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LTC3448EDD#TRPBF

P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P20
1
LTC34 48
3448f
■
High Efficiency: Up to 96%
■
Very Low Quiescent Supply Current: 32
µ
A During
Linear Regulator Operation
■
600mA Output Current (Buck Converter)
■
Optionally Operates as Linear Regulator Below
3mA—External or Automatic ON/OFF
■
2.5V to 5.5V Input Voltage Range
■
1.5MHz or 2.25MHz Constant Frequency Operation
or External Synchronization
■
No Schottky Diode Required
■
Low Dropout Operation: 100% Duty Cycle
■
0.6V Reference Allows Low Output Voltages
■
Shutdown Mode Draws <1µA Supply Current
■
Current Mode Operation for Excellent Line and
Load Transient Response
■
Overtemperature Protected
■
Low Profile (3mm × 3mm) 8-Lead DFN and 8-Lead
MSOP Packages
■
Cellular Telephones
■
Personal Information Appliances
■
Wireless and DSL Modems
■
Digital Still Cameras
■
MP3 Players
■
Portable Instruments
1.5V High Efficiency Regulator with Automatic LDO Mode
1.5MHz/2.25MHz, 600mA
Synchronous Step-Down
Regulator with LDO Mode
Efficiency and Power Loss vs Load Current
FEATURES
DESCRIPTIO
U
APPLICATIO S
U
TYPICAL APPLICATIO
U
The LTC
®
3448 is a high efficiency, monolithic, synchronous
buck regulator using a constant frequency, current mode
architecture. Supply current during operation is only 32µA
(linear regulator mode) and drops to <1µA in shutdown. The
2.5V to 5.5V input voltage range makes the LTC3448 ide-
ally suited for single Li-Ion battery-powered applications.
100% duty cycle provides low dropout operation, extend-
ing battery life in portable systems. At moderate output load
levels, PWM pulse skipping mode operation provides very
low output ripple voltage for noise sensitive applications.
The LTC3448 automatically switches into linear regulator
operation at very low load currents to maintain <5mV
P-P
output voltage ripple. Supply current in this mode is
typically 32µA. The switch to linear regulator mode occurs
at a threshold of 3mA. Linear regulator operation can be set
to on, off or automatic turn on/off.
Switching frequency is selectable at either 1.5MHz or
2.25MHz, allowing the use of small surface mount induc-
tors and capacitors.
The internal synchronous switch increases efficiency and
eliminates the need for an external Schottky diode. Low
output voltages are easily supported with the 0.6V feed-
back reference voltage. The LTC3448 is available in a low
profile 3mm × 3mm DFN package or thermally enhanced
8-lead MSOP.
V
IN
474k
22pF
316k
C
IN
4.7µF
V
IN
2.5V TO 5.5V
LTC3448
FREQ
SYNC
2.2µH
3448 TA01a
SW
RUN
V
OUT
MODE
V
FB
GND
C
OUT
4.7µF
V
OUT
1.5V
, LTC and LT are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
Protected by U.S. Patents including 5481178, 6580258, 6304066, 6127815,
6498466, 6611131. Others pending.
LOAD CURRENT (A)
30
EFFICIENCY (%)
POWER LOSS (W)
90
100
20
10
80
50
70
60
40
0.0001 0.01 0.1 1
23448 TA01b
0
1
0.1
0.01
0.001
0.0001
0.001
V
IN
= 3.6V
V
OUT
= 1.5V
T
A
= 25°C
POWER LOSS
EFFICIENCY
2
LTC34 48
3448f
LTC3448EDD
T
JMAX
= 125°C, θ
JA
= 43°C/ W
EXPOSED PAD (PIN 9) IS GND
MUST BE SOLDERED TO PCB
ORDER PART
NUMBER
Input Supply Voltage .................................. – 0.3V to 6V
RUN, SYNC Voltages ................... – 0.3V to (V
IN
+ 0.3V)
MODE Voltage ............................. – 0.3V to (V
IN
+ 0.3V)
FREQ, V
FB
Voltages...................... –0.3V to (V
IN
+ 0.3V)
SW Voltage .................................. – 0.3V to (V
IN
+ 0.3V)
V
OUT
Voltage................................ – 0.3V to (V
IN
+ 0.3V)
P-Channel Switch Source Current (DC) ............. 800mA
N-Channel Switch Sink Current (DC) ................. 800mA
DD PART MARKING
Consult LTC Marketing for parts specified with wider operating temperature ranges.
LBMJ
ABSOLUTE AXI U RATI GS
WWWU
PACKAGE/ORDER I FOR ATIO
UU
W
(Note 1)
V
OUT
(LDO) Source Current .................................. 25mA
Peak SW Sink and Source Current ........................ 1.3A
Operating Temperature Range (Note 2) .. – 40°C to 85°C
Junction Temperature (Notes 3, 7) ...................... 125°C
Storage Temperature Range ................ – 65°C to 125°C
Lead Temperature (Soldering, 10 sec)
MSOP Only ...................................................... 300°C
TOP VIEW
9
DD PACKAGE
8-LEAD (3mm × 3mm) PLASTIC DFN
5
6
7
8
4
3
2
1V
FB
V
OUT
MODE
V
IN
RUN
SYNC
FREQ
SW
LTC3448EMS8E
ORDER PART
NUMBER
MS8 PART MARKING
LTBMK
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
I
VFB
Feedback Current ● ±30 nA
V
FB
Regulated Feedback Voltage T
A
= 25°C 0.5880 0.6 0.6120 V
(Note 4) 0°C ≤ T
A
≤ 85°C 0.5865 0.6 0.6135 V
–40°C ≤ T
A
≤ 85°C ● 0.5850 0.6 0.6150 V
∆V
FB
Reference Voltage Line Regulation V
IN
= 2.5V to 5.5V (Note 4) ● 0.2 0.4 %/V
∆V
OVL
Output Overvoltage Lockout ∆V
OVL
= V
OVL
– V
FB
15 35 55 mV
∆V
OVL
= (V
OVL
– V
OUT
) • 100/V
OUT
2.5 5.8 9.2 %
∆V
OUT
Output Voltage Line Regulation V
IN
= 2.5V to 5.5V (LDO) 0.1 0.8 %/V
I
PK
Peak Inductor Current V
FB
= 0.5V or V
OUT
= 90%, 0.7 1 1.3 A
Duty Cycle < 35%
V
LOADREG
Output Voltage Load Regulation LDO, 1mA to 10mA 0.5 %/V
V
OUT(MAX)
Maximum Output Voltage (Note 9) V
IN
– 0.7 V
IN
– 0.3 V
V
IN
Input Voltage Range ● 2.5 5.5 V
The ● denotes specifications which apply over the full operating
temperature range, otherwise specifications are T
A
= 25°C. V
IN
= 3.6V unless otherwise specified.
ELECTRICAL CHARACTERISTICS
1
2
3
4
V
FB
V
OUT
MODE
V
IN
8
7
6
5
RUN
SYNC
FREQ
SW
TOP VIEW
9
MS8E PACKAGE
8-LEAD PLASTIC MSOP
T
JMAX
= 125°C, θ
JA
= 40°C/ W
EXPOSED PAD (PIN 9) IS GND
MUST BE SOLDERED TO PCB
3
LTC34 48
3448f
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
I
S
Input DC Bias Current V
IN
= 3.6V (Note 5)
Active Mode (Pulse Skip, No LRO) V
FB
= 0.5V or V
OUT
= 90%, I
LOAD
= 0A, 1.5MHz 250 375 µA
V
FB
= 0.5V or V
OUT
= 90%, I
LOAD
= 0A, 2.25MHz 275 400 µA
Linear Regulator Operation (LRO) I
LOAD
≤ I
LDO(ON)
32 43 µA
Shutdown V
RUN
= 0V, V
IN
= 5.5V 0.1 1 µA
f
OSC
Oscillator Frequency FREQ = Low, V
IN
= 3.6V ● 1.2 1.5 1.8 MHz
FREQ = High
● 1.8 2.25 2.7 MHz
f
SYNC
Synchronization Frequency (Note 6) 1.5 >4 MHz
V
TH(SYNC)
SYNC Activation Input Threshold 1 1.3 V
R
PFET
R
DS(ON)
of P-Channel FET I
SW
= 100mA 0.4 Ω
R
NFET
R
DS(ON)
of N-Channel FET I
SW
= –150mA 0.35 Ω
I
LSW
SW Leakage V
RUN
= 0V, V
SW
= 0V or 5V, V
IN
= 5V ±0.01 ±1 µA
V
RUNH
RUN Threshold High ● 1.5 V
V
RUNL
RUN Threshold Low ● 0.3 V
I
RUN
RUN Leakage Current ● ±0.01 ±1 µA
V
FREQH
FREQ Threshold High ● V
IN
– 1 V
V
FREQL
FREQ Threshold Low ● 1V
I
FREQ
FREQ Leakage Current ● ±0.01 ±1 µA
V
MODEH
MODE Threshold High ● V
IN
– 0.15 V
V
MODEL
MODE Threshold Low ● 0.12 V
I
MODE
MODE Leakage Current ● ±0.1 ±1 µA
I
SYNC
SYNC Leakage Current ● ±0.01 ±1 µA
I
LDO(ON)
LRO ON Load Current Threshold 2.2mH Inductor (Note 8) 3 5 mA
I
LDO(OFF)
LRO OFF Load Current Threhold 8 11 17 mA
The ● denotes specifications which apply over the full operating
temperature range, otherwise specifications are T
A
= 25°C. V
IN
= 3.6V unless otherwise specified.
ELECTRICAL CHARACTERISTICS
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2: The LTC3448E 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
)(43°C/W)
Note 4: The LTC3448 is tested in a proprietary test mode that connects
V
FB
to the output of the error amplifier.
Note 5: Dynamic supply current is higher due to the gate charge being
delivered at the switching frequency. LRO is “linear regulator operation.”
Note 6: 4MHz operation is guaranteed by design but is not production
tested and is subject to duty cycle limitations.
Note 7: This IC includes overtemperature protection that is intended to
protect the device during momentary overload conditions. Junction
temperature will exceed 125°C when overtemperature is active. Continu-
ous operation above the specified maximum operating junction tempera-
ture may impair device reliability.
Note 8: The load current below which the switching regulator turns off and
the LDO turns on is, to first order, inversely proportional to the value of
the inductor. This effect is covered in more detail in the Operation section.
This parameter is not production tested but is guaranteed by design.
Note 9: For 2.5V < V
IN
< 2.7V the output voltage is limited to V
IN
– 0.7V
to ensure regulation in linear regulator mode. This parameter is not
production tested but is guaranteed by design.
P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P20

LTC3448EDD#TRPBF

Mfr. #:
Buy LTC3448EDD#TRPBF
Manufacturer:
Analog Devices / Linear Technology
Description:
Switching Voltage Regulators 600mA, Synch Step-Down Reg in DFN
Lifecycle:
New from this manufacturer.
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