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LTC1771IS8#PBF

P1-P3P4-P6P7-P9P10-P12P13-P15P16-P16
1
LTC1771
■
Very Low Standby Current: 10µA
■
Available in Space-Saving 8-Lead MSOP Package
■
Output Currents: Up to 5A
■
Wide V
IN
Range: 2.8V to 20V Operation
■
V
OUT
Range: 1.23V to 18V
■
High Efficiency: Over 93% Possible
■
±2% Output Accuracy
■
Very Low Dropout Operation: 100% Duty Cycle
■
Current Mode Operation for Excellent Line and
Load Transient Response
■
Defeatable Burst Mode
TM
Operation
■
Short-Circuit Protected
■
Optional Programmable Soft-Start
■
Micropower Shutdown: I
Q
= 2µA
The LTC
®
1771 is a high efficiency current mode step-
down DC/DC controller that draws as little as 10µA DC
supply current to regulate the output at no load while
maintaining high efficiency for loads up to several amps.
The LTC1771 drives an external P-channel power MOSFET
using a current mode, constant off-time architecture. An
external sense resistor is used to program the operating
current level. Current mode control provides short-circuit
protection, excellent transient response and controlled
start-up behavior. Burst Mode operation enables the
LTC1771 to maintain high efficiency down to extremely
low currents. Shutdown mode further reduces the supply
current to a mere 2µA. For low noise applications, Burst
Mode operation can be easily disabled with the MODE pin.
Wide input supply range of 2.8V to 18V (20V maximum)
and 100% duty cycle operation for low dropout make the
LTC1771 ideal for a wide variety of battery-powered appli-
cations where maximizing battery life is important.
The LTC1771’s availability in both 8-lead MSOP and SO
packages provides for a minimum area solution.
■
Cellular Telephones and Wireless Modems
■
1- to 4-Cell Lithium-Ion-Powered Applications
■
Portable Instruments
■
Battery-Powered Equipment
■
Battery Chargers
■
Scanners
Figure 1. High Efficiency Step-Down Converter
10µA Quiescent Current
High Efficiency Step-Down
DC/DC Controller
, LTC and LT are registered trademarks of Linear Technology Corporation.
Burst Mode is a trademark of Linear Technology Corporation.
RUN/SS
I
TH
V
FB
V
IN
V
IN
V
IN
4.5V TO 18V
R
C
10k
R
SENSE
0.05Ω
R2
1.64M
1%
R1
1M
1%
M1
Si6447DQ
UPS5817
L1
15µH
C
C
22OpF
C
FF
5pF
22µF
25V
C
OUT
150µF
6.3V
V
OUT
3.3V
2A
1771 F01
C
SS
0.01µF
PGATE
MODE
LTC1771
GND
SENSE
+
+
LTC1771 Efficiency
LOAD CURRENT (mA)
EFFICIENCY (%)
100
90
80
70
60
50
40
0.1 1 100 1000 10000
1771 F01b
10
V
IN
= 5V
V
IN
= 10V
V
IN
= 15V
V
OUT
= 3.3V
R
SENSE
= 0.05Ω
FEATURES
DESCRIPTIO
U
APPLICATIO S
U
TYPICAL APPLICATIO
U
2
LTC1771
The ● denotes specifications which apply over the full operating temperature range, otherwise specifications are T
A
= 25°C.
V
IN
= 10V, V
RUN
= open unless otherwise specified.
LTC1771EMS8
T
JMAX
= 125°C, θ
JA
= 200°C/W
ORDER PART
NUMBER
Input Supply Voltage (V
IN
)........................ –0.3V to 20V
Peak Driver Output Current < 10µs (PGATE) ............. 1A
RUN/SS Voltage ......................... –0.3V to (V
IN
+ 0.3V)*
MODE Voltage .......................................... –0.3V to 20V
I
TH
, V
FB
Voltage .......................................... –0.3V to 5V
SENSE Voltage (V
IN
> 12V)..(V
IN
– 12V) to (V
IN
+ 0.3V)*
SENSE Voltage (V
IN
≤ 12V) ........ –0.3V to (V
IN
+ 0.3V)*
(Note 1)
Consult factory for Military grade parts.
Junction Temperature (Note 2)............................ 125°C
Operating Temperature Range (Note 3)
LTC1771E......................................... –40°C to 85°C
LTC1771I ......................................... –40°C to 85°C
Storage Temperature Range ................. –65°C to 150°C
Lead Temperature (Soldering, 10 sec)..................300°C
LTC1771ES8
LTC1771IS8
ORDER PART
NUMBER
RUN/SS
I
TH
V
FB
GND
1
2
3
4
8
7
6
5
MODE
SENSE
V
IN
PGATE
TOP VIEW
MS8 PACKAGE
8-LEAD PLASTIC MSOP
MS8 PART MARKING
TOP VIEW
MODE
SENSE
V
IN
PGATE
RUN/SS
I
TH
V
FB
GND
S8 PACKAGE
8-LEAD PLASTIC SO
1
2
3
4
8
7
6
5
T
JMAX
= 125°C, θ
JA
= 110°C/W
S8 PART MARKING
1771
1771I
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
V
FB
Feedback Voltage (Note 5) ● 1.205 1.230 1.255 V
I
FB
Feedback Current (Note 5) ● 110 nA
I
SUPPLY
No-Load Supply Current V
IN
= 10V, I
LOAD
= 0 (Note 6) 10 µA
∆V
LINEREG
Reference Voltage Line Regulation V
IN
= 5V to 15V (Note 5) ● 0.003 0.03 %/V
∆V
LOADREG
Output Voltage Load Regulation I
TH
= 0.5V to 2V, Burst Disabled (Note 5) ● 0.25 1 %
I
Q
Input DC Supply Current (Note 4)
Active Mode (PGATE = 0V) V
IN
= 2.8V to 18V 150 235 µA
Sleep Mode (Note 6) V
IN
= 2.8V to 18V, V
FB
= 1.5V 9 15 µA
Shutdown V
IN
= 2.8V to 18V, V
RUN
= 0V 2 6 µA
Short Circuit V
IN
= 2.8V to 18V, V
FB
= 0V 175 275 µA
∆V
SENSE(MAX)
Maximum Current Sense Threshold V
FB
= V
REF
– 20mV ● 110 140 180 mV
∆V
SENSE(MIN)
Minimum Current Sense Threshold V
FB
= V
REF
+ 20mV, Burst Disabled –25 mV
∆V
SENSE(SLEEP)
Sleep Current Sense Threshold I
TH
= 1V 50 mV
t
OFF
Switch Off Time V
FB
at Regulated Value 3 3.5 4 µs
V
FB
= 0V 70 µs
V
MODE
Mode Pin Threshold V
MODE
Rising ● 0.5 1.3 2 V
LTKD
ABSOLUTE AXI U RATI GS
WWWU
PACKAGE/ORDER I FOR ATIO
UU
W
ELECTRICAL CHARACTERISTICS
*RUN/SS and SENSE cannot exceed 20V.
3
LTC1771
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:
LTC1771S8: T
J
= T
A
+ (P
D
)(110°C/W)
LTC1771MS8: T
J
= T
A
+ (P
D
)(150°C/W)
Note 3: The LTC1771E is guaranteed to meet performance specifications
from 0°C to 70°C. Specifications over the –40°C to 85°C operating
temperature range are assured by design, characterization and correlation
with statistical process controls. The LTC1771I is guaranteed and tested
over the –40°C to 85°C operating temperature range.
The ● denotes specifications which apply over the full operating temperature range, otherwise specifications are T
A
= 25°C.
V
IN
= 10V, V
RUN
= open unless otherwise specified.
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
V
RUN/SS
RUN/SS Pin Threshold V
RUN/SS
Rising ● 0.5 1.0 2 V
I
RUN
Source Current V
RUN
= 0V, V
IN
= 2.8V to 18V 0.3 1 3 µA
PGATE t
r
, t
f
PGATE Transition Time (Note 7)
Rise Time C
LOAD
= 2000pF 70 140 ns
Fall Time C
LOAD
= 2000pF 70 140 ns
Note 4: Dynamic supply current is higher due to the gate charge being
delivered at the switching frequency. See Applications Information.
Note 5: The LTC1771 is tested in a feedback loop that servos V
FB
to the
balance point for the error amplifier (V
ITH
= 1.23V).
Note 6: No-load supply current consists of sleep mode current (9µA
typical) plus a small switching component necessary to overcome
Schottky diode leakage and feedback resistor current.
Note 7: t
r
and t
f
are measured at 10% to 90% levels.
ELECTRICAL CHARACTERISTICS
TYPICAL PERFOR A CE CHARACTERISTICS
UW
Efficiency vs Input Voltage
INPUT VOLTAGE (V)
2
60
EFFICIENCY (%)
70
80
90
100
46810
1771 G01
12 14 16 18 20
I
LOAD
= 50mA
I
LOAD
= 1mA
FIGURE 1 CIRCUIT
I
LOAD
= 1A
LOAD CURRENT (mA)
0.1
40
EFFICIENCY (%)
50
60
70
80
1 10 1000100
1771 G02
30
20
10
0
90
100
Burst Mode OPERATION
ENABLED
Burst Mode OPERATION
DISABLED
V
IN
= 10V
FIGURE 1 CIRCUIT
INPUT VOLTAGE (V)
0
∆V
OUT
(%)
0
0.1
0.2
20
1771 G03
–0.1
–0.2
–0.4
5
10
15
–0.3
0.4
0.3
I
LOAD
= 100mA
I
LOAD
= 1A
FIGURE 1 CIRCUIT
Efficiency vs Load Current Line Regulation
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LTC1771IS8#PBF

Mfr. #:
Buy LTC1771IS8#PBF
Manufacturer:
Analog Devices / Linear Technology
Description:
Switching Voltage Regulators Low Iq Step-dn DC/DC Controller
Lifecycle:
New from this manufacturer.
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