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LTC1779ES6#TRMPBF

P1-P3P4-P6P7-P9P10-P12P13-P14
LTC1779
1
1779fa
For more information www.linear.com/LTC1779
Typical applicaTion
FeaTures DescripTion
250mA Current Mode
Step-Down DC/DC Converter
in ThinSOT
The LTC
®
1779 is a constant frequency current mode step-
down DC/DC converter in a 6-lead ThinSOT package. The
part operates with a 2.5V to 9.8V input and can provide
up to 250mA of output current. Current mode control
provides excellent AC and DC load and line regulation.
The device incorporates an accurate undervoltage lockout
feature that shuts down the LTC1779 when the input volt
-
age falls below 2V.
The LTC1779
boasts a ±2.5% output voltage accuracy
and consumes only 135µA of quiescent current. For ap
-
plications where efficiency is a prime consideration, the
LTC1779 is configured for Burst Mode operation, which
enhances efficiency at low output current.
To further maximize the life of a battery source, the
internal P-channel MOSFET is turned on continuously in
dropout (100% duty cycle
). In shutdown, the device draws
a mere 8µA. High constant operating frequency of 550kHz
allows the use of a small external inductor.
The LTC1779 is available in a low profile (1mm) ThinSOT
package.
applicaTions
n
High Efficiency: Up to 94%
n
250mA Output Current
n
Wide V
IN
Range: 2.5V to 9.8V
n
550kHz Constant Frequency Operation
n
Burst Mode™ Operation at Light Load
n
Low Dropout: 100% Duty Cycle
n
0.8V Reference Allows Low Output Voltages
n
±2.5% Reference Accuracy
n
Current Mode Operation for Excellent Line and Load
Transient Response
n
Low Quiescent Current: 135µA
n
Shutdown Mode Draws Only 8µA Supply Current
n
Low Profile (1mm) ThinSOT™ Package
n
1- or 2-Cell Lithium-Ion-Powered Applications
n
Cellular Telephones
n
Wireless Modems
n
Portable Computers
n
Distributed 3.3V, 2.5V or 1.8V Power Systems
n
Scanners
L, LT , LT C , LT M, Burst Mode, Linear Technology and the Linear logo are registered trademarks
and ThinSOT is a trademark of Linear Technology Corporation. All other trademarks are the
property of their respective owners.
I
TH
/RUN
LTC1779
20k
169k
78.7k
R1
10Ω
L1
22µH
D1
100pF
GND
V
FB
6
5
4
1779 F01a
1
2
3
SW
V
IN
SENSE
–
C1
10µF
16V
C3
0.1µF
C1: TAIYO YUDEN CERAMIC EMK325BJ106MNT
C2: SANYO POSCAP 6TPA47M
D1: IR10BQ015
L1: COILTRONICS UP1B220
V
IN
2.5V
TO 9.8V
V
OUT
2.5V
100mA
C2
47µF
6V
+
LOAD CURRENT (mA)
50
EFFICIENCY (%)
70
90
100
0.1 10 100 1000
1779 F01b
30
1
80
60
40
V
IN
= 3.3V
V
IN
= 6V
V
IN
= 9.8V
V
OUT
= 2.5V
R
SENSE
= 10Ω
Figure 1. LTC1779 High Efficiency 2.5V/100mA Step-Down Converter
Efficiency vs Load Current
LTC1779
2
1779fa
For more information www.linear.com/LTC1779
pin conFiguraTionabsoluTe MaxiMuM raTings
(Note 1)
Input Supply Voltage (V
IN
) ......................... –0.3V to 10V
SENSE
–
, SW Voltages ................... –0.3V to (V
IN
+ 0.3V)
V
FB
, I
TH
/RUN Voltages .............................. –0.3V to 2.4V
SW Peak Output Current (< 10µs) ........................... 0.5A
Storage Ambient Temperature Range ....– 65°C to 150°C
Operating Temperature Range (Note 2)....–40°C to 85°C
Junction Temperature (Note 3) ............................ 150°C
Lead Temperature (Soldering, 10 sec) ................... 300°C
I
TH
/RUN 1
GND 2
V
FB
3
6 SW
5 V
IN
4 SENSE
–
TOP VIEW
S6 PACKAGE
6-LEAD PLASTIC SOT-23
T
JMAX
= 150°C, θ
JA
= 230°C/W
orDer inForMaTion
LEAD FREE FINISH TAPE AND REEL PART MARKING PACKAGE DESCRIPTION TEMPERATURE RANGE
LTC1779ES6#PBF LTC1779ES6#TRPBF LTLP 6-Lead Plastic SOT-23 –40°C to 85°C
Consult LTC Marketing for parts specified with wider operating temperature ranges.
Consult LTC Marketing for information on nonstandard lead based finish parts.
For more information on lead free part marking, go to:
http://www.linear.com/leadfree/
For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/
LTC1779
3
1779fa
For more information www.linear.com/LTC1779
elecTrical characTerisTics
PARAMETER CONDITIONS MIN TYP MAX UNITS
Input DC Supply Current
Normal Operation
Shutdown
UVLO
Typicals at V
IN
= 4.2V (Note 4)
2.5V ≤ V
IN
≤ 9.8V
2.5V ≤ V
IN
≤ 9.8V, V
ITH
/RUN = 0V
V
IN
< UVLO Threshold
135
8
1
240
22
13
µA
µA
µA
Undervoltage Lockout Threshold V
IN
Falling
V
IN
Rising
l
1.60 2.0
2.1
2.5
V
V
Shutdown Threshold (at I
TH
/RUN)
l
0.15 0.325 0.5 V
Start-Up Current Source V
ITH
/RUN = 0V 0.25 0.5 0.85 µA
Regulated Feedback Voltage (Note 5) 0°C to 70°C
(Note 5) –40°C to 85°C
l
l
0.780
0.770
0.800
0.800
0.820
0.830
V
V
Output Voltage Line Regulation 2.5V ≤ V
IN
≤ 9.8V (Note 5) –3 0 3 mV/V
Output Voltage Load Regulation I
TH
/RUN Sinking 5µA (Note 5)
I
TH
/RUN Sourcing 5µA (Note 5)
2.5
2.5
mV/µA
mV/µA
V
FB
Input Current (Note 5) 5 25 nA
Overvoltage Protect Threshold Measured at V
FB
0.820 0.860 0.895 V
Overvoltage Protect Hysteresis 30 mV
Overtemperature Protect Threshold 170 °C
Overtemperature Protect Hysteresis 15 °C
Oscillator Frequency V
FB
= 0.8V
V
FB
= 0V
500 550
100
650 kHz
kHz
R
DS(ON)
of Internal P-Channel FET V
IN
= 4.2V, I
SW
= 100mA 0.85 1.4 Ω
Peak Current Sense Voltage (Note 6) 120 mV
The l denotes specifications that apply over the full operating temperature
range, otherwise specifications are at T
A
= 25°C. V
IN
= 4.2V unless otherwise specified. (Note 2)
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2: The LTC1779E 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.
Note 3: T
J
is calculated from the ambient temperature T
A
and power
dissipation P
D
according to the following formula:
T
J
= T
A
+ (P
D
• θ
J
°C/W)
Note 4: Dynamic supply current is higher due to the gate charge being
delivered at the switching frequency.
Note 5: The LTC1779 is tested in a feedback loop that servos V
FB
to the
output of the error amplifier.
Note 6:
Peak current sense voltage is reduced dependent upon duty cycle
to a percentage of value as given in Figure 2.
P1-P3P4-P6P7-P9P10-P12P13-P14

LTC1779ES6#TRMPBF

Mfr. #:
Buy LTC1779ES6#TRMPBF
Manufacturer:
Analog Devices / Linear Technology
Description:
Switching Voltage Regulators 500mA, 500kHz Step-Down Switching Regulator
Lifecycle:
New from this manufacturer.
Delivery:
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