1
LTC1174
LTC1174-3.3/LTC1174-5
1174fe
High Efficiency
Step-Down and Inverting
DC/DC Converter
High Efficiency Step-Down Converter LTC1174-5 Efficiency
■
High Efficiency: Up to 94%
■
Peak Inductor Current Independent of
Inductor Value
■
Short-Circuit Protection
■
Optimized for 5V to – 5V Applications
■
Wide V
IN
Range: 4V to 18.5V
■
Low Dropout Operation
■
Low-Battery Detector
■
Pin Selectable Current Limit
■
Internal 0.9Ω Power Switch: V
IN
= 9V
■
Only Four External Components Required
■
130µA Standby Current
■
Active Low Micropower Shutdown
■
Distributed Power Systems
■
Step-Down Converters
■
Inverting Converters
■
Memory Backup Supply
■
Portable Instruments
■
Battery-Powered Equipment
The LTC
®
1174 is a simple current mode DC/DC converter
ideally suited for 9V to 5V, 5V to 3.3V or 5V to –5V
operation. With an internal 0.9Ω switch (at a supply
voltage of 9V), the LTC1174 requires only four external
components to construct a complete high efficiency
DC/DC converter.
Under a no load condition the LTC1174 draws only 130µA.
In shutdown, it draws a mere 1µA making this converter
ideal for current sensitive applications. In dropout, the
internal P-channel MOSFET switch is turned on continu-
ously allowing the user to maximize the life of the battery
source.
The maximum inductor current of the LTC1174 family is
pin selectable to either 340mA or 600mA, optimizing
efficiency for a wide range of applications. Operation up to
200kHz permits the use of small surface mount inductors
and capacitors.
For applications requiring higher output current or ultra-
high efficiency, see the LTC1148 data sheet.
FEATURES
DESCRIPTIO
U
APPLICATIO S
U
TYPICAL APPLICATIO
U
V
IN
9V
3
LTC1174-5
LB
IN
LB
OUT
I
PGM
GND
V
IN
SHUTDOWN
V
OUT
SW
2
7
6
8
1
5
4
100µH
†
100µF**
10V
5V
175mA
15µF*
25V
×3
1N5818
1174 TA01
*
**
†
(3) AVX TPSD156K025
AVX TPSD107K010
COILTRONICS CTX100-4
+
+
LOAD CURRENT (mA)
1
EFFICIENCY (%)
100
95
90
85
80
75
70 10 100
1174 TA02
200
V
IN
= 6V
V
IN
= 9V
L = 100µH
V
OUT
= 5V
I
PGM
= 0V
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
2
LTC1174
LTC1174-3.3/LTC1174-5
1174fe
(Note 1)
(Voltage Referred to GND Pin)
Input Supply Voltage (Pin 6)
LTC1174 ........................................... –0.3V to 13.5V
LTC1174HV ...................................... –0.3V to 18.5V
Switch Current (Pin 5) .............................................. 1A
Switch Voltage (Pin 5)
LTC1174 ................................................. V
IN
– 13.5V
LTC1174HV ............................................ V
IN
– 18.5V
Operating Temperature Range
LTC1174CX ............................................ 0°C to 70°C
LTC1174IX ........................................ – 40°C to 85°C
Junction Temperature (Note 2)............................ 125°C
Storage Temperature Range ................ –65°C to 150°C
Lead Temperature (Soldering, 10 sec)................. 300°C
ORDER PART NUMBER S8 PART MARKING
LTC1174CS8
LTC1174CS8-3.3
LTC1174CS8-5
LTC1174IS8
LTC1174HVCS8
LTC1174HVCS8-3.3
LTC1174HVCS8-5
LTC1174HVIS8
1174
117433
117450
1174I
1174H
1174H3
1174H5
1174HI
T
JMAX
= 125°C, θ
JA
= 150°C/W
ORDER PART NUMBER
LTC1174CN8
LTC1174CN8-3.3
LTC1174CN8-5
LTC1174IN8
LTC1174HVCN8
LTC1174HVCN8-3.3
LTC1174HVCN8-5
T
JMAX
= 125°C, θ
JA
= 110°C/W
ABSOLUTE AXI U RATI GS
WWWU
PACKAGE/ORDER I FOR ATIO
UU
W
1
2
3
4
8
7
6
5
TOP VIEW
V
OUT
(V
FB
*)
LB
OUT
LB
IN
GND
SHUTDOWN
I
PGM
V
IN
SW
N8 PACKAGE
8-LEAD PDIP
* ADJUSTABLE OUTPUT VERSION
1
2
3
4
8
7
6
5
TOP VIEW
S8 PACKAGE
8-LEAD PLASTIC SO
* ADJUSTABLE OUTPUT VERSION
V
OUT
(V
FB
*)
LB
OUT
LB
IN
GND
SHUTDOWN
I
PGM
V
IN
SW
Order Options Tape and Reel: Add #TR
Lead Free: Add #PBF Lead Free Tape and Reel: Add #TRPBF
Lead Free Part Marking: http://www.linear.com/leadfree/
Consult LTC Marketing for parts specified with wider operating temperature ranges.
The ● denotes specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VIN = 9V, VSHUTDOWN = VIN, IPGM = 0V, unless otherwise noted.
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
I
FB
Feedback Current LTC1174/LTC1174HV 1 µA
V
FB
Feedback Voltage LTC1174/LTC1174HV ●1.20 1.25 1.30 V
V
OUT
Regulated Output Voltage LTC1174-3.3/LTC1174HV-3.3 ●3.14 3.30 3.46 V
LTC1174-5/LTC1174V-5 ●4.75 5.00 5.25 V
∆V
OUT
Output Voltage Line Regulation V
IN
= 6V to 12V, I
LOAD
= 100mA, I
PGM
= V
IN
(Note 3) 10 70 mV
ELECTRICAL CHARACTERISTICS
3
LTC1174
LTC1174-3.3/LTC1174-5
1174fe
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
Output Voltage Load Regulation LTC1174-3.3 (Note 3)
20mA < I
LOAD
< 175mA, I
PGM
= 0V –5 –70 mV
20mA < I
LOAD
< 400mA, I
PGM
= V
IN
–45 –70 mV
LTC1174-5 (Note 3)
20mA < I
LOAD
< 175mA, I
PGM
= 0V –5 –70 mV
20mA < I
LOAD
< 400mA, I
PGM
= V
IN
–50 –70 mV
I
Q
Input DC Supply Current (Note 4) Active Mode
LTC1174: 4V < V
IN
< 12V, I
PGM
= 0V 450 600 µA
LTC1174HV: 4V < V
IN
< 16V, I
PGM
= 0V 450 600 µA
Sleep Mode
LTC1174: 4V < V
IN
< 12V 130 180 µA
LTC1174HV: 4V < V
IN
< 16V 130 180 µA
SHUTDOWN (Note 4)
LTC1174: V
SHUTDOWN
= 0V, 4V < V
IN
< 12V 1 10 µA
LTC1174HV: V
SHUTDOWN
= 0V, 4V < V
IN
< 16V 2 25 µA
V
LBTRIP
Low-Battery Trip Point 1.25 1.4 V
I
LBIN
Current into Pin 3 0.5 µA
I
LBOUT
Current Sunk by Pin 2 LTC1174: V
LBOUT
= 0.4V 1.0 1.2 1.5 mA
LTC1174HV: V
LBOUT
= 0.4V 0.6 0.8 1.5 mA
V
HYST
Comparator Hysteresis LTC1174/LTC1174HV 7.5 15 30 mV
I
PEAK
Current Limit I
PGM
= V
IN
, V
OUT
= 0V ●0.54 0.60 0.83 A
I
PGM
= 0V, V
OUT
= 0V ●0.27 0.34 0.53 A
R
ON
ON Resistance of Switch LTC1174 ●0.75 1.30 Ω
LTC1174HV ●0.90 1.55 Ω
t
OFF
Switch Off-Time (Note 6) V
OUT
at Regulated Value 3 4 5 µs
V
IH
SHUTDOWN Pin High Minimum Voltage at Pin 8 for Device to Be Active 1.2 V
V
IL
SHUTDOWN Pin Low Maximum Voltage at Pin 8 for Device to Be in Shutdown 0.75 V
I
IH
SHUTDOWN Pin Input Current LTC1174: V
SHUTDOWN
= 12V 0.5 µA
LTC1174HV: V
SHUTDOWN
= 16V 2.0 µA
I
IL
SHUTDOWN Pin Input Current 0 ≤ V
SHUTDOWN
≤ 0.8V 0.5 µA
The ● denotes specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VIN = 9V, VSHUTDOWN = VIN, IPGM = 0V, unless otherwise noted.
ELECTRICAL CHARACTERISTICS
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
V
FB
Feedback Voltage LTC1174I/LTC1174HVI ●1.18 1.25 1.31 V
I
LBOUT
Current Sunk by Pin 2 V
LBOUT
= 0.4V (LTC1174I) ●0.75 1.2 2.0 mA
V
LBOUT
= 0.4V (LTC1174HVI) ●0.50 0.8 1.6 mA
I
PEAK
Current Limit I
PGM
= V
IN
, V
OUT
= 0V (LTC1174I) ●0.54 0.60 0.84 A
I
PGM
= 0V, V
OUT
= 0V (LTC1174I) 0.34 A
I
PGM
= V
IN
, V
OUT
= 0V (LTC1174HVI) ●0.5 0.60 0.86 A
I
PGM
= 0V, V
OUT
= 0V (LTC1174HVI) 0.34 A
t
OFF
Switch Off-Time (Note 6) V
OUT
at Regulated Value (LTC1174I) ●2.0 4 6.0 µs
V
OUT
at Regulated Value (LTC1174HVI) ●1.8 4 6.2 µs
R
ON
Switch On Resistance LTC1174I/LTC1174HVI ●0.9 1.7 Ω
Note 1: Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
The ● denotes specifications which apply over the full operating temperature range,
otherwise specifications are at – 40°C ≤ TA ≤ 85°C. LTC1174I and LTC1174HVI Only.
Note 2: T
J
is calculated from the ambient temperature T
A
and power
dissipation P
D
according to the following formulas:
LTC1174CN8, LTC1174CN8-3.3, LTC1174CN8-5:
T
J
= T
A
+ (P
D
× 110°C/W)
LTC1174CS8, LTC1174CS8-3.3, LTC1174CS8-5:
T
J
= T
A
+ (P
D
× 150°C/W)
4
LTC1174
LTC1174-3.3/LTC1174-5
1174fe
Efficiency vs Load Current Efficiency vs Load Current Efficiency vs Load Current
Efficiency vs Load CurrentEfficiency vs Load Current Efficiency vs Load Current
TYPICAL PERFOR A CE CHARACTERISTICS
UW
LOAD CURRENT (mA)
1
EFFICIENCY (%)
100
95
90
85
80
75
70 10 100
1174 G01
200
V
IN
= 6V
V
IN
= 9V
L = 50µH
V
OUT
= 5V
I
PGM
= 0V
COIL = CTX50-4
LOAD CURRENT (mA)
1
EFFICIENCY (%)
10 100
1174 G02
400
100
95
90
85
80
75
70
L = 50µH
V
OUT
= 5V
I
PGM
= V
IN
COIL = CTX50-4
V
IN
= 6V
V
IN
= 9V
LOAD CURRENT (mA)
1
EFFICIENCY (%)
10 100
1174 G03
500
100
95
90
85
80
75
70
L = 100µH
V
OUT
= 5V
I
PGM
= V
IN
COIL = CTX100-4
V
IN
= 6V
V
IN
= 9V
LOAD CURRENT (mA)
1
EFFICIENCY (%)
10 100
1174 G04
300
100
90
80
70
60
50
L = 50µH
V
OUT
= 3.3V
I
PGM
= 0V
COIL = CTX50-4
V
IN
= 5V
V
IN
= 9V
LOAD CURRENT (mA)
1
EFFICIENCY (%)
10 100
1174 G06
500
100
90
80
70
60
50
L = 100µH
V
OUT
= 3.3V
I
PGM
= V
IN
COIL = CTX100-4
V
IN
= 5V
V
IN
= 9V
LOAD CURRENT (mA)
1
EFFICIENCY (%)
10 100
1174 G05
500
100
90
80
70
60
50
L = 50µH
V
OUT
= 3.3V
I
PGM
= V
IN
COIL = CTX50-4
V
IN
= 5V
V
IN
= 9V
Note 3: Guaranteed by design.
Note 4: Dynamic supply current is higher due to the gate charge being
delivered at the switching frequency.
ELECTRICAL CHARACTERISTICS
Note 5: Current into Pin 6 only, measured without electrolytic input
capacitor.
Note 6: The off-time is wafer-sort trimmed.
5
LTC1174
LTC1174-3.3/LTC1174-5
1174fe
Supply Current in Shutdown
Switch Resistance vs
Input Voltage
Efficiency vs Input Voltage DC Supply Current
Operating Frequency
vs VIN – VOUT Off-Time vs Output Voltage
TYPICAL PERFOR A CE CHARACTERISTICS
UW
INPUT VOLTAGE (V)
5
EFFICIENCY (%)
7910 14
1174 G10
68 11 12 13
95
94
93
92
91
90
89
V
OUT
= 5V
L = 100µH
COIL = CTX100-4
I
LOAD
= 300mA
I
PGM
= V
IN
I
LOAD
= 100mA
I
PGM
= 0V
INPUT VOLTAGE (V)
0
SUPPLY CURRENT (µA)
8
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
1174 G11
414
2610 12
SHUTDOWN = 0V
TA = 25°C
CURRENT INTO PIN 6 ONLY
INPUT VOLTAGE (V)
0
SUPPLY CURRENT (µA)
500
450
400
350
300
250
200
150
100
50
04810
1174 G12
2612 14
ACTIVE MODE
IPGM = VIN
SLEEP MODE
IPGM = 0V
TA = 25°C
(V
IN
– V
OUT
) VOLTAGE (V)
0
NORMALIZED FREQUENCY
9
1174 G13
257
2.0
1.5
1.0
0.5
0
13468
V
OUT
= 5V
T
A
= 25°C
T
A
= 70°C
INPUT VOLTAGE (V)
4
RDS
(ON)
(Ω)
12
1174 G14
6810 14 16 18 20
T
A
= 25°C
1.7
1.6
1.5
1.4
1.3
1.2
1.1
1.0
0.9
0.8
0.7
LTC1174HV
LTC1174
OUTPUT VOLTAGE (V)
0
OFF-TIME (µs)
50
40
30
20
10
04
1174 G15
1235
LTC1174-5
LTC1174HV-5
LTC1174-3.3
LTC1174HV-3.3
Line Regulation
Switch Leakage Current
vs Temperature Efficiency vs Input Voltage
INPUT VOLTAGE (V)
0
∆VOUT (mV)
6
4
2
0
–2
–4
–6
–8
–10
–12
–14 4810
1174 G07
2612 14
ILOAD = 100mA
IPGM = 0V
TEMPERATURE (°C)
0
LEAKAGE CURRENT (nA)
180
160
140
120
100
80
60
40
20
0
40 80 100
1174 G08
20 60
V
IN
= 13.5V
INPUT VOLTAGE (V)
5
EFFICIENCY (%)
14
1174 G09
7912
95
94
93
92
91
90
89
88
87
68
10 11 13
L = 100µH
L = 50µH
V
OUT
= 5V
I
PGM
= 0V
I
LOAD
= 75mA
CORE = CTX (Kool Mµ®)
6
LTC1174
LTC1174-3.3/LTC1174-5
1174fe
(Pin 1 connection shown for LTC1174-3.3 and LTC1174-5, changes create LTC1174)
FU CTIO AL DIAGRA
UU
W
–
+
VTH2
–
+
–
+
VLIM2
VLIM1
IPGM RSENSE
0.1Ω
RESET
VTH1
LBOUT 2
1174 BD
gmVFB
1.25V
REFERENCE
Q
GND 4
5
SW
1
VOUT (VFB)
7
–
+
A1
×
R1*
31.5k
SET
6
VIN
LBIN
3
SHUTDOWN
8
CT
SLEEP
–
+
A3
A4
A5
VFB
* R1 = 51k FOR LTC1174-3.3
R1 = 93.5k FOR LTC1174-5
A2
SW (Pin 5): Drain of the P-Channel MOSFET Switch. Cathode
of Schottky diode must be closely connected to this pin.
V
IN
(Pin 6): Input Supply Voltage. It must be decoupled
close to ground Pin 4.
I
PGM
(Pin 7): Selects the Current Limit of the P-Channel
Switch. With I
PGM
= V
IN
, the current trip point is 600mA and
with I
PGM
= 0V, the current trip value is reduced to 340mA.
SHUTDOWN (Pin 8): Pulling this pin to ground keeps the
internal switch off and puts the LTC1174 in micropower
shutdown.
V
OUT
(V
FB
) (Pin 1): For the LTC1174, this pin connects to the
main voltage comparator’s input. On the LTC1174-3.3 and
LTC1174-5 this pin goes to an internal resistive divider
which sets the output voltage.
LB
OUT
(Pin 2): Open Drain of an N-Channel Pull-Down. This
pin will sink current when Pin 3 (LB
IN
) goes below 1.25V.
During shutdown the state of this pin is indeterminate.
LB
IN
(Pin 3): The “–” Input of the Low-Battery Voltage
Comparator. The “+” input is connected to a reference
voltage of 1.25V.
GND (Pin 4): Ground Pin.
UU
U
PI FU CTIO S
7
LTC1174
LTC1174-3.3/LTC1174-5
1174fe
(Refer to Functional Diagram)
The LTC1174 uses a constant off-time architecture to
switch its internal P-channel power MOSFET. The off-time
is set by an internal timing capacitor and the operating
frequency is a function of V
IN
.
The output voltage is set by an internal resistive divider
(LTC1174-3.3 and LTC1174-5) or an external divider re-
turned to V
FB
Pin 1 (LTC1174). A voltage comparator A1
compares the divided output voltage to a reference voltage
of 1.25V.
To optimize efficiency, the LTC1174 automatically switches
between continuous and Burst Mode
®
operation. The volt-
age comparator is the primary control element when the
device is in Burst Mode operation, while the current com-
parator controls the output voltage in continuous mode.
During the switch“ON” time, switch current flows through
the 0.1Ω sense resistor. When this current reaches the
threshold of the current comparator A2, its output signal will
change state, setting the flip-flop and turning the switch off.
The timing capacitor, C
T
, begins to discharge until its
voltage goes below V
TH1
. Comparator A4 will then trip,
which resets the flip-flop and causes the switch to turn on
again. Also, the timing capacitor is recharged. The inductor
current will again ramp up until the current comparator A2
trips. The cycle then repeats.
When the load is relatively light, the LTC1174 automatically
goes into Burst Mode
operation. The current mode loop is
interrupted when the output voltage reaches the desired
regulated value. The hysteretic voltage comparator A1 trips
when V
OUT
is above the desired output voltage, shutting off
the switch and causing the timing capacitor to discharge.
This capacitor discharges past V
TH1
until its voltage drops
below V
TH2
. Comparator A5 then trips and a sleep signal is
generated.
In sleep mode, the LTC1174 is in standby and the load
current is supplied by the output capacitor. All unused
circuitry is shut off, reducing quiescent current from
0.45mA to 0.13mA. When the output capacitor discharges
by the amount of the hysteresis of the comparator A1, the
P-channel switch turns on again and the process repeats
itself.
Operating Frequency and Inductor
Since the LTC1174 utilizes a constant off-time architecture,
its operating frequency is dependent on the value of V
IN
. The
frequency of operation can be expressed as:
ft
VV
VV Hz
OFF
IN OUT
IN D
=−
+
⎛
⎝
⎜⎞
⎠
⎟
()
1
where t
OFF
= 4µs and V
D
is the voltage drop across the diode.
Note that the operating frequency is a function of the input
and ouput voltage.
Although the size of the inductor does not affect the fre-
quency, it does affect the ripple current. The peak-to-peak
ripple current is given by:
IVV
LA
RIPPLE OUT D PP
=+
⎛
⎝
⎜⎞
⎠
⎟
()
−−
410
6
•
By choosing a smaller inductor, a low ESR output filter
capacitor has to be used (see C
IN
and C
OUT
). Moreover, core
loss will also increase (see Inductor Core Selection section)
due to higher ripple current.
OPERATIO
U
Burst Mode is a registered trademark of Linear Technology Corporation.
8
LTC1174
LTC1174-3.3/LTC1174-5
1174fe
Inductor Core Selection
With the value of L selected, the type of inductor must be
chosen. Basically there are two kinds of losses in an
inductor, core and copper
Core losses are dependent on the peak-to-peak ripple
current and the core material. However it is independent of
the physical size of the core. By increasing the inductance
the inductor’s peak-to-peak ripple current will decrease,
therefore reducing core loss. Utilizing low core loss mate-
rial, such as molypermalloy or Kool Mµ will allow users to
concentrate on reducing copper loss and preventing satu-
ration. Figure 1 shows the effect of different core material on
the efficiency of the LTC1174. The CTX core is Kool Mµ and
the CTXP core is powdered iron (material 52).
Although higher inductance reduces core loss, it increases
copper loss as it requires more windings. When space is not
Figure 1. Efficiency Using Different Types of
Inductor Core Material
APPLICATIO S I FOR ATIO
WUUU
LOAD CURRENT (mA)
1
EFFICIENCY (%)
10 100 500
100
90
80
70
60
50
VIN = 5V
VOUT = 3.3V
IPGM = VIN
CTX50-4
CTX50-4P
1174 F01
LOAD CURRENT (mA)
1
EFFICIENCY (%)
10 100 500
100
90
80
70
60
50
VIN = 5V
VOUT = 3.3V
IPGM = VIN
CTX100-4
CTX100-4P
a premium larger gauge wire can be used to reduce the wire
resistance. This also prevents excessive heat dissipation.
C
IN
In continuous mode the source current of the P-channel
MOSFET is a square wave of duty cycle V
OUT
/V
IN
. To prevent
large voltage transients, a low ESR input capacitor sized for
the maximum RMS current must be used. The C
IN
RMS
current is given by:
IIVVV
VA
RMS
OUT OUT IN OUT
IN RMS
≈−
()
[]
()
12/
This formula has a maximum at V
IN
= 2V
OUT
, where I
RMS
=
I
OUT
/2. This simple worst case is commonly used for design
because even significant deviations do not offer much relief.
Note that ripple current directly affects capacitor’s lifetime.
DO NOT UNDERSPECIFY THIS COMPONENT. An additional
0.1µF ceramic capacitor is also required on V
IN
for high
frequency decoupling.
C
OUT
To avoid overheating, the output capacitor must be sized to
handle the ripple current generated by the inductor. The
worst case RMS ripple current in the output capacitor is
given by:
IIA
mA
RMS PEAK RMS
≈
()
=
2
170
or 300mA
Although the output voltage ripple is determined by the
hysteresis of the voltage comparator, ESR of the output
capacitor is also a concern. Too high of an ESR will create
a higher ripple output voltage and at the same time cause the
LTC1174 to sleep less often. This will affect the efficiency of
the LTC1174. For a given technology, ESR is a direct
function of the volume of the capacitor. Several small-sized
capacitors can also be paralleled to obtain the same ESR as
one large can. Manufacturers such as Nichicon, Chemicon
and Sprague should be considered for high performance
capacitors. The OS-CON semiconductor dielectric capaci-
tor available from Sanyo has the lowest ESR for its size, at
a higher price.
9
LTC1174
LTC1174-3.3/LTC1174-5
1174fe
Catch Diode Selection
The catch diode carries load current during the off-time. The
average diode current is therefore dependent on the
P-channel switch duty cycle. At high input voltages the
diode conducts most of the time. As V
IN
approaches V
OUT
the diode conducts only a small fraction of the time. The
most stressful condition for the diode is when the output is
short-circuited. Under this condition the diode must safely
handle I
PEAK
at close to 100% duty cycle. A fast switching diode
must also be used to optimize efficiency. Schottky diodes are
a good choice for low forward drop and fast switching times.
Most LTC1174 circuits will be well served by either a 1N5818,
a MBRS140T3 or a MBR0520L Schottky diode.
Short-Circuit Protection
The LTC1174 is protected from output short by its internal
current limit. Depending on the condition of I
PGM
pin, the
limit is either set to 340mA or 600mA. In addition, the off-
time of the switch is increased to allow the inductor’s
current to decay far enough to prevent any current build-up
(see Figure 2).
APPLICATIO S I FOR ATIO
WUUU
compared with a 1.25V reference voltage. With the current
going into Pin 3 being negligible, the following expression
is used for setting the trip limit:
VR
R
LBTRIP
=+
⎛
⎝
⎜⎞
⎠
⎟
125 1 4
3
.
When the LTC1174 is shut down, the low-battery detector
is inactive.
I
PGM
= V
IN
I
PGM
= 0
GND
L = 100µH
V
IN
= 13.5V
20µs/DIV 1174 F02
Figure 2. Inductor's Current with Output Shorted
Low-Battery Detector
The low-battery indicator senses the input voltage through
an external resistive divider. This divided voltage connects
to the “–” input of a voltage comparator (Pin 3) which is
Figure 3. Low-Battery Comparator
LTC1174
–
+
1.25V
REFERENCE
R4
R3
3
V
IN
1174 F03
LTC1174 Adjustable/Low Noise Applications
The LTC1174 develops a 1.25V reference voltage between
the feedback (Pin 1) terminal and ground (see Figure 4). By
selecting resistor R1, a constant current is caused to flow
through R1 and R2 to set the overall output voltage. The
regulated output voltage is determined by:
VR
R
OUT
=+
⎛
⎝
⎜⎞
⎠
⎟
125 1 2
1
.
For most applications, a 30k resistor is suggested for R1.
To prevent stray pickup, a 100pF capacitor is suggested
across R1 located close to the LTC1174. Alternatively, a
capacitor across R2 can be used to increase the switching
frequency for low noise operation.
Inverting Applications
The LTC1174 can easily be set up for a negative output
voltage. If –5V is desired, the LTC1174-5 is ideal for this
application as it requires the least components. Figure 5
shows the schematic for this application. Note that the
10
LTC1174
LTC1174-3.3/LTC1174-5
1174fe
APPLICATIO S I FOR ATIO
WUUU
output voltage is now taken off the GND pin. Therefore,
the maximum input voltage is now determined by the
difference between the absolute maximum voltage rating
and the output voltage. A maximum of 12V is specified in
Figure 5, giving the circuit a 1.5V of headroom for V
IN
. Note
that the circuit can operate from a minimum of 4V, making
it ideal for a 4 NiCad cell application. For a higher output
current circuit, please refer to the Typical Applications
section.
Absolute Maximum Ratings and Latchup Prevention
The absolute maximum ratings specify that SW (Pin 5) can
never exceed V
IN
(Pin 6) by more than 0.3V. Normally this
situation should never occur. It could, however, if the
output is held up while the supply is pulled down. A con-
dition where this could potentially occur is when a battery
is supplying power to an LTC1174/LTC1174-3.3/
LTC1174-5 regulator and also to one or more loads in
parallel with the the regulator’s V
IN
. If the battery is dis-
connected while the LTC1174/LTC1174-3.3/LTC1174-5
regulator is supplying a light load and one of the parallel
circuits is a heavy load, the input capacitor of the LTC1174/
LTC1174-3.3/LTC1174-5 regulator could be pulled down
faster than the output capacitor, causing the absolute
maximum ratings to be exceeded. The result is often a
latchup which can be destructive if V
IN
is reapplied. Bat-
tery disconnect is possible as a result of mechanical stress,
bad battery contacts or use of a lithium-ion battery with
a built-in internal disconnect. The user needs to assess
his/her application to determine whether this situation
could occur. If so, additional protection is necessary.
Prevention against latchup can be accomplished by sim-
ply connecting a Schottky diode across the SW and V
IN
pins as shown in Figure 6. The diode will normally be
reverse biased unless V
IN
is pulled below V
OUT
at which
time the diode will clamp the (V
OUT
– V
IN
) potential to less
than the 0.6V required for latchup. Note that a low leakage
Schottky should be used to minimize the effect on no-load
supply current. Schottky diodes such as MBR0530, BAS85
and BAT84 work well. Another more serious effect of the
protection diode leakage is that at no load with nothing to
provide a sink for this leakage current, the output voltage
can potentially float above the maximum allowable toler-
ance. To prevent this from occuring, a resistor must be
connected between V
OUT
and ground with a value low
enough to sink the maximum possible leakage current.
Figure 4. LTC1174 Adjustable Configuration
R2
R1
1
VOUT
1174 F04
100pF*
6.8nF**
*
**
ADJUSTABLE APPLICATIONS
LOW NOISE APPLICATIONS
LTC1174 VFB
Figure 5. Positive-to-Negative 5V Converter
3SHUTDOWN
2
7
6
8
1
5
4
50µH**
VOUT
–5V
45mA
MBRS140T3
1174 F05
*
**
AVX TPSD476K016
COILTRONICS CTX50-4
INPUT VOLTAGE
4V TO 12V
0.1µF
47µF*
16V
×2
47µF*
16V
×2
LTC1174HV-5
LBIN
LBOUT
IPGM
GND
VIN
VOUT
SW
+
+
Figure 6. Preventing Absolute Maximum
Ratings from Being Exceeded
1174 F06
VIN VOUT
LATCHUP
PROTECTION
SCHOTTKY
SW
LTC1174
LTC1174-3.3
LTC1174-5
+
11
LTC1174
LTC1174-3.3/LTC1174-5
1174fe
Figure 7. LTC1174 Layout Diagram (See Board Layout Checklist)
APPLICATIO S I FOR ATIO
WUUU
Board Layout Checklist
When laying out the printed circuit board, the following
checklist should be used to ensure proper operation of the
LTC1174. These items are also illustrated graphically in
the layout diagram in Figure 7. Check the following in your
layout:
1. Is the Schottky catch diode
closely
connected between
ground (Pin 4) and switch (Pin 5)?
2. Is the “+” plate of C
IN
closely
connected to V
IN
(Pin 6)?
This capacitor provides the AC current to the internal
P-channel MOSFET.
3. Is the 0.1µF V
IN
decoupling capacitor
closely
conected
between V
IN
(Pin 6) and ground (Pin 4)? This capacitor
carries the high frequency peak currents.
4. Is the SHUTDOWN (Pin 8) actively pulled to V
IN
during
normal operation? The SHUTDOWN pin is high imped-
ance and must not be allowed to float.
5. Is the I
PGM
(Pin 7) pulled either to V
IN
or ground? The
I
PGM
pin is high impedance and must not be allowed
to float.
3
LTC1174
2
SW
R1
8
7
6
1
54
L
VOUT
D
1174 F07
OUTPUT DIVIDER
REQUIRED WITH
ADJUSTABLE
VERSION ONLY 0.1µF
LBOUT
LBIN
GND
SHUTDOWN
IPGM
VIN
R2
BOLD LINES INDICATE
HIGH CURRENT PATH
VIN
CIN
COUT
VOUT
(VFB)
+
+
DESIGN EXAMPLE
As a design example, assume V
IN
= 9V (nominal), V
OUT
=
5V, and I
OUT
= 350mA maximum. The LTC1174-5 is used
for this application, with I
PGM
(Pin 7) connected to V
IN
. The
minmum value of L is determined by assuming the
LTC1174-5 is operating in continuous mode.
Figure 8. Continuous Inductor Current
INDUCTOR CURRENT
TIME
I
PEAK
I
V
AVG CURRENT = I
OUT
=
= 350mA
I
PEAK
+ I
V
2
1174 F08
With I
OUT
= 350mA and I
PEAK
= 0.6A (I
PGM
= V
IN
), I
V
=
0.1A.The peak-to-peak ripple inductor current, I
RIPPLE
, is
0.5A and is also equal to:
IVV
LA
RIPPLE OUT D PP
=+
⎛
⎝
⎜⎞
⎠
⎟
()
−−
410
6
•
12
LTC1174
LTC1174-3.3/LTC1174-5
1174fe
APPLICATIO S I FOR ATIO
WUUU
Solving for L in the above equation and with V
D
= 0.6V,
L = 44.8µH. The next higher standard value of L is 50µH
(example: Coiltronics CTX50-4). The operating frequency,
neglecting voltage across diode V
D
is:
fV
V
kHz
OUT
IN
≈−
⎛
⎝
⎜⎞
⎠
⎟
=
2 5 10 1
111
5
.•
With the value of L determined, the requirements for C
IN
and C
OUT
are calculated. For C
IN
, its RMS current rating
should be at least:
IIVVV
VA
mA
RMS
OUT OUT IN OUT
IN RMS
=−
()
[]
()
=
12
174
/
For C
OUT
, the RMS current rating should be at least:
IIA
mA
RMS PEAK RMS
≈
()
=
2
300
Now allow V
IN
to drop to 6V. At this minimum input voltage
the operating frequency will decrease. The new frequency
is 42kHz.
Table 1. Inductor Manufacturers
MANUFACTURER PART NUMBER
Coilcraft DT3316 Series
1102 Silver Lake Road
Cary, IL 60013
(708) 639-2361
Coiltronics Inc. Econo-Pac
6000 Park of Commerce Blvd. Octa-Pac
Boca Raton, FL 33487
(407) 241-7876
Gowanda Electronics Corporation GA10 Series
1 Industrial Place
Gowanda, NY 14070
(716) 532-2234
Sumida Electric Co. Ltd. CD 54 Series
637 E. Golf Road, Suite 209 CD 75 Series
Arlington Heights, IL 60005
(708) 956-0666/7
Table 2. Capacitor Manufacturers
MANUFACTURER PART NUMBER
AVX Corporation TPS Series
P.O. Box 887 TAJ Series
Myrtle Beach, SC 29578
(803) 448-9411
Nichicon America Corporation PL Series
927 East State Parkway
Schaberg, IL 60173
(708) 843-7500
Sanyo Video Components OS-CON Series
2001 Sanyo Avenue
San Diego, CA 92173
(619) 661-6385
Attn: Sales Dept.
13
LTC1174
LTC1174-3.3/LTC1174-5
1174fe
TYPICAL APPLICATIO S
U
High Efficiency 3.3V Regulator
6V to 5V Step-Down Regulator with Low-Battery Detection
1174 TA03
INPUT VOLTAGE
6V
3LTC1174-5
LBIN
LBOUT
IPGM
GND
VIN
SHUTDOWN
VOUT
SW
2
7
6
8
1
5
4
L1†
100µH
VOUT
5V
365mA
47µF**
16V
×2
D1
0.1µF
*LOW-
BATTERY
INDICATOR
4.7k
162k
47.5k
*
**
D1
†
LOW-BATTERY INDICATOR
IS SET TO TRIP AT VIN = 5.5V
AVX TPSD476K016
= MBRS140T3 (SURFACE MOUNT)
1N5818
L1 SELECTION
MANUFACTURER
COILTRONICS
SUMIDA
GOWANDA
PART NO.
CTX100-4
CD75-101
GA10-103K
TYPE
SURFACE MOUNT
SURFACE MOUNT
THROUGH HOLE
+
47µF**
16V
×2
+
1174 TA04
3
LTC1174-3.3
LB
IN
LB
OUT
I
PGM
GND
V
IN
SHUTDOWN
V
OUT
SW
2
7
6
8
1
5
4
50µH
†
V
OUT
3.3V
425mA
22µF*
25V
×3
1N5818
0.1µF
47µF**
16V
×2
INPUT VOLTAGE
4V TO 12.5V
*
**
†
AVX TPSD226K025
AVX TPSD476K016
COILTRONICS CTX50-4
+
+
14
LTC1174
LTC1174-3.3/LTC1174-5
1174fe
Low Noise 3V Regulator
Positive-to-Negative (–5V) Converter
TYPICAL APPLICATIO S
U
1174 TA05
3
LTC1174
LB
IN
LB
OUT
I
PGM
GND
V
IN
SHUTDOWN
V
FB
SW
2
7
6
8
1
5
4
50µH
†
V
OUT
3V
450mA
22µF*
25V
×3
1N5818
0.1µF
100µF**
10V
×2
INPUT VOLTAGE
4V TO 12.5V
*
**
†
AVX TPSD226K025
AVX TPSD105K010
COILTRONICS CTX50-4
42k
30k
6.8nF
+
+
*
**
***
D1
†
LOW-BATTERY INDICATOR
IS SET TO TRIP AT V
IN
= 4.4V
AVX TPSD106K035
AVX TPSD105K010
= MBRS130LT3 (SURFACE MOUNT)
1N5818
L1 SELECTION
MANUFACTURER
COILTRONICS
COILCRAFT
SUMIDA
GOWANDA
PART NO.
CTX50-3
DT3316-473
CD54-470
GA10-472K
TYPE
SURFACE MOUNT
SURFACE MOUNT
SURFACE MOUNT
THROUGH HOLE
1174 TA06
INPUT VOLTAGE
4V TO 12.5V
3LTC1174HV-5
LB
IN
LB
OUT
I
PGM
GND
V
IN
SHUTDOWN
V
OUT
SW
2
7
6
8
1
5
4
L1
†
50µH
V
OUT
–5V
10µF**
35V
×2
D1
0.1µF
100µF***
10V
*LOW-
BATTERY
INDICATOR
4.7K
280k
43k
V
IN
(V)
4
6
8
10
12.5
I
OUT MAX
(mA)
110
140
170
200
235
+
+
15
LTC1174
LTC1174-3.3/LTC1174-5
1174fe
Positive-to-Negative (– 3.3V) Converter
Negative Boost Converter
1174 TA07
INPUT VOLTAGE
4V TO 13.5V
3LTC1174HV-3.3
LB
IN
LB
OUT
I
PGM
GND
V
IN
SHUTDOWN
V
OUT
SW
2
7
6
8
1
5
4
L1
†
50µH
V
OUT
–3.3V
210mA
33µF**
20V
×2
D1
0.1µF
100µF***
10V
×2
*LOW-
BATTERY
INDICATOR
4.7K
220k
43k
*
**
***
D1
†
LOW-BATTERY INDICATOR
IS SET TO TRIP AT V
IN
= 4.4V
AVX TPSD336K020
AVX TPSD105K010
= MBRS140T3 (SURFACE MOUNT)
1N5818
L1 SELECTION
MANUFACTURER
COILTRONICS
COILCRAFT
SUMIDA
GOWANDA
PART NO.
CTX50-3
DT3316-473
CD54-470
GA10-472K
TYPE
SURFACE MOUNT
SURFACE MOUNT
SURFACE MOUNT
THROUGH HOLE
I
OUT MAX
(mA)
175
205
230
255
V
IN
(V)
4
5
6
7
+
+
1174 TA08
INPUT VOLTAGE
–5V
3LTC1174-3.3
LBIN
LBOUT
IPGM
GND
VIN
SHUTDOWN
VOUT
SW
2
7
6
8
1
5
4
L1†
50µHVOUT
–9V
175mA
33µF*
16V
×2D1
0.1µF
33µF*
20V
×2
310k
50k
*
D1
†
AVX TPSD336K020
= MBRS140T3 (SURFACE MOUNT)
1N5818
L1 SELECTION
0.1µF
MANUFACTURER
COILTRONICS
COILCRAFT
SUMIDA
GOWANDA
PART NO.
CTX50-3
DT3316-473
CD54-470
GA10-472K
TYPE
SURFACE MOUNT
SURFACE MOUNT
SURFACE MOUNT
THROUGH HOLE +
+
TYPICAL APPLICATIO S
U
16
LTC1174
LTC1174-3.3/LTC1174-5
1174fe
LCD Display Power Supply
9V to 5V Pre-Post Regulator
1174 TA09
INPUT
VOLTAGE
6V TO 12.5V
3
LTC1174
LB
IN
LB
OUT
I
PGM
GND
V
IN
SHUTDOWN
V
FB
SW
2
7
6
8
1
5
4
L1
†
50µH
V
OUT
5V
150mA
D1
1µF
SOLID
TANTALUM
47µF**
16V, ×2
110k
††
0.1µF
*
**
D1
†
SANYO OS-CON
AVX TPSD476K016
= MBRS140T3 (SURFACE MOUNT)
1N5818
L1 SELECTION
MANUFACTURER
COILTRONICS
COILCRAFT
SUMIDA
GOWANDA
PART NO.
CTX50-3
DT3316-473
CD54-470
GA10-472K
TYPE
SURFACE MOUNT
SURFACE MOUNT
SURFACE MOUNT
THROUGH HOLE
††
USE 1% METAL FILM RESISTORS
30.1k
††
LT
®
1121-5
OUT
GND
81
5
V
IN
SHUTDOWN
3
0.1µF
100µF*
16V
100pF
+
++
1174 TA10
INPUT
VOLTAGE
4V TO 12.5V
3
LTC1174
LB
IN
LB
OUT
I
PGM
GND
V
IN
SHUTDOWN
V
FB
SW
2
7
6
8
1
5
4
L1†
100µH
V
OUT
–24V
50mA AT
V
IN
= 9V
47µF**
16V
×2
0.1µF
10µF*
50V
×4
1N914
998k††
V
IN
(V)
4
5
6
7
8
9
10
11
12
I
OUT MAX
(mA)
20
25
30
35
43
50
55
60
65
Si9435
D1
50k††
56.2k††
0.1µF
*
**
D1
†
AVX TAJE106K050
AVX TPSD476K016
= MBRS140T3 (SURFACE MOUNT)
1N5818
L1 SELECTION
MANUFACTURER
COILTRONICS
COILCRAFT
SUMIDA
GOWANDA
PART NO.
CTX100-3
DT3316-104
CD75-101
GA10-103K
TYPE
SURFACE MOUNT
SURFACE MOUNT
SURFACE MOUNT
THROUGH HOLE
††
USE 1% METAL FILM RESISTORS
2N2222
2N5210
+
+
TYPICAL APPLICATIO S
U
17
LTC1174
LTC1174-3.3/LTC1174-5
1174fe
9V to 5V, –5V Outputs
9V to 12V, –12V Outputs
TYPICAL APPLICATIO S
U
1174 TA11
INPUT VOLTAGE
4V TO 12.5V
3
LTC1174HV-5
LB
IN
LB
OUT
I
PGM
GND
V
IN
SHUTDOWN
V
OUT
SW
2
7
6
8
1
5
4L1B
†
100µH
–V
OUT
–5V
135mA AT
V
IN
= 9V
3.3µF**
100µF*
16V
MBRS140T3
L1A
†
100µH
V
OUT
5V
135mA AT
V
IN
= 9V
0.1µF0.1µF
*
**
†
SANYO OS-CON
WIMA MKS2
COILTRONICS CTX100-4
V
IN
(V)
4
6
8
10
12
13
I
OUT MAX
(mA)
75
100
125
145
160
180
100µF*
20V
100µF*
16V
L1A
L1B
23
41
CTX100-4
MBRS140T3
+
+
+
1174 TA12
INPUT VOLTAGE
4V TO 12.5V
3
LTC1174
LB
IN
LB
OUT
I
PGM
GND
V
IN
SHUTDOWN
V
FB
SW
2
7
6
8
1
5
4L1B†
100µH
–V
OUT
–12V
55mA AT
V
IN
= 9V
3.3µF**
1N914
Si9430DY
MBRS140T3
MBRS140T3
L1A†
100µH
12
4
3
V
OUT
12V
55mA AT
V
IN
= 9V
0.1µF
*
**
†
††
AVX TAJD226K035
WIMA MKS2
COILTRONICS CTX100-4
USE 1% METAL FILM RESISTORS
V
IN
(V)
4
5
6
7
8
9
10
11
12
I
OUT MAX
(mA)
20
25
35
45
50
55
62
67
73
22µF*
35V
×3L1A
L1B
23
41
CTX100-4
301k††
22µF*
35V
×2
34k††
+
+
22µF*
35V
×2
+
18
LTC1174
LTC1174-3.3/LTC1174-5
1174fe
Automatic Current Selection
Buck-Boost Converter
TYPICAL APPLICATIO S
U
1174 TA13
INPUT
VOLTAGE
6V TO 12.5V
3LTC1174-5
LBIN
LBOUT
IPGM
GND
VIN
SHUTDOWN
VOUT
SW
2
7
6
8
1
5
4
50µH†VOUT
5V
0mA TO
320mA
100µF*
20V
100µF*
16V
1N5818
100k
*
†
SANYO OS-CON CAPACITOR
COILTRONICS CTX50-4
0.1µF
100k
36.5k
TPO610L
100k
+
+
1174 TA14
INPUT VOLTAGE
4V TO 12V
3
LTC1174HV-5
LB
IN
LB
OUT
I
PGM
GND
V
IN
SHUTDOWN
V
OUT
SW
2
7
6
8
1
5
4
3.3µF**
L1A
†
100µH
12
L2A
†
100µH
4
3
V
OUT
5V
160mA
0.1µF
*
**
†
SANYO OS-CON
WIMA MKS2
COILTRONICS CTX100-4
100µF*
20V
L1A
L1B
23
41
CTX100-4 100µF*
16V
1N5818
+
+
19
LTC1174
LTC1174-3.3/LTC1174-5
1174fe
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.
U
PACKAGE DESCRIPTIO
N8 Package
8-Lead PDIP (Narrow .300 Inch)
(Reference LTC DWG # 05-08-1510)
S8 Package
8-Lead Plastic Small Outline (Narrow .150 Inch)
(Reference LTC DWG # 05-08-1610)
N8 1002
.065
(1.651)
TYP
.045 – .065
(1.143 – 1.651)
.130 ± .005
(3.302 ± 0.127)
.020
(0.508)
MIN
.018 ± .003
(0.457 ± 0.076)
.120
(3.048)
MIN
.008 – .015
(0.203 – 0.381)
.300 – .325
(7.620 – 8.255)
.325 +.035
–.015
+0.889
–0.381
8.255
()
12 34
87 65
.255 ± .015*
(6.477 ± 0.381)
.400*
(10.160)
MAX
NOTE:
1. DIMENSIONS ARE INCHES
MILLIMETERS
*THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS.
MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED .010 INCH (0.254mm)
.100
(2.54)
BSC
.016 – .050
(0.406 – 1.270)
.010 – .020
(0.254 – 0.508)× 45°
0°– 8° TYP
.008 – .010
(0.203 – 0.254)
SO8 0303
.053 – .069
(1.346 – 1.752)
.014 – .019
(0.355 – 0.483)
TYP
.004 – .010
(0.101 – 0.254)
.050
(1.270)
BSC
1234
.150 – .157
(3.810 – 3.988)
NOTE 3
8765
.189 – .197
(4.801 – 5.004)
NOTE 3
.228 – .244
(5.791 – 6.197)
.245
MIN .160 ±.005
RECOMMENDED SOLDER PAD LAYOUT
.045 ±.005
.050 BSC
.030 ±.005
TYP
INCHES
(MILLIMETERS)
NOTE:
1. DIMENSIONS IN
2. DRAWING NOT TO SCALE
3. THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS.
MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED .006" (0.15mm)
20
LTC1174
LTC1174-3.3/LTC1174-5
1174fe
© LINEAR TECHNOLOGY CORPORATION 1994
LT 1006 REV E • PRINTED IN USA
Battery Charger
RELATED PARTS
PART NUMBER DESCRIPTION COMMENTS
LT®1074/LT1076 Step-Down Switching Regulator 100kHz, 5A (LT1074) or 2A (LT1076) Monolithic
LTC1147 High Efficiency Step-Down DC/DC Controller 8-Pin Controller
LTC1265 1.2A High Efficiency Step-Down DC/DC Regulator Burst Mode Operation, Monolithic
LT1375/LT1376 1.5A 500kHz Step-Down Switching Regulator High Frequency Small Inductor
LTC1574 High Efficiency Step-Down DC/DC Regulator LTC1174 with Internal Schottky Diode
LT1611 Inverting 1.4MHz Switching Regulator in SOT-23 – 5V at 150mA from 5V Input, 1mV
P-P
Output Ripple, SOT-23 Package
LTC1701 1MHz Step-Down DC/DC Converter in SOT-23 V
IN
= 2.5V to 5.5V, I
Q
= 135µA, V
OUT
= 5V to 1.25V
LTC1707 High Efficiency Synchronous Step-Down Regulator V
IN
= 2.85 to 8.5V, Selectable Burst Mode Operation,
600mA Output Current, SO-8 Package
LTC1877 High Efficiency Synchronous Step-Down Regulator 600mA at V
IN
= 5V, 2.65V to 10V = V
IN
, I
Q
= 10µA
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900
●
FAX: (408) 434-0507
●
www.linear.com
TYPICAL APPLICATIO
U
1174 TA15
INPUT VOLTAGE
8V TO 12.5V
3
LTC1174
LB
IN
LB
OUT
I
PGM
GND
V
IN
SHUTDOWN
V
FB
SW
2
7
6
8
1
5
4D1
L1†
50µH
V
OUT
TO
4 NiCAD BATTERY
0.1µF
100µF**
10V
33k
150k
V
IN
(V)
8
9
10
11
12
I
OUT MAX
(mA)
320
325
330
335
335
*
**
D1,D2
†
AVX TAJD226K020
AVX TAJD107K010
= MBRS140T3
(SURFACE MOUNT)
1N5818
L1 SELECTION
MANUFACTURER
COILTRONICS
COILCRAFT
SUMIDA
GOWANDA
PART NO.
CTX50-2P
DT3316-473
CD54-470
GA10-472K
TYPE
SURFACE MOUNT
SURFACE MOUNT
SURFACE MOUNT
THROUGH HOLE
22µF*
20V
×2
D2
+
+
