LTC1174
LTC1174-3.3/LTC1174-5
High Efficiency
Step-Down and Inverting
DC/DC Converter
FEATURES
s
s
DESCRIPTIO
s
s
s
s
s
s
s
s
s
s
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
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.
and LTC are registered trademarks and LT is a trademark of Linear Technology Corporation.
APPLICATIO S
s
s
s
s
s
s
Distributed Power Systems
Step-Down Converters
Inverting Converters
Memory Backup Supply
Portable Instruments
Battery-Powered Equipment
TYPICAL APPLICATIO
V
IN
9V
3
2
7
High Efficiency Step-Down Converter
100
LTC1174-5 Efficiency
6
V
IN
LB
IN
LB
OUT
I
PGM
LTC1174-5
GND
4
SHUTDOWN
V
OUT
SW
8
1
5
100µH
1N5818
†
+
EFFICIENCY (%)
15µF*
25V
×3
95
V
IN
= 6V
90
85
80
75
L = 100µH
V
OUT
= 5V
I
PGM
= 0V
1
10
LOAD CURRENT (mA)
100 200
1174 TA02
5V
175mA
+
100µF**
10V
1174 TA01
* (3) AVX TPSD156K025
** AVX TPSD107K010
†
COILTRONICS CTX100-4
70
U
V
IN
= 9V
U
U
1
LTC1174
LTC1174-3.3/LTC1174-5
ABSOLUTE
AXI U
RATI GS
(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
PACKAGE/ORDER I FOR ATIO
ORDER PART
NUMBER
TOP VIEW
V
OUT
(V
FB
*) 1
LB
OUT
2
LB
IN
3
GND 4
N8 PACKAGE
8-LEAD PDIP
* ADJUSTABLE OUTPUT VERSION
T
JMAX
= 125°C,
θ
JA
= 110°C/W
8
7
6
5
SHUTDOWN
I
PGM
V
IN
SW
LTC1174CN8
LTC1174CN8-3.3
LTC1174CN8-5
LTC1174IN8
LTC1174HVCN8
LTC1174HVCN8-3.3
LTC1174HVCN8-5
Consult factor for Military grade parts.
ELECTRICAL CHARACTERISTICS
SYMBOL PARAMETER
I
FB
V
FB
V
OUT
∆V
OUT
Feedback Current
Feedback Voltage
Regulated Output Voltage
Output Voltage Line Regulation
Output Voltage Load Regulation
CONDITIONS
The
q
denotes specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 9V, V
SHUTDOWN
= V
IN
, I
PGM
= 0V, unless otherwise noted.
MIN
q
q
q
LTC1174/LTC1174HV
LTC1174/LTC1174HV
LTC1174-3.3/LTC1174HV-3.3
LTC1174-5/LTC1174V-5
V
IN
= 6V to 12V, I
LOAD
= 100mA, I
PGM
= V
IN
(Note 3)
LTC1174-3.3 (Note 3)
20mA < I
LOAD
< 175mA, I
PGM
= 0V
20mA < I
LOAD
< 400mA, I
PGM
= V
IN
LTC1174-5 (Note 3)
20mA < I
LOAD
< 175mA, I
PGM
= 0V
20mA < I
LOAD
< 400mA, I
PGM
= V
IN
1.20
3.14
4.75
1.25
3.30
5.00
10
–5
–45
–5
–50
2
U
U
W
W W
U
W
(Note 1)
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
TOP VIEW
V
OUT
(V
FB
*) 1
LB
OUT
2
LB
IN
3
GND 4
8
7
6
5
SHUTDOWN
I
PGM
V
IN
SW
S8 PACKAGE
8-LEAD PLASTIC SO
* ADJUSTABLE OUTPUT VERSION
T
JMAX
= 125°C,
θ
JA
= 150°C/W
LTC1174CS8
LTC1174CS8-3.3
LTC1174CS8-5
LTC1174IS8
LTC1174HVCS8
LTC1174HVCS8-3.3
LTC1174HVCS8-5
LTC1174HVIS8
S8 PART MARKING
1174
117433
117450
1174I
1174HV
1174H3
1174H5
1174HI
TYP
MAX
1
1.30
3.46
5.25
70
–70
–70
–70
–70
UNITS
µA
V
V
V
mV
mV
mV
mV
mV
LTC1174
LTC1174-3.3/LTC1174-5
ELECTRICAL CHARACTERISTICS
SYMBOL PARAMETER
I
Q
Input DC Supply Current (Note 4)
The
q
denotes specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 9V, V
SHUTDOWN
= V
IN
, I
PGM
= 0V, unless otherwise noted.
CONDITIONS
Active Mode
LTC1174: 4V < V
IN
< 12V, I
PGM
= 0V
LTC1174HV: 4V < V
IN
< 16V, I
PGM
= 0V
Sleep Mode
LTC1174: 4V < V
IN
< 12V
LTC1174HV: 4V < V
IN
< 16V
SHUTDOWN (Note 4)
LTC1174: V
SHUTDOWN
= 0V, 4V < V
IN
< 12V
LTC1174HV: V
SHUTDOWN
= 0V, 4V < V
IN
< 16V
MIN
TYP
450
450
130
130
1
2
1.25
1.0
0.6
7.5
0.54
0.27
1.2
0.8
15
0.60
0.34
0.75
0.90
4
MAX
600
600
180
180
10
25
1.4
0.5
1.5
1.5
30
0.78
0.50
1.30
1.55
5
0.75
0.5
2.0
0.5
UNITS
µA
µA
µA
µA
µA
µA
V
µA
mA
mA
mV
A
A
Ω
Ω
µs
V
V
µA
µA
µA
V
LBTRIP
I
LBIN
I
LBOUT
V
HYST
I
PEAK
R
ON
t
OFF
V
IH
V
IL
I
IH
I
IL
Low-Battery Trip Point
Current into Pin 3
Current Sunk by Pin 2
Comparator Hysteresis
Current Limit
ON Resistance of Switch
Switch Off-Time (Note 6)
SHUTDOWN Pin High
SHUTDOWN Pin Low
SHUTDOWN Pin Input Current
SHUTDOWN Pin Input Current
LTC1174: V
LBOUT
= 0.4V
LTC1174HV: V
LBOUT
= 0.4V
LTC1174/LTC1174HV
I
PGM
= V
IN
, V
OUT
= 0V
I
PGM
= 0V, V
OUT
= 0V
LTC1174
LTC1174HV
V
OUT
at Regulated Value
Minimum Voltage at Pin 8 for Device to Be Active
Maximum Voltage at Pin 8 for Device to Be in Shutdown
LTC1174: V
SHUTDOWN
= 12V
LTC1174HV: V
SHUTDOWN
= 16V
0
≤
V
SHUTDOWN
≤
0.8V
q
q
q
q
3
1.2
The
q
denotes specifications which apply over the full operating temperature range,
otherwise specifications are at – 40°C
≤
T
A
≤
85°C. LTC1174I and LTC1174HVI Only.
SYMBOL PARAMETER
V
FB
Feedback Voltage
I
LBOUT
Current Sunk by Pin 2
I
PEAK
Current Limit
CONDITIONS
LTC1174I/LTC1174HVI
V
LBOUT
= 0.4V (LTC1174I)
V
LBOUT
= 0.4V (LTC1174HVI)
I
PGM
= V
IN
, V
OUT
= 0V (LTC1174I)
I
PGM
= 0V, V
OUT
= 0V (LTC1174I)
I
PGM
= V
IN
, V
OUT
= 0V (LTC1174HVI)
I
PGM
= 0V, V
OUT
= 0V (LTC1174HVI)
V
OUT
at Regulated Value (LTC1174I)
V
OUT
at Regulated Value (LTC1174HVI)
LTC1174I/LTC1174HVI
q
q
q
q
q
q
q
q
MIN
1.18
0.75
0.50
0.54
0.5
2.0
1.8
t
OFF
R
ON
Switch Off-Time (Note 6)
Switch On Resistance
TYP
1.25
1.2
0.8
0.60
0.34
0.60
0.34
4
4
0.9
MAX
1.31
2.0
1.6
0.78
0.8
6.0
6.2
1.7
UNITS
V
mA
mA
A
A
A
A
µs
µs
Ω
Note 1:
Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
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)
Note 3:
Guaranteed by design.
Note 4:
Dynamic supply current is higher due to the gate charge being
delivered at the switching frequency.
Note 5:
Current into Pin 6 only, measured without electrolytic input
capacitor.
Note 6:
The off-time is wafer-sort trimmed.
3
LTC1174
LTC1174-3.3/LTC1174-5
TYPICAL PERFOR A CE CHARACTERISTICS
Efficiency vs Load Current
100
95
100
95
V
IN
= 6V
EFFICIENCY (%)
EFFICIENCY (%)
V
IN
= 9V
85
80
75
70
EFFICIENCY (%)
90
L = 50µH
V
OUT
= 5V
I
PGM
= 0V
COIL = CTX50-4
1
10
LOAD CURRENT (mA)
100 200
1174 G01
Efficiency vs Load Current
100
V
IN
= 5V
100
90
EFFICIENCY (%)
EFFICIENCY (%)
80
80
V
IN
= 9V
EFFICIENCY (%)
V
IN
= 9V
70
L = 50µH
V
OUT
= 3.3V
I
PGM
= 0V
COIL = CTX50-4
1
10
100
LOAD CURRENT (mA)
300
1174 G04
60
50
Line Regulation
6
4
2
I
LOAD
= 100mA
I
PGM
= 0V
180
160
LEAKAGE CURRENT (nA)
0
EFFICIENCY (%)
∆V
OUT
(mV)
–2
–4
–6
–8
–10
–12
–14
0
2
8
4
10
6
INPUT VOLTAGE (V)
12
14
Kool Mµ is a registered trademark of Magnetics, Inc.
4
U W
1174 G07
Efficiency vs Load Current
100
95
V
IN
= 6V
V
IN
= 9V
85
80
75
70
1
10
100
LOAD CURRENT (mA)
400
1174 G02
Efficiency vs Load Current
V
IN
= 6V
90
V
IN
= 9V
85
80
75
70
1
10
100
LOAD CURRENT (mA)
500
1174 G03
90
L = 50µH
V
OUT
= 5V
I
PGM
= V
IN
COIL = CTX50-4
L = 100µH
V
OUT
= 5V
I
PGM
= V
IN
COIL = CTX100-4
Efficiency vs Load Current
100
V
IN
= 5V
Efficiency vs Load Current
90
90
V
IN
= 5V
80
V
IN
= 9V
70
L = 100µH
V
OUT
= 3.3V
I
PGM
= V
IN
COIL = CTX100-4
1
10
100
LOAD CURRENT (mA)
500
1174 G06
70
L = 100µH
V
OUT
= 3.3V
I
PGM
= V
IN
COIL = CTX100-4
1
10
100
LOAD CURRENT (mA)
500
1174 G06
60
60
50
50
Switch Leakage Current
vs Temperature
95
V
IN
= 13.5V
94
93
92
91
90
89
88
87
0
20
40
60
TEMPERATURE (°C)
80
100
1174 G08
Efficiency vs Input Voltage
140
120
100
80
60
40
20
0
L = 100µH
L = 50µH
V
OUT
= 5V
I
PGM
= 0V
I
LOAD
= 75mA
CORE = CTX (Kool Mµ
®
)
5
6
7
9 10 11 12
8
INPUT VOLTAGE (V)
13
14
1174 G09
LTC1174
LTC1174-3.3/LTC1174-5
TYPICAL PERFOR A CE CHARACTERISTICS
Efficiency vs Input Voltage
95
94
93
92
91
90
I
LOAD
= 100mA
I
PGM
= 0V
V
OUT
= 5V
L = 100µH
COIL = CTX100-4
SUPPLY CURRENT (µA)
SUPPLY CURRENT (µA)
EFFICIENCY (%)
I
LOAD
= 300mA
I
PGM
= V
IN
89
5
6
7
8
9 10 11 12
INPUT VOLTAGE (V)
13
14
Operating Frequency
vs V
IN
– V
OUT
2.0
V
OUT
= 5V
1.7
1.6
1.5
1.5
1.4
NORMALIZED FREQUENCY
OFF-TIME (µs)
RDS
(ON)
(Ω)
T
A
= 25°C
1.0
T
A
= 70°C
0.5
0
0
1
5
7
3
6
2
4
(V
IN
– V
OUT
) VOLTAGE (V)
8
9
PI FU CTIO S
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.
SW(Pin5):
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.
U W
1174 G10
1174 G13
Supply Current in Shutdown
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
0
2
6
4
8
10
INPUT VOLTAGE (V)
12
14
SHUTDOWN = 0V
T
A
= 25°C
CURRENT INTO PIN 6 ONLY
500
450
400
350
300
250
200
150
100
50
0
DC Supply Current
ACTIVE MODE
I
PGM
= 0V
I
PGM
= V
IN
SLEEP MODE
T
A
= 25°C
0
2
8
4
10
6
INPUT VOLTAGE (V)
12
14
1174 G11
1174 G12
Switch Resistance vs
Input Voltage
50
T
A
= 25°C
Off-Time vs Output Voltage
40
1.3
1.2
1.1
1.0
0.9
0.8
0.7
4
6
8
10 12 14 16
INPUT VOLTAGE (V)
18
20
LTC1174
LTC1174HV
30
20
LTC1174-5
LTC1174HV-5
10
LTC1174-3.3
LTC1174HV-3.3
0
1
3
4
2
OUTPUT VOLTAGE (V)
5
1174 G15
0
1174 G14
U
U
U
5
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