed to meet the extended temperature limits.
Note 4: When V
is less than 150mV, I
is limited to much less than
OUT
OUT
the maximum rated output current to prevent damage to the output
devices.
2
LTC1503-1.8/LTC1503-2
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TYPICAL PERFOR A CE CHARACTERISTICS
LTC1503-X Input Operating
Current vs Input Voltage
LTC1503-X Input Shutdown
Current vs Input Voltage
LTC1503-1.8
Output Voltage vs Input Voltage
50
40
30
20
10
1.90
10
7.5
5
V
V
= 0V
SHDN
I
= 0mA
I
= 50mA
OUT
OUT
OUT
/SS = 0V
1.85
1.80
1.75
1.70
T
= –40°C
A
T
= –40°C
A
T
T
A
= –40°C
T
A
= 85°C
T
A
= 25°C
= 85°C
A
T
= 25°C
A
T
A
= 85°C
T
A
= 25°C
2.5
0
4
5
4
5
2
6
4
2
6
3
2
5
6
3
3
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
1503 G01
1503-1.8/2 G03
1503-1.8/2 TA02
LTC1503-1.8
Efficiency vs Input Voltage
LTC1503-2
Output Voltage vs Input Voltage
LTC1503-1.8
Efficiency vs Output Current
2.10
2.05
2.00
1.95
1.90
100
100
80
60
40
20
0
T
= 25°C
T = 25°C
A
A
I
= 50mA
OUT
I
= 100mA
OUT
80
60
40
20
I
= 1mA
OUT
T
= –40°C
A
T
A
= 85°C
“IDEAL”
LDO
T
= 25°C
A
V
V
V
V
V
= 5V
IN
IN
IN
IN
IN
= 4.4V
= 3.6V
= 3V
= 2.4V
4
5
4
5
2
6
2
6
3
3
0.1
10
OUTPUT CURRENT (mA)
0.01
1
100
1000
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
1503 G03
1503-1.8/2 G05
1503-1.8/2 G06
LTC1503-2
Efficiency vs Output Current
LTC1503-1.8
Output Voltage vs Output Current
LTC1503-2
Output Voltage vs Output Current
100
80
60
40
20
0
1.84
1.82
1.80
1.78
1.76
1.74
2.04
2.02
2.00
1.98
1.96
1.94
T
= 25°C
V
= 3.3V
V
= 3.3V
A
IN
IN
T
= –40°C
T
= –40°C
A
A
T
= 85°C
= 25°C
T
= 85°C
= 25°C
A
A
A
A
T
T
V
V
V
V
V
= 5V
IN
IN
IN
IN
IN
= 4.4V
= 3.6V
= 3V
= 2.4V
0.1
0.01
0.1
1
10
100
1000
0.01
0.1
1
10
100
0.01
1
10
OUTPUT CURRENT (mA)
100
1000
1000
OUTPUT CURRENT (mA)
OUTPUT CURRENT (mA)
1503-1.8/2 G07
1503-1.8/2 G08
1503-1.8/2 G09
3
LTC1503-1.8/LTC1503-2
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TYPICAL PERFOR A CE CHARACTERISTICS
LTC1503-X Output Short-Circuit
Current vs Input Voltage
LTC1503-X Start-Up Time
vs Soft-Start Capacitor
40
100
10
V
OUT
SHORTED TO GND
V
IN
= 3.6V
30
20
10
0
T
= –40°C
T
= –40°C
A
T
A
1
T
= 25°C
A
= 85°C
A
T
= 25°C
A
T
= 85°C
A
0.1
0.01
4
5
1
2
6
0.01
10
100
3
0.1
INPUT VOLTAGE (V)
SOFT-START CAPACITOR (nF)
1503-1.8/2 G10
1503-1.8/2 G10
Output Load Transient Response
(LTC1503-1.8,1mA to 100mA Step)
Output Ripple, COUT = 10µF
Output Ripple, COUT = 22µF
100mA
IOUT
50mA/DIV
VOUT
10mV/DIV
AC COUPLED
VOUT
10mV/DIV
AC COUPLED
1mA
VOUT
50mV/DIV
AC COUPLED
1ms/DIV
1503-1.8/2 G12
VIN = 3.6V
OUT = 2V
IOUT = 100mA
COUT = 10µF CERAMIC
5µs/DIV
1503-1.8/2 G13
VIN = 3.6V
OUT = 2V
IOUT = 100mA
COUT = 22µF CERAMIC
5µs/DIV
1503-1.8/2 G14
V
V
U
U
U
PI FU CTIO S
VOUT (Pin 1): Regulated Output Voltage. VOUT is discon-
nected from VIN during shutdown. Bypass VOUT to ground
with a ≥10µF low ESR capacitor.
C1– (Pin 2): Flying Capacitor One Negative Terminal.
C1+ (Pin 3): Flying Capacitor One Positive Terminal.
output. Holding the SHDN/SS pin below 0.25V will force
the part into shutdown mode. An internal pull-up current
of2µAwillforcetheSHDN/SSvoltagetoclimbtoVIN once
the device driving the pin is forced into a Hi-Z state. To
limit inrush current on start-up, connect a capacitor
between the SHDN/SS pin and ground. Capacitance on
theSHDN/SSpinwilllimitthedV/dtofthepinduringturn-
on which, in turn, will limit the dV/dt of VOUT. By selecting
an appropriate soft-start capacitor for a known output
capacitor, the user can control the inrush current during
VIN (Pin 4): Input Voltage. VIN may be between 2.4V and
6V.BypassVIN togroundwitha ≥10µFlowESRcapacitor.
SHDN/SS (Pin 5): Shutdown/Soft-Start Control. The pin
is designed to be driven with an external open-drain
4
LTC1503-1.8/LTC1503-2
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U
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PI FU CTIO S
turn-on (see Applications Information). If neither of the
two functions are desired, the pin may be floated or tied
to VIN.
C2+ (Pin 6): Flying Capacitor Two Positive Terminal.
GND (Pin 7): Ground. Connect to a ground plane for best
performance.
C2– (Pin 8): Flying Capacitor Two Negative Terminal.
W
BLOCK DIAGRA
V
IN
680k
330k
C
IN
+
–
+
C1
–
C1
STEP-DOWN
MODE
CONTROL
CHARGE
+
PUMP
C2
C2
+
–
–
990k
V
OUT
V
OUT
C
OUT
–
+
SHORT CIRCUIT
+
150mV
800k
–
+
MODE SKIP
COMP2
10mV
+
–
+
REG ENABLE
600kHz
OSCILLATOR
COMP1
V
IN
–
+
1.2M
SOFT-START
V
REF
RAMP
2µA
350mV
+
1.2V
REF
SHDN/SS
V
+
–
GND
SHDN
+
350mV
LTC1503-2
1503-1.8/2 BD
5
LTC1503-1.8/LTC1503-2
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APPLICATIO S I FOR ATIO
S4
φ2
S1
φ1
General Operation
+
C1
V
IN
V
OUT
The two most common methods for providing regulated
step-downDC/DCconversionarelinearDC/DCconversion
(used by LDOs) and inductor-based DC/DC conversion.
Linearregulationprovideslowcostandlowcomplexity,but
the conversion efficiency is poor since all of the load cur-
rent must come directly from VIN. Inductor-based step-
down conversion provides the highest efficiency, but the
solution cost and circuit complexity are much higher. The
LTC1503-Xprovidestheefficiencyadvantagesassociated
with inductor-based circuits as well as the cost and sim-
plicity advantages of an inductorless converter.
C1
(EXTERNAL)
S3
φ2
–
C1
1503-1.8/2 F01a
S2
φ1
Figure 1a. Step-Down Charge Pump in 2-to-1 Mode
S1 and S2 across VOUT. If the voltage on C1 is greater than
the voltage on COUT, charge is transferred from C1 onto
COUT. On phase two, the top plate of C1 is connected to VIN
and the bottom plate is connected to VOUT. If the voltage
across C1 is less than VIN/2 during phase two, charge will
be transferred from C1 onto COUT thereby boosting the
voltage on COUT and raising the voltage across C1. Thus,
in 2-to-1 mode, charge transfer from C1 onto COUT occurs
on both phases of the clock, and the voltage on COUT is
driven towards 1/2VIN until the output is back in regula-
tion. Since charge current is sourced from ground on
phase one of the clock, current multiplication is realized
with respect to VIN, i.e., IVOUT equals approximately 2 •
IVIN. This results in significant efficiency improvement
relative to a linear regulator.
The LTC1503-X is a switched capacitor step-down DC/DC
converter. The part uses an internal switch network and
fractionalconversionratiostoachievehighefficiencyover
widely varying VIN and output load conditions. Internal
control circuitry selects the appropriate step-down con-
version ratio based on VIN, VOUT and load conditions to
optimizeefficiency. Theparthasthreepossiblestep-down
modes: 2-to-1, 3-to-2 or 1-to-1 (gated switch) step-down
mode. Only two external flying caps are needed to operate
in all three modes. 2-to-1 mode is chosen when VIN is
greater than two times the desired VOUT. 3-to-2 mode is
chosen when VIN is greater than 1.5 times VOUT but less
than 2 times VOUT. 1-to-1 mode is chosen when VIN falls
below 1.5 times VOUT. An internal mode skip function will
switch the step-down ratio as needed to maintain output
regulation under heavy load conditions.
The 3-to-2 conversion mode also uses a nonoverlapping
clock for switch control but requires two flying capacitors
and a total of seven switches (see Figure 1b). On phase
one, C1 and C2 are connected in series across VOUT. If the
sumofthevoltagesacrossC1andC2isgreaterthanVOUT
,
Regulationisachievedbysensingthedivideddownoutput
voltage and enabling the charge pump as needed to boost
the output back into regulation. This method of regulation
allows the LTC1503-X to achieve high efficiency at very
light loads. The part has shutdown capability as well as
user controlled inrush current limiting. In addition, the
part can withstand an indefinite short-circuit condition on
VOUT and is also overtemperature protected.
charge is transferred from the flying caps onto COUT
thereby reducing the average voltage on the flying caps
and raising the voltage on the output capacitor. On phase
two, the two flying capacitors are connected on parallel
between VIN and VOUT. Since the average voltage across
thetwocapacitorsduringphaseoneisVOUT/2, chargewill
be transferred from VIN to VOUT through the two flying
caps if VIN minus VOUT/2 is greater than VOUT. In this
manner, charge is again transferred from the flying caps
to the output on both phases of the clock, and the voltage
on COUT is driven towards (2/3)VIN until the part is back in
regulation. As in 2-to-1 mode, charge current is sourced
from ground on phase one of the clock which results in
increased power efficiency. IVOUT in 3-to-2 mode equals
Step-Down Charge Pump Operation
Figure 1a shows the charge pump switch configuration
that is used for 2-to-1 step down. When the charge pump
is enabled in this mode, a two phase nonoverlapping clock
generates the switch control signals. On phase one of the
clock, flying capacitor C1 is connected through switches
approximately (3/2)IVIN
.
6
LTC1503-1.8/LTC1503-2
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APPLICATIO S I FOR ATIO
S5
S1
maintainregulation. ThiswillonlyoccurasVIN/VOUT nears
a3-to-2or1-to-1transitionpoint.Forexample,underlight
load conditions, the LTC1503-X can operate in 2-to-1
mode when VIN equals 4.1V with greater than 90% effi-
ciency. However, when the load is increased, the part can
no longer supply enough output current in 2-to-1 mode to
maintain regulation. This causes VOUT to droop below the
regulation point until COMP2 trips and forces the part to
skip from 2-to-1 mode to 3-to-2 mode. The COMP2
threshold is about 17mV (VOUT referred) below the main
comparator regulation point. Hysteresis in COMP2 will
force the part to transition in and out of mode skipping.
This will result in a slight VOUT decrease of approximately
20mV under mode skipping conditions.
+
C1
φ2
φ1
V
IN
V
OUT
C1
(EXTERNAL)
S4
–
C1
φ2
S2
φ1
S7
φ2
+
C2
C2
(EXTERNAL)
S6
φ2
–
C2
S3
φ1
GND
Shutdown/Soft-Start Operation
1503-1.8/2 F01b
The SHDN/SS pin is used to implement both low current
shutdown and soft-start. The soft-start feature limits
inrush currents when the regulator is initially powered up
or taken out of shutdown. Forcing a voltage lower than
0.35V (typ) will put the part into shutdown mode. Shut-
down mode disables all control circuitry and forces the
chargepumpVOUT intoahighimpedancestate.A2µApull-
up current on the SHDN/SS pin will force the part into
active mode if the pin is left floating or is driven with an
open-drain output that is in a high impedance state. If the
pin is not driven with an open-drain device, it must be
forced to a logic high voltage of 2.2V (min) to ensure
proper VOUT regulation. The SHDN/SS pin should not be
driven to a voltage higher than VIN.
Figure 1b. Step-Down Charge Pump in 3-to-2 Mode
In 1-to-1 mode, switch S1 and S2 are connected in series
between VIN and VOUT as needed to boost VOUT back into
regulation (see Figure 1c). The REG ENABLE signal from
the main comparator (COMP1) controls switches S1 and
S2 directly. Since all of the VOUT current is sourced from
VIN, the efficiency in 1-to-1 mode is approximately equal
to that of a linear regulator.
+
C1
S2
S1
V
IN
V
OUT
C1
(EXTERNAL)
–
C1
1503-1.8/2 F01c
Toimplementsoft-start,theSHDN/SSpinmustbedriven
with an open-drain device and a capacitor must be
connectedfromtheSHDN/SSpintoGND.Oncetheopen-
drain device is turned off, a 2µA pull-up current will begin
charging the external SS capacitor and force the voltage
on the pin to ramp towards VIN. As soon as the SHDN
threshold is reached (0.35V typ), the internal reference
voltage which controls the VOUT regulation point will
follow the ramp voltage on the SHDN/SS pin (minus a
0.35V offset to account for the SHDN threshold) until the
reference reaches its final band gap voltage. This occurs
when the voltage on the SHDN/SS pin reaches
Figure 1c. Step-Down Charge Pump in 1-to-1 Mode
Mode Selection and Mode Skipping
The optimal step-down conversion mode is chosen based
on VIN to VOUT differential voltage and output load condi-
tions. Two internal comparators are used to select the
default step-down mode based on the VIN and VOUT
voltage. A separate comparator (COMP2) is used to sense
a droop on VOUT due to a heavy output load and force the
charge pump to skip to a higher output current mode to
7
LTC1503-1.8/LTC1503-2
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APPLICATIO S I FOR ATIO
approximately1.9V. SincetheramprateontheSHDN/SS
pin controls the ramp rate on VOUT, the average inrush
current can be controlled through selection of CSS and
COUT.Forexample,a4.7nFcapacitoronSHDN/SSresults
in a 4ms ramp time from 0.35V to 1.9V on the pin. If COUT
is 10µF, the 4ms VREF ramp time results in an average
COUT charge current of only 5mA (see Figure 2c).
Capacitor Selection
For best performance, it is recommended that low ESR
capacitors be used for CIN and COUT to reduce noise and
ripple. If the ESR of the output capacitor is too high
(>0.5Ω), both efficiency and output load regulation may
bedegraded. TheCIN andCOUT capacitorsshouldbeeither
ceramic or tantalum and should be 10µF or greater. If the
input source impedance is very low (<0.5Ω), CIN may not
be needed. Ceramic capacitors are recommended for the
flying caps C1 and C2 with values of 0.47µF to 2.2µF.
Smaller values may be used in low output current applica-
tions (e.g., IOUT < 10mA). For best performance choose
the same capacitance value for both C1 and C2.
1
V
OUT
R
LOAD
LTC1503-X
SHDN/SS
5
1503-1.8/2 F02a
ON OFF V
C
SS
CTRL
Output Ripple
(a)
Normal LTC1503-X operation produces voltage ripple on
theVOUT pin. Outputvoltagerippleisrequiredfortheparts
to regulate. Low frequency ripple exists due to the hyster-
esisinthesensecomparatorandpropagationdelaysinthe
chargepumpenable/disablecircuits.Highfrequencyripple
is also present mainly from the ESR (equivalent series
resistance) in the output capacitor. Typical output ripple
(VIN = 3.6V) under maximum load is 25mV peak-to-peak
with a low ESR 10µF output capacitor.
VCTRL
2V/DIV
VOUT
1V/DIV
The magnitude of ripple voltage depends on several fac-
tors. High input voltages increase the output ripple since
morechargeisdeliveredtoCOUT perchargingcycle. Large
outputcurrentloadand/orasmalloutputcapacitor(<10µF)
results in higher ripple due to higher output voltage dV/dt.
HighESRcapacitors(ESR>0.5Ω)ontheoutputpincause
high frequency voltage spikes on VOUT with every clock
cycle.
LTC1503-2
CSS = 0nF
2ms/DIV
1503-1.8/2 F02b
COUT = 10µF
RLOAD = 50Ω
(b)
VCTRL
2V/DIV
There are several ways to reduce the output voltage ripple
(see Figure 3). A larger COUT capacitor (22µF or greater)
will reduce both the low and high frequency ripple due to
the lower COUT charging and discharging dV/dt and the
lower ESR typically found with higher value (larger case
size) capacitors. A low ESR ceramic output capacitor will
minimize the high frequency ripple, but will not reduce the
low frequency ripple unless a high capacitance value is
chosen.Areasonablecompromiseistousea10µFto22µF
tantalum capacitor in parallel with a 1µF to 3.3µF ceramic
VOUT
1V/DIV
LTC1503-2
CSS = 4.7nF
2ms/DIV
1503-1.8/2 F02b
C
OUT = 10µF
RLOAD = 50Ω
(c)
Figure 2. Shutdown/Soft-Start Operation
8
LTC1503-1.8/LTC1503-2
W U U
APPLICATIO S I FOR ATIO
capacitor on VOUT to reduce both the low and high fre-
quencyripple. AnRCfiltermayalsobeusedtoreducehigh
frequency voltage spikes.
U
is disabled once VOUT reaches 0.7V (typ). The part can
survive an indefinite short from VOUT to GND.
Layout Considerations
LTC1503-X
For best regulation and noise performance, careful board
layout is required. Improper bypassing and grounding
may lead to poor load regulation and output ripple perfor-
mance. All capacitors, especially CIN and COUT, must be as
close as possible to the VIN and VOUT pins. Connecting the
GND pin and all bypass capacitors to an uninterrupted
ground plane is also advised. See Figure 4 for recom-
mended component placement and grounding.
V
V
V
OUT
OUT
OUT
+
+
10µF
1µF
TANTALUM
CERAMIC
LTC1503-X
0.5Ω
V
OUT
+
10µF
TANTALUM
10µF
TANTALUM
1503-1.8/2 F03
Figure 3. Output Ripple Reduction Techniques
C
OUT
Protection Features
V
OUT
LTC1503-X
GND
The LTC1503-X contains both thermal shutdown and
short-circuit protection features. The charge pump will
shut down when the junction temperature reaches ap-
proximately 150°C and will resume operation once the
junctiontemperaturehasdroppedbackto125°C. Thepart
willlimitoutputcurrentto20mA(typ)whenashort-circuit
condition (VOUT < 150mV) exists to prevent damage to the
internal switches. During start-up, the 20mA current limit
C2
C1
V
SHDN/SS
IN
C
1503-1.8/2 F04
IN
Figure 4. Recommended Component Placement and Grounding
9
LTC1503-1.8/LTC1503-2
U
PACKAGE DESCRIPTIO
Dimensions in inches (millimeters) unless otherwise noted.
MS8 Package
8-Lead Plastic MSOP
(LTC DWG # 05-08-1660)
0.118 ± 0.004*
(3.00 ± 0.102)
8
7
6
5
0.118 ± 0.004**
(3.00 ± 0.102)
0.193 ± 0.006
(4.90 ± 0.15)
1
0.040 ± 0.006
2
3
4
0.034 ± 0.004
(0.86 ± 0.102)
(1.02 ± 0.15)
0.007
(0.18)
0° – 6° TYP
SEATING
PLANE
0.012
(0.30)
REF
0.021 ± 0.006
(0.53 ± 0.015)
0.006 ± 0.004
(0.15 ± 0.102)
0.0256
(0.65)
BSC
MSOP (MS8) 1098
* DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS. MOLD FLASH,
PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE
** DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS.
INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE
10
LTC1503-1.8/LTC1503-2
U
PACKAGE DESCRIPTIO
Dimensions in inches (millimeters) unless otherwise noted.
S8 Package
8-Lead Plastic Small Outline (Narrow 0.150)
(LTC DWG # 05-08-1610)
0.189 – 0.197*
(4.801 – 5.004)
7
5
8
6
0.150 – 0.157**
(3.810 – 3.988)
0.228 – 0.244
(5.791 – 6.197)
1
3
4
2
0.010 – 0.020
(0.254 – 0.508)
× 45°
0.053 – 0.069
(1.346 – 1.752)
0.004 – 0.010
(0.101 – 0.254)
0.008 – 0.010
(0.203 – 0.254)
0°– 8° TYP
0.016 – 0.050
(0.406 – 1.270)
0.050
(1.270)
BSC
0.014 – 0.019
(0.355 – 0.483)
TYP
*DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH
SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE
**DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD
FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE
SO8 1298
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-
tationthattheinterconnectionofitscircuitsasdescribedhereinwillnotinfringeonexistingpatentrights.
11
LTC1503-1.8/LTC1503-2
U
TYPICAL APPLICATIO
DC/DC Converter with Shutdown and Soft-Start
LTC1503-1.8
4
2
3
5
1
8
6
7
V
= 1.8V
= 100mA
OUT
OUT
V
V
OUT
IN
I
1-CELL Li-Ion OR
3-CELL NiMH
10µF
1µF
10µF
–
–
C1
C1
C2
1µF
+
+
C2
SHDN/SS GND
ON OFF
2N7002
10nF
1503-1.8/2 TA03
RELATED PARTS
PART NUMBER
LTC1474/LTC1475
LTC1502-3.3
DESCRIPTION
COMMENTS
Low Quiescent Current Step-Down DC/DC Converter
Single Cell to 3.3V Quadrupler Charge Pump
I
to 250mA, I = 10µA; 8-Lead MSOP
OUT Q
V
= 0.9V to 1.8V, I
= 10mA; I = 40µA
OUT Q
IN
LTC1514/LTC1515
Micropower, Regulated 5V Step-Up/Step-Down
Charge Pump DC/DC Converters
2V to 10V Input Range; Up to 50mA Output Current: Short-Circuit
and Overtemperature Protected
LTC1555/LTC1556
LTC1627
SIM Power Supply and Level Translator
Monolithic Synchronous Buck Step-Down
Switching Regulator
Step-Up/Step-Down Charge Pump Generates 5V or 3V
2.65V to 8.5V Input Range; V
from 0.8V, I
to 500mA;
OUT
OUT
Low Dropout Operation; 100% Duty Cycle
LTC1754-3.3
LTC1754-5
3.3V Charge Pump with Shutdown in SOT-23
5V Charge Pump with Shutdown in SOT-23
50mA Output Current, I = 13µA
CC
50mA Output Current, I = 13µA
CC
150312f LT/TP 0200 4K • PRINTED IN USA
LinearTechnology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
12
●
●
LINEAR TECHNOLOGY CORPORATION 1999
(408)432-1900 FAX:(408)434-0507 www.linear-tech.com
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