1
LTC1707
High Efficiency Monolithic
Synchronous Step-Down
Switching Regulator
Figure 1b. Efficiency vs Output Load Current
22µF
16V
47pF
V
IN
*
3V TO
8.5V
1707 F01a
6
2
7
1
5
8
3
SW
V
REF
V
FB
V
IN
RUN
SYNC/MODE
I
TH
LTC1707
+
15µH
100µF
6.3V
80.6k
*V
OUT
FOLLOWS V
IN
FOR
3V < VIN < 3.3V
249k
V
OUT
3.3V
+
GND
4
OUTPUT CURRENT (mA)
1
70
EFFICIENCY (%)
90
95
100
10 100 1000
1707 F01b
85
80
75
V
OUT
= 3.3V
V
IN
= 6V
V
IN
= 3.6V
V
IN
= 8.4V
Figure 1a. High Efficiency Low Dropout Step-Down Converter
The LTC
®
1707 is a high efficiency monolithic current
mode synchronous buck regulator using a fixed frequency
architecture. The operating supply range is from 8.5V
down to 2.85V, making it suitable for both single and dual
lithium-ion battery-powered applications. Burst Mode op-
eration provides high efficiency at low load currents.
100% duty cycle provides low dropout operation, extend-
ing operating time in battery-powered systems.
The switching frequency is internally set at 350kHz,
allowing the use of small surface mount inductors. For
noise sensitive applications it can be externally synchro-
nized up to 550kHz. Burst Mode operation is inhibited
during synchronization or when the SYNC/MODE pin is
pulled low preventing low frequency ripple from interfer-
ing with audio circuitry. Soft-start is provided by an
external capacitor.
The internal synchronous MOSFET switch increases effi-
ciency and eliminates the need for an external Schottky
diode, saving components and board space. Low output
voltages down to 0.8V are easily achieved due to the 0.8V
internal reference. The LTC1707 comes in an 8-lead SO
package.
600mA Output Current (V
IN
4V)
High Efficiency: Up to 96%
Constant Frequency: 350kHz Synchronizable
to 550kHz
2.85V to 8.5V V
IN
Range
0.8V Feedback Reference Allows Low Voltage
Outputs: 0.8V V
OUT
V
IN
No Schottky Diode Required
1.19V ±1% Reference Output Pin
Selectable Burst Mode
TM
Operation/Pulse
Skipping Mode
Low Dropout Operation: 100% Duty Cycle
Precision 2.7V Undervoltage Lockout
Current Mode Control for Excellent Line and
Load Transient Response
Low Quiescent Current: 200µA
Shutdown Mode Draws Only 11µA Supply Current
Available in 8-Lead SO Package
, LTC and LT are registered trademarks of Linear Technology Corporation.
Burst Mode is a trademark of Linear Technology Corporation.
Cellular Telephones
Portable Instruments
Wireless Modems
RF Communications
Distributed Power Systems
Single and Dual Cell Lithium
FEATURES
DESCRIPTIO
U
APPLICATIO S
U
TYPICAL APPLICATIO
U
2
LTC1707
ORDER PART
NUMBER
S8 PART MARKING
Consult factory for Military grade parts.
1707
1707I
LTC1707CS8
LTC1707IS8
T
JMAX
= 125°C, θ
JA
= 120°C/ W
TOP VIEW
V
REF
SYNC/MODE
V
IN
SW
I
TH
RUN/SS
V
FB
GND
S8 PACKAGE
8-LEAD PLASTIC SO
1
2
3
4
8
7
6
5
(Note 1)
Input Supply Voltage ................................0.3V to 10V
I
TH
Voltage ................................................. 0.3V to 5V
RUN/SS, V
FB
Voltages ...............................0.3V to V
IN
SYNC/MODE Voltage .................................0.3V to V
IN
P-Channel Switch Source Current (DC) .............. 800mA
N-Channel Switch Sink Current (DC) .................. 800mA
Peak SW Sink and Source Current ......................... 1.5A
Operating Ambient Temperature Range
Commercial ............................................ 0°C to 70°C
Industrial ........................................... –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
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
I
VFB
Feedback Current (Note 3) 6 60 nA
V
FB
Regulated Feedback Voltage (Note 3) 0.78 0.80 0.82 V
V
OVL
Output Overvoltage Lockout V
OVL
= V
OVL
– V
FB
20 60 110 mV
V
FB
Reference Voltage Line Regulation V
IN
= 3V to 8.5V (Note 3) 0.002 0.01 %/V
V
LOADREG
Output Voltage Load Regulation I
TH
Sinking 2µA (Note 3) 0.5 0.8 %
I
TH
Sourcing 2µA (Note 3) 0.5 0.8 %
I
S
Input DC Bias Current (Note 4)
Pulse Skipping Mode V
IN
= 8.5V, V
OUT
= 3.3V, V
SYNC/MODE
= 0V 300 µA
Burst Mode Operation V
ITH
= 0V, V
IN
= 8.5V, V
SYNC/MODE
= Open 200 320 µA
Shutdown V
RUN/SS
= 0V, 3V < V
IN
< 8.5V 11 35 µA
Shutdown V
RUN/SS
= 0V, V
IN
< 3V 6 µA
V
RUN/SS
Run/SS Threshold V
RUN/SS
Ramping Positive 0.4 0.7 1.0 V
I
RUN/SS
Soft-Start Current Source V
RUN/SS
= 0V 1.2 2.25 3.3 µA
I
SYNC/MODE
SYNC/MODE Pull-Up Current V
SYNC/MODE
= 0V 0.5 1.5 2.5 µA
f
OSC
Oscillator Frequency V
FB
= 0.7V 315 350 385 kHz
V
FB
= 0V 35 kHz
V
UVLO
Undervoltage Lockout V
IN
Ramping Down from 3V (0°C to 70°C) 2.55 2.70 2.85 V
V
IN
Ramping Up from 0V (0°C to 70°C) 2.60 2.80 3.00 V
V
IN
Ramping Down from 3V (–40°C to 85°C) 2.45 2.70 2.85 V
V
IN
Ramping Up from 0V (–40°C to 85°C) 2.50 2.80 3.00 V
R
PFET
R
DS(ON)
of P-Channel FET I
SW
= –100mA 0.5 0.7
R
NFET
R
DS(ON)
of N-Channel FET I
SW
= –100mA 0.6 0.8
I
PK
Peak Inductor Current V
IN
= 4V, I
TH
= 1.4V, Duty Cycle < 40% 0.70 0.915 1.10 A
I
LSW
SW Leakage V
RUN/SS
= 0V ±10 ±1000 nA
V
REF
Reference Output Voltage I
REF
= 0µA 1.178 1.19 1.202 mV
V
REF
Reference Output Load Regulation 0V I
REF
100µA 2.3 15 mV
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 formula:
T
J
= T
A
+ (P
D
• 110°C/W)
Note 3: The LTC1707 is tested in a feedback loop that servos V
FB
to the
balance point for the error amplifier (V
ITH
= 0.8V).
Note 4: Dynamic supply current is higher due to the gate charge being
delivered at the switching frequency.
The denotes specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 5V unless otherwise specified.
ABSOLUTE AXI U RATI GS
WWWU
PACKAGE/ORDER I FOR ATIO
UU
W
ELECTRICAL CHARACTERISTICS
3
LTC1707
Efficiency vs Input Voltage
INPUT VOLTAGE (V)
0
EFFICIENCY (%)
90
95
100
8
1707 G01
85
80
75
2
4
6
10
V
OUT
= 2.5V
L = 15µH
Burst Mode OPERATION
I
LOAD
= 100mA
I
LOAD
= 300mA
I
LOAD
= 10mA
OUTPUT CURRENT (mA)
1
70
65
60
55
50
EFFICIENCY (%)
90
95
100
10 100 1000
1707 G02
85
80
75
Burst Mode
OPERATION
PULSE SKIPPING
MODE
V
IN
= 3.6V
V
OUT
= 2.5V
L = 15µH
OUTPUT CURRENT (mA)
1
70
EFFICIENCY (%)
90
95
100
10 100 1000
1707 G03
85
80
75
V
OUT
= 2.5V
L = 15µH
Burst Mode OPERATION
V
IN
= 2.8V
V
IN
= 3.6V
V
IN
= 7.2V
Efficiency vs Load Current
Efficiency vs Load Current
Undervoltage Lockout Threshold
vs Temperature
TEMPERATURE (°C)
–50 –25
2.50
2.55
UNDERVOLTAGE LOCKOUT THRESHOLD (V)
2.60
2.70
2.75
2.80
75 100
3.00
1707 G04
2.65
0 25 50 125
2.85
2.90
2.95
V
IN
RAMPING UP
V
IN
RAMPING DOWN
DC Supply Current
vs Input Voltage
INPUT VOLTAGE (V)
2.5
DC SUPPLY CURRENT (µA)
50
100
150
6.5
350
1707 G05
0
4.5
3.5
7.5
5.5 8.5
200
250
300
T
J
= 25°C
V
OUT
= 1.8V
LOAD CURRENT = 0A
Burst Mode
OPERATION
PULSE SKIPPING
MODE
Supply Current in Shutdown
vs Input Voltage
INPUT VOLTAGE (V)
2.5
4
SUPPLY CURRENT IN SHUTDOWN (µA)
6
10
12
14
6.5
22
1707 G06
8
4.5
3.5
7.5
5.5 8.5
16
18
20
V
RUN/SS
= 0V
T
J
= 85°C
T
J
= 25°C
T
J
= –40°C
Reference Voltage
vs Temperature
Oscillator Frequency
vs Temperature
TEMPERATURE (°C)
–50 –25
1.180
REFERENCE VOLTAGE (V)
1.185
1.190
75 100
1.200
1707 G07
0 25 50 125
1.195
V
IN
= 5V
Oscillator Frequency
vs Input Voltage
TEMPERATURE (°C)
–50 –25
300
OSCILLATOR FREQUENCY (kHz)
310
330
340
350
75 100
390
1707 G08
320
0 25 50 125
360
370
380
V
IN
= 5V
INPUT VOLTAGE (V)
2.5
300
OSCILLATOR FREQUENCY (kHz)
310
330
340
350
6.5
390
1627 G09
320
4.5
3.5
7.5
5.5 8.5
360
370
380
TYPICAL PERFOR A CE CHARACTERISTICS
UW

LTC1707IS8#TRPBF

Mfr. #:
Manufacturer:
Analog Devices / Linear Technology
Description:
Switching Voltage Regulators Hi Eff Mono Sync Buck Sw Reg
Lifecycle:
New from this manufacturer.
Delivery:
DHL FedEx Ups TNT EMS
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