LTC3561A
3
3561afa
For more information www.linear.com/LTC3561A
ELECTRICAL CHARACTERISTICS
The ● denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 3.6V, R
T
= 125k unless otherwise specified. (Note 2)
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
I
S
Input DC Supply Current (Note 4)
Active Mode
Shutdown
V
FB
= 0.75V
V
SHDN/RT
= 3.6V
330
0.1
450
1
µA
µA
V
SHDN/RT
Shutdown Threshold High Active
Oscillator Resistor
V
IN
– 0.6
125k
V
IN
– 0.4
1M
V
Ω
f
OSC
Oscillator Frequency R
T
= 125k
(Note 7)
2.25 2.5 2.8
4
MHz
MHz
I
LIM
Peak Switch Current Limit V
FB
= 0.5V 1.3 2.0 2.5 A
R
DS(ON)
Top Switch On-Resistance (Note 6) 0.15 0.18 Ω
Bottom Switch On-Resistance (Note 6) 0.13 0.16 Ω
I
SW(LKG)
Switch Leakage Current V
IN
= 5V, V
SHDN/RT
= 3.6V, V
SW
= 0V or 5V 0.01 1 µA
V
UVLO
Undervoltage Lockout Threshold V
IN
Ramping Down 1.8 2.1 2.4 V
t
SOFT-START
10% to 90% of Regulation 0.5 0.8 1 ms
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 LTC3561AEDD is guaranteed to meet specified performance
specifications from 0°C to 85°C junction temperature. Specifications over
the –40°C to 125°C operating junction temperature range are assured by
design, characterization and correlation with statistical process controls.
The LTC3561AIDD is guaranteed over the full –40°C to 125°C operating
junction temperature range.
Note 3: The LTC3561A is tested in a feedback loop which servos V
FB
to the
midpoint for the error amplifier (V
ITH
= 0.7V).
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 formulas:
T
J
= T
A
+ (P
D
• 43°C/W)
Note 6: Switch on-resistance is sampled at wafer level measurements and
assured by design, characterization and correlation with statistical process
controls.
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
temperature may impair device reliability.
TYPICAL PERFORMANCE CHARACTERISTICS
T
A
= 25°C, V
IN
= 3.6V, f
O
= 1MHz, unless otherwise noted.
Efficiency vs Input Voltage Efficiency vs Output Current Efficiency vs Output Current
INPUT VOLTAGE (V)
2.5
50
60
70
80
3.0
3.5
4.0 4.5
3561A G01
5.0
90
100
55
65
75
85
95
5.5
I
OUT
= 100mA
V
OUT
= 1.8V
I
OUT
= 10mA
I
OUT
= 1A
OUTPUT CURRENT (mA)
1 10
0
EFFICIENCY (%)
40
30
1000100 10000
3561A G02
20
10
60
50
80
70
90
V
OUT
= 1.8V
V
IN
= 2.7V
V
IN
= 3.6V
V
IN
= 4.2V
OUTPUT CURRENT (mA)
1 10
0
EFFICIENCY (%)
40
30
1000100 10000
3561A G03
20
10
60
50
80
70
90
V
OUT
= 1.5V
V
IN
= 2.7V
V
IN
= 3.6V
V
IN
= 4.2V
