step- down DC/DC converter. Intended for medium power
applications, it operates from a 2.5V to 5.5V input voltage
range and has a user configurable operating frequency
up to 4MHz, allowing the use of tiny, low cost capacitors
and inductors 2mm or less in height. The output voltage
is adjustable from 0.8V to 5V. Internal sychronous 0.11Ω
power switches with 2.4A peak current ratings provide
high efficiency. The LTC3568’s current mode architecture
and external compensation allow the transient response
to be optimized over a wide range of loads and output
capacitors.
The LTC3568 can be configured for automatic power sav-
ing Burst Mode operation to reduce gate charge losses
when the load current drops below the level required for
continuous operation. For reduced noise and RF interfer-
ence, the SYNC/MODE pin can be configured to skip pulses
or provide forced continuous operation.
To further maximize battery life, the P-channel MOSFET
is turned on continuously in dropout (100% duty cycle)
with a low quiescent current of 60µA. In shutdown, the
device draws <1µA.
L,
LT, LTC, LTM, Linear Technology, the Linear logo, OPTI-LOOP and Burst Mode are
registered trademarks and ThinSOT is a trademark of Linear Technology Corporation. All other
trademarks are the property of their respective owners. Protected by U.S. Patents including
5481178, 6580258, 6304066, 6127815, 6611131.
applicaTions
n
n
n
n
n
Notebook Computers
Digital Cameras
Cellular Phones
Handheld Instruments
Board Mounted Power Supplies
Typical applicaTion
V
IN
2.5V TO 5.5V
22µF
V
IN
SYNC/MODE
PGOOD
LTC3568
I
TH
13k
1000pF
324k
NOTE: IN DROPOUT, THE OUTPUT TRACKS
THE INPUT VOLTAGE
SHDN/R
T
SGND
PGND
412k
V
FB
PV
IN
SV
IN
SW
887k
L1
2µH
Efficiency vs Load Current
100
95
EFFICIENCY (%)
90
85
POWER LOSS
80
75
70
V
IN
= 3.3V
V
OUT
= 2.5V
f
O
= 1MHz
Burst Mode
OPERATION
1
10
100
1000
LOAD CURRENT (mA)
10
1000
EFFICIENCY
POWER LOSS (mW)
100
V
OUT
2.5V/1.8A
22µF + 10µF
3568 F01
1
10000
Figure 1. Step-Down 1.8A Regulator
3568 TA01
3568fa
LTC3568
absoluTe MaxiMuM raTings
(Note 1)
pin conFiguraTion
TOP VIEW
SHDN/R
T
SYNC/MODE
SGND
SW
PGND
1
2
3
4
5
11
10 I
TH
9 V
FB
8 PGOOD
7 SV
IN
6 PV
IN
PV
IN
, SV
IN
Voltages ..................................... –0.3V to 6V
V
FB
, I
TH
, SHDN/R
T
Voltages .......... –0.3V to (V
IN
+ 0.3V)
SYNC/MODE Voltage .................... –0.3V to (V
IN
+ 0.3V)
SW Voltage ................................... –0.3V to (V
IN
+ 0.3V)
PGOOD Voltage ............................................ –0.3V to 6V
Operating Junction Temperature Range
(Note 2) ............................................. –40°C to 125°C
Junction Temperature (Notes 5, 8)........................ 125°C
Storage Temperature Range .................. –65°C to 125°C
DD PACKAGE
10-LEAD (3mm 3mm) PLASTIC DFN
T
JMAX
= 125°C,
θ
JA
= 43°C/W,
θ
JC
= 3°C/W
EXPOSED PAD (PIN 11) IS GND, MUST BE SOLDERED TO PCB
orDer inForMaTion
LEAD FREE FINISH
LTC3568EDD#PBF
LTC3568IDD#PBF
LEAD BASED FINISH
LTC3568EDD
LTC3568IDD
TAPE AND REEL
LTC3568EDD#TRPBF
LTC3568IDD#TRPBF
TAPE AND REEL
LTC3568EDD#TR
LTC3568IDD#TR
PART MARKING*
LCSG
LCSG
PART MARKING*
LCSG
LCSG
PACKAGE DESCRIPTION
10-Lead (3mm
×
3mm) Plastic DFN
10-Lead (3mm
×
3mm) Plastic DFN
PACKAGE DESCRIPTION
10-Lead (3mm
×
3mm) Plastic DFN
10-Lead (3mm
×
3mm) Plastic DFN
TEMPERATURE RANGE
–40°C to 125°C
–40°C to 125°C
TEMPERATURE RANGE
–40°C to 125°C
–40°C to 125°C
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
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/
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 3.3V, R
T
= 324k unless otherwise specified. (Note 2)
SYMBOL
V
IN
I
FB
V
FB
ΔV
LINEREG
ΔV
LOADREG
g
m(EA)
I
S
PARAMETER
Operating Voltage Range
Feedback Pin Input Current
Feedback Voltage
Reference Voltage Line Regulation
Output Voltage Load Regulation
Error Amplifier Transconductance
Input DC Supply Current (Note 4)
Active Mode
Sleep Mode
Shutdown
Shutdown Threshold High
Active Oscillator Resistor
(Note 3)
LTC3568E (Note 3)
LTC3568I (Note 3)
V
IN
= 2.25V to 5V
I
TH
= 0.36, (Note 3)
I
TH
= 0.84, (Note 3)
I
TH
Pin Load = ±5µA (Note 3)
V
FB
= 0.75V, SYNC/MODE = 3.3V
V
SYNC/MODE
= 3.3V, V
FB
= 1V
V
SHDN/RT
= 3.3V
l
l
l
l
elecTrical characTerisTics
CONDITIONS
MIN
2.25
0.784
0.780
TYP
MAX
5.5
±0.1
UNITS
V
µA
V
V
%/V
%
%
µS
0.8
0.8
0.04
0.02
–0.02
800
240
62
0.1
V
IN
– 0.6
324k
0.816
0.816
0.2
0.2
–0.2
350
100
1
V
IN
– 0.4
1M
µA
µA
µA
V
Ω
V
SHDN/RT
3568fa
LTC3568
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 3.3V, R
T
= 324k unless otherwise specified. (Note 2)
f
OSC
f
SYNC
I
LIM
R
DS(ON)
I
SW(LKG)
V
UVLO
PGOOD
RPGOOD
Oscillator Frequency
Synchronization Frequency
Peak Switch Current Limit
Top Switch On-Resistance (Note 6)
Bottom Switch On-Resistance (Note 6)
Switch Leakage Current
Undervoltage Lockout Threshold
Power Good Threshold
Power Good Pull-Down On-Resistance
R
T
= 324k
(Note 7)
(Note 7)
I
TH
= 1.3
V
IN
= 3.3V
V
IN
= 3.3V
V
IN
= 6V, V
ITH/RUN
= 0V, V
FB
= 0V
V
IN
Ramping Down
V
FB
Ramping Up, SHDN/R
T
= 1V
V
FB
Ramping Down, SHDN/R
T
= 1V
0.85
0.4
2.4
3
0.11
0.11
0.01
2
6.8
–7.6
118
200
1
1.15
4
4
4
0.15
0.15
1
2.25
MHz
MHz
MHz
A
Ω
Ω
µA
V
%
%
Ω
elecTrical characTerisTics
Note 1:
Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2:
The LTC3568 is tested under pulsed load conditions such that T
J
=
T
A
. The LTC3568E is guaranteed to meet performance specifications from
0°C to 85°C. Specifications over the –40°C to 125°C operating junction
temperature range are assured by design, characterization and correlation
with statistical process controls. The LTC3568I is guaranteed over the
full –40°C to 125°C operating junction temperature range. The maximum
ambient temperature is determined by specific operating conditions in
conjunction with board layout, the rated package thermal resistors and
other environmental factors.
Note 3:
The LTC3568 is tested in a feedback loop which servos V
FB
to the
midpoint for the error amplifier (V
ITH
= 0.6V).
Note 4:
Dynamic supply current is higher due to the internal gate charge
being delivered at the switching frequency.
Note 5:
T
J
is calculated from the ambient T
A
and power dissipation P
D
according to the following formula:
T
J
= T
A
+ (P
D
• 43°C/W)
Note 6:
Switch on-resistance is guaranteed by correlation to wafer level
measurements.
Note 7:
4MHz operation is guaranteed by design but not production tested
and is subject to duty cycle limitations (see Applications Information).
Note 8:
This IC includes overtemperature protection that is intended
to protect the device during momentary overload conditions. Junction
temperature will exceed 125°C when overtemperature protection is active.
Continuous operation above the specified maximum operating junction
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