LTC3025-1/LTC3025-2/
LTC3025-3/LTC3025-4
1
30251234ff
Typical applicaTion
FeaTures
applicaTions
DescripTion
500mA Micropower
VLDO Linear Regulators
The LTC
®
3025-X is a micropower, VLDO™ (very low drop-
out) linear regulator which operates from input voltages as
low as 0.9V. The device is capable of supplying 500mA of
output current with a typical dropout voltage of only 85mV.
A BIAS supply is required to run the internal reference and
LDO circuitry while output current comes directly from the
IN supply for high efficiency regulation. The LTC3025-1
features an adjustable output with a low 0.4V reference
while the LTC3025-2, LTC3025-3, and LTC3025-4 have
fixed 1.2V, 1.5V and 1.8V output voltages respectively.
The LTC3025-X’s low quiescent current makes it an ideal
choice for use in battery-powered systems. For 3-cell NiMH
and single cell Li-Ion applications, the BIAS voltage can
be supplied directly from the battery while the input can
come from a high efficiency buck regulator, providing a
high efficiency, low noise output.
Other features include high output voltage accuracy,
excellent transient response, stability with ultralow ESR
ceramic capacitors as small as 1µF, short-circuit and
thermal overload protection and output current limiting.
The LTC3025-X is available in a tiny, low profile (0.75mm)
6-lead DFN (2mm × 2mm) package.
1.2V Output Voltage from 1.5V Input Supply
n Wide Input Voltage Range: 0.9V to 5.5V
n Stable with Ceramic Capacitors
n Very Low Dropout: 85mV at 500mA
n Adjustable Output Range: 0.4V to 3.6V (LTC3025-1)
n Fixed Output: 1.2V (LTC3025-2), 1.5V (LTC3025-3),
1.8V (LTC3025-4)
n ±2% Voltage Accuracy over Temperature,
Supply and Load
n Low Noise: 80µVRMS (10Hz to 100kHz)
n BIAS Voltage Range: 2.5V to 5.5V
n Fast Transient Recovery
n Shutdown Disconnects Load from VIN and VBIAS
n Low Operating Current: IIN = 4µA, IBIAS = 50µA Typ
n Low Shutdown Current: IIN = 1µA, IBIAS = 0.01µA Typ
n Output Current Limit
n Thermal Overload Protection
n Available in 6-Lead (2mm × 2mm) DFN Package
n Low Power Handheld Devices
n Low Voltage Logic Supplies
n DSP Power Supplies
n Cellular Phones
n Portable Electronic Equipment
n Handheld Medical Instruments
n Post Regulator for Switching Supply Noise Rejection
1MHz VIN Supply Rejection
LTC3025-2
BIAS
0.1µF
1.5V
1µF
0.1µF
Li-Ion
OR
3-CELL
NiMH
IN
SHDN
OUT VOUT = 1.2V
IOUT ≤ 500mA
30251234 TA01
SENSE
GNDOFF ON
1.5V HIGH
EFFICIENCY
DC/DC
BUCK
VIN (V)
1.2
0
REJECTION (dB)
5
15
20
25
50
35
1.6 2.0 2.2
30251234 TA01b
10
40
45
30
1.4 1.8 2.4 2.6
BIAS = 3.6V
VOUT = 1.2V
IOUT = 100mA
IOUT = 300mA
COUT = 1µF
COUT = 10µF
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and VLDO
and ThinSOT are trademarks of Linear Technology Corporation. All other trademarks are the
property of their respective owners. Protected by U.S. Patents including 7224204, 7218082.
LTC3025-1/LTC3025-2/
LTC3025-3/LTC3025-4
2
30251234ff
pin conFiguraTionabsoluTe MaxiMuM raTings
VBIAS, VIN to GND ......................................... –0.3V to 6V
SHDN to GND ............................................... –0.3V to 6V
SENSE, ADJ to GND ..................................... –0.3V to 6V
VOUT ........................................ –0.3V to VIN + 0.3V or 6V
Operating Junction Temperature Range
(Note 3) .................................................. –40°C to 125°C
Storage Temperature Range ................... –65°C to 125°C
Output Short-Circuit Duration .......................... Indefinite
(Notes 1, 2)
TOP VIEW
7
DC6 PACKAGE
6-LEAD (2mm × 2mm) PLASTIC DFN
4
5
6
3
2
1BIAS
GND
IN
SHDN
ADJ/SENSE*
OUT
TJMAX = 125°C, θJA = 102°C/W, θJC = 20°C/W
EXPOSED PAD (PIN 7) IS GND, MUST BE SOLDERED TO PCB
*ADJ FOR LTC3025-1, SENSE FOR LTC3025-2, LTC3025-3, LTC3025-4
orDer inForMaTion
LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE
LTC3025EDC-1#PBF LTC3025EDC-1#TRPBF LDDW 6-Lead (2mm × 2mm) Plastic DFN –40°C to 125°C
LTC3025IDC-1#PBF LTC3025IDC-1#TRPBF LDDW 6-Lead (2mm × 2mm) Plastic DFN –40°C to 125°C
LTC3025EDC-2#PBF LTC3025EDC-2#TRPBF LDMK 6-Lead (2mm × 2mm) Plastic DFN –40°C to 125°C
LTC3025IDC-2#PBF LTC3025IDC-2#TRPBF LDMK 6-Lead (2mm × 2mm) Plastic DFN –40°C to 125°C
LTC3025EDC-3#PBF LTC3025EDC-3#TRPBF LDQS 6-Lead (2mm × 2mm) Plastic DFN –40°C to 125°C
LTC3025IDC-3#PBF LTC3025IDC-3#TRPBF LDQS 6-Lead (2mm × 2mm) Plastic DFN –40°C to 125°C
LTC3025EDC-4#PBF LTC3025EDC-4#TRPBF LDPQ 6-Lead (2mm × 2mm) Plastic DFN –40°C to 125°C
LTC3025IDC-4#PBF LTC3025IDC-4#TRPBF LDPQ 6-Lead (2mm × 2mm) Plastic DFN –40°C to 125°C
LEAD BASED FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE
LTC3025EDC-1 LTC3025EDC-1#TR LDDW 6-Lead (2mm × 2mm) Plastic DFN –40°C to 125°C
LTC3025IDC-1 LTC3025IDC-1#TR LDDW 6-Lead (2mm × 2mm) Plastic DFN –40°C to 125°C
LTC3025EDC-2 LTC3025EDC-2#TR LDMK 6-Lead (2mm × 2mm) Plastic DFN –40°C to 125°C
LTC3025IDC-2 LTC3025IDC-2#TR LDMK 6-Lead (2mm × 2mm) Plastic DFN –40°C to 125°C
LTC3025EDC-3 LTC3025EDC-3#TR LDQS 6-Lead (2mm × 2mm) Plastic DFN –40°C to 125°C
LTC3025IDC-3 LTC3025IDC-3#TR LDQS 6-Lead (2mm × 2mm) Plastic DFN –40°C to 125°C
LTC3025EDC-4 LTC3025EDC-4#TR LDPQ 6-Lead (2mm × 2mm) Plastic DFN –40°C to 125°C
LTC3025IDC-4 LTC3025IDC-4#TR LDPQ 6-Lead (2mm × 2mm) Plastic DFN –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/
LTC3025-1/LTC3025-2/
LTC3025-3/LTC3025-4
3
30251234ff
elecTrical characTerisTics
The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VIN = 1.5V, VBIAS = 3.6V, COUT = 1µF, CIN = 0.1µF, CBIAS = 0.1µF
(all capacitors ceramic) unless otherwise noted. (Note 3)
PARAMETER CONDITIONS MIN TYP MAX UNITS
VIN Operating Voltage (Note 4) LTC3025-1 l0.9 5.5 V
LTC3025-2 l1.4 5.5 V
LTC3025-3 l1.7 5.5 V
LTC3025-4 l2.0 5.5 V
VBIAS Operating Voltage (Note 4) LTC3025-1 l2.5 5.5 V
LTC3025-2 l2.7 5.5 V
LTC3025-3 l3.0 5.5 V
LTC3025-4 l3.3 5.5 V
VBIAS Undervoltage Lockout l2.2 2.5 V
VIN Operating Current IOUT = 10µA, VOUT = 1.2V, LTC3025-1 l4 10 µA
VIN Operating Current IOUT = 0µA, LTC3025-2/LTC3025-3/LTC3025-4 l4 10 µA
VBIAS Operating Current IOUT = 10µA, VOUT = 1.2V, LTC3025-1 l50 80 µA
VBIAS Operating Current IOUT = 0µA, LTC3025-2/LTC3025-3/LTC3025-4 l50 80 µA
VIN Shutdown Current VSHDN = 0V 1 5 µA
VBIAS Shutdown Current VSHDN = 0V 0.01 1 µA
VADJ Regulation Voltage (Note 5) 1mA ≤ IOUT ≤ 500mA, VOUT = 1.2V, 1.5V ≤ VIN ≤ 5V, LTC3025-1
1mA ≤ IOUT ≤ 500mA, VOUT = 1.2V, 1.5V ≤ VIN ≤ 5V, LTC3025-1
l
0.395
0.392
0.4
0.4
0.405
0.408
V
V
VSENSE Regulation Voltage (Note 5) 1mA ≤ IOUT ≤ 500mA, 1.5V ≤ VIN ≤ 5V, LTC3025-2
1mA ≤ IOUT ≤ 500mA, 1.5V ≤ VIN ≤ 5V, LTC3025-2
l
1.185
1.176
1.2
1.2
1.215
1.224
V
V
VSENSE Regulation Voltage (Note 5) 1mA ≤ IOUT ≤ 500mA, 1.7V ≤ VIN ≤ 5V, LTC3025-3
1mA ≤ IOUT ≤ 500mA, 1.7V ≤ VIN ≤ 5V, LTC3025-3
l
1.481
1.470
1.5
1.5
1.519
1.530
V
V
VSENSE Regulation Voltage (Note 5) 1mA ≤ IOUT ≤ 500mA, 2.0V ≤ VIN ≤ 5V, LTC3025-4
1mA ≤ IOUT ≤ 500mA, 2.0V ≤ VIN ≤ 5V, LTC3025-4
l
1.777
1.764
1.8
1.8
1.823
1.836
V
V
IADJ ADJ Input Current VADJ = 0.45V, LTC3025-1 –50 0 50 nA
OUT Load Regulation (Referred to ADJ Pin) ∆IOUT = 1mA to 500mA, LTC3025-1 –0.35 mV
OUT Load Regulation ∆IOUT = 1mA to 500mA, LTC3025-2
∆IOUT = 1mA to 500mA, LTC3025-3
∆IOUT = 1mA to 500mA, LTC3025-4
–1
–1.3
–1.5
mV
mV
mV
VIN Line Regulation (Referred to ADJ Pin) VIN = 1.5V to 5V, VBIAS = 3.6V, VOUT = 1.2V,
IOUT = 1mA, LTC3025-1
0.07 mV
VIN Line Regulation VIN = 1.5V to 5V, VBIAS = 3.6V, IOUT = 1mA, LTC3025-2
VIN = 1.8V to 5V, VBIAS = 3.6V, IOUT = 1mA, LTC3025-3
VIN = 2.1V to 5V, VBIAS = 3.6V, IOUT = 1mA, LTC3025-4
0.21
0.26
0.32
mV
mV
mV
VBIAS Line Regulation VIN = 1.5V, VBIAS = 2.7V to 5V, VOUT = 1.2V, IOUT = 1mA,
LTC3025-1
l4.5 16.5 mV
VBIAS Line Regulation VIN = 1.5V, VBIAS = 2.7V to 5V, IOUT = 1mA, LTC3025-2
VIN = 1.8V, VBIAS = 3.0V to 5V, IOUT = 1mA, LTC3025-3
VIN = 2.1V, VBIAS = 3.3V to 5V, IOUT = 1mA, LTC3025-4
l
l
l
4.5
4.5
4.5
16.5
16.5
16.5
mV
mV
mV
VIN to VOUT Dropout Voltage (Notes 4, 6) VBIAS = 3V, VIN = 1.5V, IOUT = 500mA,
VADJ = 0.37V(LTC3025-1), VSENSE = 1.15V(LTC3025-2)
l
85 120
170
mV
mV
VIN to VOUT Dropout Voltage (Notes 4, 6) VBIAS = 3.1V, VIN = 1.7V, IOUT = 500mA,
VSENSE = 1.45V(LTC3025-3)
l
90 130
185
mV
mV
VIN to VOUT Dropout Voltage (Notes 4, 6) VBIAS = 3.4V, VIN = 2.0V, IOUT = 500mA,
VSENSE = 1.75V(LTC3025-4)
l
90 130
185
mV
mV
VBIAS to VOUT Dropout Voltage (Note 4) LTC3025-1 l1.5 V
LTC3025-1/LTC3025-2/
LTC3025-3/LTC3025-4
4
30251234ff
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: 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.
Note 3: The LTC3025-X regulators are tested and specified under pulse
load conditions such that TJ ≈ TA. The LTC3025E-X are guaranteed to
meet performance specifications from 0°C and 125°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 LTC3025I-X are guaranteed to meet performance specifications over
the full –40°C to 125°C operating junction temperature range.
Note 4: For the LTC3025-1, a regulated output voltage will only be available
when the minimum IN and BIAS operating voltages as well as the IN to
OUT and BIAS to OUT dropout voltages are all satisfied. For the
LTC3025-2/LTC3025-3/LTC3025-4 the minimum IN operating voltage
assumes IOUT = 500mA. For correct regulation at IOUT < 500mA the
minimum IN operating voltage decreases to the maximum VSENSE
Regulation Voltage as IOUT decreases to 0mA (i.e. VINMIN = 1.312V at IOUT
= 250mA for the LTC3025-2).
Note 5: Operating conditions are limited by maximum junction
temperature. The regulated output voltage specification will not apply
for all possible combinations of input voltage and output current. When
operating at maximum input voltage, the output current range must be
limited. When operating at maximum output current, the input voltage
range must be limited.
Note 6: Dropout voltage is minimum input to output voltage differential
needed to maintain regulation at a specified output current. In dropout, the
output voltage will be equal to VIN – VDROPOUT.
The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VIN = 1.5V, VBIAS = 3.6V, COUT = 1µF, CIN = 0.1µF, CBIAS = 0.1µF
(all capacitors ceramic) unless otherwise noted. (Note 3)
elecTrical characTerisTics
PARAMETER CONDITIONS MIN TYP MAX UNITS
IOUT Continuous Output Current l500 mA
IOUT Current Limit VADJ = 0V(LTC3025-1),
VSENSE = 0V(LTC3025-2/LTC3025-3/LTC3025-4)
1130 mA
en Output Voltage Noise f = 10Hz to 100kHz, IOUT = 300mA 80 µVRMS
VIH SHDN Input High Voltage l0.9 V
VIL SHDN Input Low Voltage l0.3 V
IIH SHDN Input High Current SHDN = 1.2V –1 1 µA
IL SHDN Input Low Current SHDN = 0V –1 1 µA
LTC3025-1/LTC3025-2/
LTC3025-3/LTC3025-4
5
30251234ff
VIN No Load Operating Current
VIN Shutdown Current
Adjust Voltage vs Temperature
SHDN Threshold vs Temperature
Current Limit vs VIN Voltage
Burst Mode DC/DC Buck Ripple
Rejection
Typical perForMance characTerisTics
VIN (V)
0.5
10 125°C
85°C
25°C –40°C
12
14
4.5
30251234 G04
8
6
1.5 2.5 3.5 5.5
4
2
0
IIN (µA)
VBIAS = 5V
VOUT = 0.8V
VIN (V)
0.5
5
25°C
–40°C
6
7
4.5
30251234 G05
4
3
1.5 2.5 3.5 5.5
2
1
0
IIN (µA)
85°C
VBIAS = 5V
TEMPERATURE (°C)
–50
395
ADJUST VOLTAGE (mV)
396
398
399
400
405
402
050 75
30251234 G06
397
403
404
401
–25 25 100 125
VBIAS = 3.6V
VIN = 1.5V
IOUT = 10µA
TEMPERATURE (°C)
–50
0
SHDN THRESHOLD (mV)
100
300
400
500
1000
700
050 75
30251234 G07
200
800
900
600
–25 25 100 125
VBIAS = 2.5V
VBIAS = 5V
VIN (V)
0
CURRENT LIMIT (mA)
600
800
1000
35
30251234 G08
400
200
01 2 4
1200
1400
1600
6
VIN
AC
100mV/DIV
VOUT
AC
10mV/DIV
VIN = 1.8V
VOUT = 1.5V
COUT = 1µF
IOUT = 50mA
10µs/DIV 30251234 G09
(TA = 25°C unless otherwise noted)
VIN to VOUT Dropout Voltage
vs IOUT
Operating BIAS Current
vs Output Current BIAS No Load Operating Current
IOUT (mA)
0
DROPOUT VOLTAGE (mV)
40
80
120
20
60
100
100 200 300 400
30251234 G01
500500 150 250 350 450
TA = –40°C
TA = 125°C
TA = 25°C
VBIAS = 2.8V
VIN = 1.4V
IOUT (mA)
0.01
IBIAS (µA)
150
200
250
10 1000
30251234 G02
100
50
00.1 1 100
300
350
500
400
450
–40°C
125°C
25°C
VBIAS (V)
2.5
IBIAS (µA)
30
40
45
30251234 G03
20
10
03 3.5 4.5
60
50
70
80
5.5
VIN = 1.5V
VOUT = 1.2V
125°C
25°C
–40°C
LTC3025-1/LTC3025-2/
LTC3025-3/LTC3025-4
6
30251234ff
Typical perForMance characTerisTics
Transient Response
250mA
10mA
IOUT
VOUT
AC
10mV/DIV
VIN = 1.5V
VOUT = 1.2V
VBIAS = 3.6V
COUT = 1µF
100µs/DIV 30251234 G13
VIN to VOUT Dropout Voltage
vs VIN (25°C) LTC3025-1
(TA = 25°C unless otherwise noted)
VIN to VOUT Dropout Voltage
vs VIN (90°C) LTC3025-1
VIN (V)
1
0
DROPOUT (V)
0.025
0.075
0.100
0.125
0.300
0.175
233.5
30251234 G14
0.050
0.200
0.225
0.250
0.275
0.150
1.5 2.5 44.5
VADJ = 0.385
IOUT = 500mA
TA = 25°C
BIAS = 2.7V
BIAS = 3V BIAS = 3.3V
BIAS = 3.8V
BIAS = 5V
VIN (V)
1
0
DROPOUT (V)
0.025
0.075
0.100
0.125
0.300
0.175
233.5
30251234 G15
0.050
0.200
0.225
0.250
0.275
0.150
1.5 2.5 44.5
VADJ = 0.385
IOUT = 500mA
TA = 90°C
BIAS = 2.7V
BIAS = 3.8V
BIAS = 5V
BIAS = 3V
BIAS = 3.3V
VIN Ripple Rejection
vs Frequency
BIAS Ripple Rejection
vs Frequency
3MHz VIN Supply Rejection
FREQUENCY (Hz)
100
50
60
70
1M
30251234 G10
40
30
1k 10k 100k 10M
20
10
0
REJECTION (dB)
VBIAS = 3.6V
VIN = 1.5V
VOUT = 1.2V
IOUT = 100mA
COUT = 10µF
COUT = 1µF
FREQUENCY (Hz)
100
50
60
70
1M
30251234 G11
40
30
1k 10k 100k 10M
20
10
0
REJECTION (dB)
VBIAS = 3.6V
VIN = 1.5V
VOUT = 1.2V
IOUT = 100mA
COUT = 10µF
COUT = 1µF
VIN (V)
1.2
0
REJECTION (dB)
5
15
20
25
50
35
1.6 2.0 2.2
30251234 G12
10
40
45
30
1.4 1.8 2.4 2.6
VBIAS = 3.6V
VOUT = 1.2V
IOUT = 100mA
IOUT = 300mA
COUT = 1µF
COUT = 10µF
LTC3025-1/LTC3025-2/
LTC3025-3/LTC3025-4
7
30251234ff
pin FuncTions
BIAS (Pin 1): BIAS Input Voltage. BIAS provides internal
power for LTC3025-X circuitry. The BIAS pin should be
locally bypassed to ground if the LTC3025-X is more than a
few inches away from another source of bulk capacitance.
In general, the output impedance of a battery rises with
frequency, so it is usually advisable to include an input
bypass capacitor in battery-powered circuits. A capacitor
in the range of 0.01µF to 0.1µF is usually sufficient.
GND (Pin 2): Ground. Connect to a ground plane.
IN (Pin 3): Input Supply Voltage. The output load current
is supplied directly from IN. The IN pin should be locally
bypassed to ground if the LTC3025-X is more than a few
inches away from another source of bulk capacitance.
In general, the output impedance of a battery rises with
frequency, so it is usually advisable to include an input
bypass capacitor when supplying IN from a battery. A
capacitor in the range of 0.1µF to 1µF is usually sufficient.
OUT (Pin 4): Regulated Output Voltage. The OUT pin
supplies power to the load. A minimum ceramic output
capacitor of at least 1µF is required to ensure stability.
Larger output capacitors may be required for applications
with large transient loads to limit peak voltage transients.
See the Applications Information section for more informa-
tion on output capacitance.
ADJ (Pin 5) LTC3025-1: Adjust Input. This is the input to
the error amplifier. The ADJ pin reference voltage is 0.4V
referenced to ground. The output voltage range is 0.4V to
3.6V and is typically set by connecting ADJ to a resistor
divider from OUT to GND. See Figure 2.
SENSE (Pin 5) LTC3025-2, LTC3025-3, LTC3025-4: Output
Sense. The sense is the input to the resistor divider driving
the error amplifier. Optimum regulation will be obtained at
the point where SENSE is connected to OUT. The SENSE pin
bias current is 10µA at the nominal rated output voltage.
SHDN (Pin 6): Shutdown Input, Active Low. This pin is
used to put the LTC3025-X into shutdown. The SHDN pin
current is typically less than 10nA. The SHDN pin cannot
be left floating and must be tied to a valid logic level (such
as BIAS) if not used.
GND (Exposed Pad Pin 7): Ground and Heat Sink. Must
be soldered to PCB ground plane or large pad for optimal
thermal performance.
block DiagraM
3
1
6
24
5
IN
OUT
6µA
ADJ
GND
SHDN
BIAS
REFERENCE
SHDN 0.4V
SOFT-START
–
+3
1
6
24
5
IN
OUT
6µA
30251234 BD
SENSE
GND
SHDN
BIAS
REFERENCE
SHDN 0.4V
SOFT-START
–
+
R1
40k
R2
80k (LTC3025-2)
110k (LTC3025-3)
140k (LTC3025-4)
LTC3025-1 LTC3025-2, LTC3025-3, LTC3025-4
LTC3025-1/LTC3025-2/
LTC3025-3/LTC3025-4
8
30251234ff
applicaTions inForMaTion
Operation (Refer to Block Diagram)
The LTC3025-X is a micropower, VLDO (very low dropout)
linear regulator which operates from input voltages as low
as 0.9V. The device provides a highly accurate output that
is capable of supplying 500mA of output current with a
typical dropout voltage of only 85mV. A single ceramic
capacitor as small as 1µF is all that is required for output
bypassing. A low reference voltage allows the LTC3025-1
output to be programmed to much lower voltages than
available in common LDOs (range of 0.4V to 3. 6V). The
LTC3025-2/LTC3025-3/LTC3025-4 have fixed outputs of
1.2V, 1.5V and 1.8V respectively, eliminating the need for
an external resistor divider.
As shown in the Block Diagram, the BIAS input supplies
the internal reference and LDO circuitry while all output
current comes directly from the IN input for high efficiency
regulation. The low quiescent supply currents IIN = 4µA,
IBIAS = 50µA drop to IIN = 1µA, IBIAS = 0.01µA typical in
shutdown making the LTC3025-X an ideal choice for use
in battery-powered systems.
The device includes current limit and thermal overload
protection. The fast transient response of the follower
output stage overcomes the traditional tradeoff between
dropout voltage, quiescent current and load transient
response inherent in most LDO regulator architectures.
The LTC3025-X also includes overshoot detection circuitry
which brings the output back into regulation when going
from heavy to light output loads (see Figure 1).
Figure 1. LTC3025-X Transient Response
300mA
0mA
IOUT
VOUT
AC
20mV/DIV
VIN = 1.5V
VOUT = 1.2V
VBIAS = 3.6V
COUT = 1µF
100µs/DIV 30251234 F01
Adjustable Output Voltage (LTC3025-1)
The output voltage is set by the ratio of two external resis-
tors as shown in Figure 2. The device servos the output
to maintain the ADJ pin voltage at 0.4V (referenced to
ground). Thus, the current in R1 is equal to 0.4V/R1. For
good transient response, stability, and accuracy, the current
in R1 should be at least 8µA, thus the value of R1 should
be no greater than 50k. The current in R2 is the current in
R1 plus the ADJ pin bias current. Since the ADJ pin bias
current is typically <10nA, it can be ignored in the output
voltage calculation. The output voltage can be calculated
using the formula in Figure 2. Note that in shutdown the
output is turned off and the divider current will be zero
once COUT is discharged.
The LTC3025-1 operates at a relatively high gain of –0.7µV/
mA referred to the ADJ input. Thus a load current change
of 1mA to 500mA produces a –0.35mV drop at the ADJ
input. To calculate the change referred to the output
simply multiply by the gain of the feedback network
(i. e. ,1 + R2/R1). For example, to program the output for
1.2V choose R2/R1 = 2. In this example, an output current
change of 1mA to 500mA produces –0.35mV • (1 + 2) =
1.05mV drop at the output.
Because the ADJ pin is relatively high impedance (depend-
ing on the resistor divider used), stray capacitance at this
pin should be minimized (<10pF) to prevent phase shift
in the error amplifier loop. Additionally, special attention
should be given to any stray capacitances that can couple
external signals onto the ADJ pin producing undesirable
output ripple. For optimum performance connect the ADJ
pin to R1 and R2 with a short PCB trace and minimize all
other stray capacitance to the ADJ pin.
Figure 2. Programming the LTC3025-1
( )
OUT
R1
R2
30251234 F02
COUT
R2
R1
VOUT = 0.4V 1 +
ADJ
GND
LTC3025-1/LTC3025-2/
LTC3025-3/LTC3025-4
9
30251234ff
applicaTions inForMaTion
Output Capacitance and Transient Response
The LTC3025-X is designed to be stable with a wide range
of ceramic output capacitors. The ESR of the output capaci-
tor affects stability, most notably with small capacitors. A
minimum output capacitor of 1µF with an ESR of 0.05Ω or
less is recommended to ensure stability. The LTC3025-X is
a micropower device and output transient response will be
a function of output capacitance. Larger values of output
capacitance decrease the peak deviations and provide im-
proved transient response for larger load current changes.
Note that bypass capacitors used to decouple individual
components powered by the LTC3025-X will increase the
effective output capacitor value. High ESR tantalum and
electrolytic capacitors may be used, but a low ESR ceramic
capacitor must be in parallel at the output. There is no
minimum ESR or maximum capacitor size requirements.
Extra consideration must be given to the use of ceramic
capacitors. Ceramic capacitors are manufactured with a
variety of dielectrics, each with different behavior across
temperature and applied voltage. The most common di-
electrics used are Z5U, Y5V, X5R and X7R. The Z5U and
Y5V dielectrics are good for providing high capacitances
in a small package, but exhibit large voltage and tem-
perature coefficients as shown in Figures 3 and 4. When
used with a 2V regulator, a 1µF Y5V capacitor can lose as
much as 75% of its initial capacitance over the operating
temperature range. The X5R and X7R dielectrics result in
more stable characteristics and are usually more suitable
for use as the output capacitor. The X7R type has better
stability across temperature, while the X5R is less expensive
and is available in higher values. In all cases, the output
capacitance should never drop below 0.4µF, or instability
or degraded performance may occur.
Figure 3. Ceramic Capacitor DC Bias Characteristics
Figure 4. Ceramic Capacitor Temperature Characteristics
DC BIAS VOLTAGE (V)
CHANGE IN VALUE (%)
30251234 F03
20
0
–20
–40
–60
–80
–100 04810
2 6
X5R
Y5V
BOTH CAPACITORS ARE 1µF,
10V, 0603 CASE SIZE
TEMPERATURE (°C)
–50
–100
CHANGE IN VALUE (%)
–80
–60
–40
–20
X5R
Y5V
20
–25 0 25 50
30251234 F04
75
0
BOTH CAPACITORS ARE 1µF,
10V, 0603 CASE SIZE
LTC3025-1/LTC3025-2/
LTC3025-3/LTC3025-4
10
30251234ff
applicaTions inForMaTion
Thermal Considerations
The power handling capability of the device will be limited
by the maximum rated junction temperature (125°C). The
power dissipated by the device will be the output current
multiplied by the input/output voltage differential:
(IOUT) (VIN – VOUT)
Note that the BIAS current is less than 500µA even under
heavy loads, so its power consumption can be ignored
for thermal calculations.
The LTC3025-X has internal thermal limiting designed to
protect the device during momentary overload conditions.
For continuous normal conditions, the maximum junction
temperature rating of 125°C must not be exceeded. It is
important to give careful consideration to all sources of
thermal resistance from junction to ambient. Additional
heat sources mounted nearby must also be considered.
For surface mount devices, heat sinking is accomplished
by using the heat-spreading capabilities of the PC board
and its copper traces. Copper board stiffeners and plated
through holes can also be used to spread the heat gener-
ated by power devices.
The LTC3025-X 2mm × 2mm DFN package is specified
as having a junction-to-ambient thermal resistance of
102°C/W, which assumes a minimal heat spreading cop-
per plane. The actual thermal resistance can be reduced
substantially by connecting the package directly to a good
heat spreading ground plane. When soldered to 2500mm2
double-sided 1 oz. copper plane, the actual junction-to-
ambient thermal resistance can be less than 60°C/W.
Calculating Junction Temperature
Example: Given an output voltage of 1.2V, an input voltage
of 1.8V to 3V, an output current range of 0mA to 100mA
and a maximum ambient temperature of 50°C, what will
the maximum junction temperature be?
The power dissipated by the device will be equal to:
IOUT(MAX) (VIN(MAX) – VOUT)
where:
IOUT(MAX) = 100mA
VIN(MAX) = 3V
So:
P = 100mA(3V – 1.2V) = 0.18W
Even under worst-case conditions, the LTC3025-X’s BIAS
pin power dissipation is only about 1mW, thus can be ig-
nored. Assuming a junction-to-ambient thermal resistance
of 102°C/W, the junction temperature rise above ambient
will be approximately equal to:
0.18W(102°C/W) = 18.4°C
The maximum junction temperature will then be equal to
the maximum junction temperature rise above ambient
plus the maximum ambient temperature or:
TJ = 50°C + 18.4°C = 68.4°C
Short-Circuit/Thermal Protection
The LTC3025-X has built-in short-circuit current limiting
as well as overtemperature protection. During short-circuit
conditions, internal circuitry automatically limits the output
current to approximately 1130mA. At higher temperatures,
or in cases where internal power dissipation causes exces-
sive self heating on chip, the thermal shutdown circuitry
will shut down the LDO when the junction temperature
exceeds approximately 150°C. It will re enable the LDO
once the junction temperature drops back to approximately
140°C. The LTC3025-X will cycle in and out of thermal
shutdown without latch-up or damage until the overstress
condition is removed. Long term overstress (TJ > 125°C)
should be avoided as it can degrade the performance or
shorten the life of the part.
LTC3025-1/LTC3025-2/
LTC3025-3/LTC3025-4
11
30251234ff
Figure 5. Output Start-Up and Shutdown
OFF
1.2V
0V
ON
SHDN
VOUT
200mV/DIV
TA = 25°C
VIN = 1.5V
VBIAS = 3.6V
COUT = 1µF
RLOAD = 4Ω
500µs/DIV 30251234 F05
applicaTions inForMaTion
Soft-Start Operation
The LTC3025-X includes a soft-start feature to prevent
excessive current flow during start-up. When the LDO is
enabled, the soft-start circuitry gradually increases the
LDO reference voltage from 0V to 0.4V over a period of
about 600µs. There is a short 700µs delay from the time
the part is enabled until the LDO output starts to rise. Fig-
ure 5 shows the start-up and shutdown output waveform.
VOUT Start-Up and Supply Sequencing
During power-up, the output shutdown circuitry is not
active below VIN of about 0.65V DC (typical). As a result,
the output voltage can drift up during power-up due to
leakage current (<1 mA typical) from VIN to VOUT
. At 0.9V
input, the shutdown circuitry is active and the output is
actively held off. This usually causes no circuit problems
and is similar to 3-terminal regulators such as the LT3080,
LT1086 and LT317 which have no ground pin and can have
the output rise under some conditions. A slowly rising
VIN with the part enabled may result in non-monotonic
ramping of VOUT due to LDO circuitry becoming active at
VIN of about 0.65V (typical) as well.
With fast rising inputs (>1V/ms) or with sufficient resis-
tive load on VOUT
, output voltage rise during power-up
is reduced or eliminated. Such conditions also reduce or
eliminate non-monotonic initial power-up with the part
enabled. If VBIAS is sequenced up before VIN, the leakage
current from VIN to VOUT may increase until the shutdown
circuitry is active at a VIN of about 0.65V typical. Thus,
to minimize VOUT rise during start-up, sequence up VIN
before VBIAS. At VIN = 0.9V, the output is actively held off
in shutdown or it is actively held on when enabled under
all conditions.
LTC3025-1/LTC3025-2/
LTC3025-3/LTC3025-4
12
30251234ff
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no representa-
tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.
package DescripTion
DC Package
6-Lead Plastic DFN (2mm × 2mm)
(Reference LTC DWG # 05-08-1703 Rev B)
2.00 ±0.10
(4 SIDES)
NOTE:
1. DRAWING TO BE MADE A JEDEC PACKAGE OUTLINE M0-229 VARIATION OF (WCCD-2)
2. DRAWING NOT TO SCALE
3. ALL DIMENSIONS ARE IN MILLIMETERS
4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE
MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE
5. EXPOSED PAD SHALL BE SOLDER PLATED
6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE
TOP AND BOTTOM OF PACKAGE
0.40 ± 0.10
BOTTOM VIEW—EXPOSED PAD
0.56 ± 0.05
(2 SIDES)
0.75 ±0.05
R = 0.125
TYP
R = 0.05
TYP
1.37 ±0.05
(2 SIDES)
1
3
64
PIN 1 BAR
TOP MARK
(SEE NOTE 6)
0.200 REF
0.00 – 0.05
(DC6) DFN REV B 1309
0.25 ± 0.05
0.50 BSC
0.25 ± 0.05
1.42 ±0.05
(2 SIDES)
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
0.61 ±0.05
(2 SIDES)
1.15 ±0.05
0.70 ±0.05
2.55 ±0.05
PACKAGE
OUTLINE
0.50 BSC
PIN 1 NOTCH
R = 0.20 OR
0.25 × 45°
CHAMFER
LTC3025-1/LTC3025-2/
LTC3025-3/LTC3025-4
13
30251234ff
revision hisTory
REV DATE DESCRIPTION PAGE NUMBER
E 07/10 Added (Note 3) notation to “The l denotes” statement in Electrical Characteristics section
Updated Pin 7 in Pin Functions
Added “VOUT Start-Up and Supply Sequencing” section
Updated Related Parts section
3, 4
7
11
14
F 04/11 Updated y-axis on graphs G14 and G15 6
(Revision history begins at Rev E)
LTC3025-1/LTC3025-2/
LTC3025-3/LTC3025-4
14
30251234ff
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com
LINEAR TECHNOLOGY CORPORATION 2007
LT 0411 REV F • PRINTED IN USA
relaTeD parTs
PART NUMBER DESCRIPTION COMMENTS
LT1761 100mA, Low Noise Micropower, LDO VIN: 1.8V to 20V, VOUT(MIN) = 1.22V, VDO = 0.30V, IQ = 20µA, ISD < 1µA,
VOUT = Adj, 1.5V, 1.8V, 2V, 2.5V, 2.8V, 3V, 3.3V, 5V, ThinSOT
TM
Package.
Low Noise < 20µVRMSP-P, Stable with 1µF Ceramic Capacitors
LT1762 150mA, Low Noise Micropower LDO VIN: 1.8V to 20V, VOUT(MIN) = 1.22V, VDO = 0.30V, IQ = 25µA, ISD < 1µA,
VOUT = Adj, 2.5V, 3V, 3.3V, 5V, MS8 Package. Low Noise < 20µVRMSP-P
LTC1844 150mA, Very Low Dropout LDO VIN: 1.6V to 6.5V, VOUT(MIN) = 1.25V, VDO = 0.08V, IQ = 40µA, ISD < 1µA,
VOUT = Adj, 1.5V, 1.8V, 2.5V, 2.8V, 3.3V, ThinSOT Package.
Low Noise < 30µVRMSP-P, Stable with 1µF Ceramic Capacitors
LT1962 300mA, Low Noise Micropower LDO VIN: 1.8V to 20V, VOUT(MIN) = 1.22V, VDO = 0.27V, IQ = 30µA, ISD < 1µA,
VOUT = 1.5, 1.8V, 2.5V, 3V, 3.3V, 5V, MS8 Package. Low Noise < 20µVRMSP-P
LT1964 200mA, Low Noise Micropower, Negative LDO VIN: –0.9V to –20V, VOUT(MIN) = –1.21V, VDO = 0.34V, IQ = 30µA, ISD < 3µA,
VOUT = Adj, –5V, ThinSOT Package.
Low Noise < 30µVRMSP-P, Stable with Ceramic Capacitors
LT3020 100mA, Low Voltage, VLDO VIN: 0.9V to 10V, VOUT(MIN) = 0.20V, VDO = 0.15V, IQ = 120µA, ISD < 3µA,
VOUT = Adj, DFN, MS8 Package
LTC3025 300mA Micropower VLDO Linear Regulator 45mV Dropout Voltage, Low Noise: 80µVRMS, VIN: 0.9V to 5.5V, Low IQ = 54µA,
2mm × 2mm 6-Lead DFN Package
LTC3026 1.5A, Low Input Voltage VLDO Regulator VIN: 1.14V to 3.5V (Boost Enabled), 1.14V to 5.5V (with External 5V Rail),
VDO = 0.1V, IQ = 950µA, Stable with 10µF Ceramic Capacitors,
DFN-10 and MSOP-10 Packages
Typical applicaTion
High Efficiency 1.5V Step-Down Converter with Efficient 1.2V VLDO Output
Efficiency vs Output Current
LTC3025-1
BIAS
0.1µF 1µF
IN
SHDN
OUT
80.6k
VOUT = 1.2V
IOUT ≤ 500mA
40.2k
30251234 TA02
ADJ
GND
1
3
6
4
5
2
OFF ON
VIN
CIN**
4.7µF
CER
VIN
2.7V
TO 5.5V
LTC3406-1.5
RUN
2.2µH*
*
**
†
MURATA LQH32CN2R2M33
TAIYO YUDEN JMK212BJ475MG
TAIYO YUDEN JMK316BJ106ML
SW
4
1
3
5
COUT†
10µF
CER
VOUT
1.5V
600mA
VOUT
GND
OUTPUT CURRENT (mA)
EFFICIENCY (%)
100
90
80
70
60
50
400.1 10 100 1000
30251234 TA03
1
LTC3406-1.5
VOUT = 1.5V
LTC3025-1
VOUT = 1.2V
VIN = 3.6V
