LT3028
Dual 100mA/500mA
Low Dropout, Low Noise,
Micropower Regulators with
Independent Inputs
FEATURES
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DESCRIPTIO
Low Noise: 20µV
RMS
(10Hz to 100kHz)
Low Quiescent Current: 30µA/Output
Independent Inputs
Wide Input Voltage Range: 1.8V to 20V
Output Current: 100mA/500mA
Very Low Shutdown Current: <0.1
µ
A
Low Dropout Voltage: 300mV/320mV at
100mA/500mA
Adjustable Outputs from 1.22V to 20V
Stable with as Low as 1µF/3.3µF Output Capacitor
Stable with Aluminum, Tantalum or
Ceramic Capacitors
Reverse-Battery Protected
No Protection Diodes Needed
Overcurrent and Overtemperature Protected
Tracking/Sequencing Capability
Thermally Enhanced 16-Lead TSSOP and 16-Lead
(5mm
×
3mm) DFN Packages
APPLICATIO S
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Cellular Phones
Pagers
Battery-Powered Systems
Frequency Synthesizers
Wireless Modems
Tracking/Sequencing Power Supplies
The LT
®
3028 is a dual, micropower, low noise, low drop-
out regulator with independent inputs. With an external
0.01µF bypass capacitor, output noise is a low 20µV
RMS
over a 10Hz to 100kHz bandwidth. Designed for use in
battery-powered systems, the low 30µA quiescent current
per output makes it an ideal choice. In shutdown, quies-
cent current drops to less than 0.1µA. Shutdown control
is independent for each output, allowing for flexibility in
power management. The device is capable of operating
over an input voltage range of 1.8V to 20V. Output 1 can
supply 500mA of output current with a dropout voltage of
320mV. The device can supply 100mA of output current
from Output 2 with a dropout voltage of 300mV. Quiescent
current is well controlled in dropout.
The LT3028 regulator is stable with output capacitors as
low as 1µF for the 100mA output and 3.3µF for the 500mA
output. Small ceramic capacitors can be used without the
series resistance required by other regulators.
Internal protection circuitry includes reverse-battery pro-
tection, current limiting and thermal limiting protection.
The device is available as an adjustable device with a 1.22V
reference voltage. The LT3028 regulator is available in the
thermally enhanced 16-lead TSSOP and 16-lead, low
profile (5mm
×
3mm
×
0.75mm) DFN packages.
, LTC and LT are registered trademarks of Linear Technology Corporation.
Protected by U.S. Patents including 6118263, 6144250.
TYPICAL APPLICATIO
V
IN1
3.7V TO
20V
IN1
1µF
SHDN1
BYP1
ADJ1
LT3028
IN2
1µF
SHDN2
GND
OUT2
OUT1
3.3V/2.5V Low Noise Regulators
0.01µF
422k
10µF
3.3V AT 500mA
20µV
RMS
NOISE
10Hz to 100kHz Output Noise
249k
2.5V AT 100mA
20µV
RMS
NOISE
V
OUT
100µV/DIV
V
IN2
2.9V TO
20V
0.01µF
BYP2
ADJ2
261k
10µF
249k
3028 TA01a
U
20µV
RMS
3028 TA01b
U
U
3028f
1
LT3028
ABSOLUTE
AXI U
RATI GS
IN1, IN2 Pin Voltage ..............................................
±20V
OUT1, OUT2 Pin Voltage .......................................
±20V
Input-to-Output Differential Voltage .......................
±20V
ADJ1, ADJ2 Pin Voltage .........................................
±7V
BYP1, BYP2 Pin Voltage .......................................
±0.6V
SHDN1, SHDN2 Pin Voltage .................................
±20V
Output Short-Circut Duration .......................... Indefinite
PACKAGE/ORDER I FOR ATIO
TOP VIEW
GND
BYP1
OUT1
OUT1
GND
OUT2
BYP2
GND
1
2
3
4
5
6
7
8
17
16 GND
15 ADJ1
14 SHDN1
13 IN1
12 IN2
11 SHDN2
10 ADJ2
9
GND
ORDER PART
NUMBER
LT3028EFE
LT3028IFE
FE PART
MARKING
3028EFE
3028IFE
FE PACKAGE
16-LEAD PLASTIC TSSOP
T
JMAX
= 150°C,
θ
JA
= 38°C/ W,
θ
JC
= 8°C/ W
EXPOSED PAD (PIN 17) IS GND
MUST BE SOLDERED TO PCB
Consult factory for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS
The
●
denotes specifications which apply over the full operating temperature range, otherwise specifications are T
A
= 25°C. (Note 2)
PARAMETER
Minimum Input Voltage
(Notes 3, 10)
ADJ1, ADJ2 Pin Voltage
(Notes 3, 4)
Line Regulation (Note 3)
Load Regulation (Note 3)
CONDITIONS
Output 2, I
LOAD
= 100mA
Output 1, I
LOAD
= 500mA
V
IN
= 2V, I
LOAD
= 1mA
Output 2, 2.3V < V
IN2
< 20V, 1mA < I
LOAD
< 100mA
Output 1, 2.3V < V
IN1
< 20V, 1mA < I
LOAD
< 500mA
∆V
IN
= 2V to 20V, I
LOAD
= 1mA
Output 2, V
IN2
= 2.3V,
∆I
LOAD
= 1mA to 100mA
V
IN2
= 2.3V,
∆I
LOAD
= 1mA to 100mA
Output 1, V
IN1
= 2.3V,
∆I
LOAD
= 1mA to 500mA
V
IN1
= 2.3V,
∆I
LOAD
= 1mA to 500mA
●
●
●
●
●
●
2
U
U
W
W W
U
W
(Note 1)
Operating Junction Temperature Range
(Note 2) ............................................ – 40°C to 125°C
Storage Temperature Range
FE Package ....................................... – 65°C to 150°C
DHC Package .................................... – 65°C to 125°C
Lead Temperature (Soldering, 10 sec).................. 300°C
TOP VIEW
BYP1
NC
OUT1
OUT1
GND
OUT2
OUT2
BYP2
1
2
3
4
5
6
7
8
17
16 ADJ1
15 SHDN1
14 IN1
13 IN1
12 IN2
11 IN2
10 SHDN2
9
ADJ2
ORDER PART
NUMBER
LT3028EDHC
LT3028IDHC
DHC PART
MARKING
3028
3028I
DHC PACKAGE
16-LEAD (5mm
×
3mm) PLASTIC DFN
T
JMAX
= 125°C,
θ
JA
= 40°C/ W,
θ
JC
= 10°C/ W
EXPOSED PAD (PIN 17) IS GND
MUST BE SOLDERED TO PCB
MIN
TYP
1.8
1.8
MAX
2.3
2.3
1.235
1.250
1.250
10
12
25
12
25
UNITS
V
V
V
V
V
mV
mV
mV
mV
mV
1.205
1.190
1.190
1.220
1.220
1.220
1
1
1
●
3028f
LT3028
ELECTRICAL CHARACTERISTICS
The
●
denotes specifications which apply over the full operating temperature range, otherwise specifications are T
A
= 25°C. (Note 2)
PARAMETER
Dropout Voltage
(Output 2)
V
IN2
= V
OUT2(NOMINAL)
(Notes 5, 6, 10)
CONDITIONS
I
LOAD
= 1mA
I
LOAD
= 1mA
I
LOAD
= 10mA
I
LOAD
= 10mA
I
LOAD
= 50mA
I
LOAD
= 50mA
I
LOAD
= 100mA
I
LOAD
= 100mA
Dropout Voltage
(Output 1)
V
IN1
= V
OUT1(NOMINAL)
(Notes 5, 6, 10)
I
LOAD
= 10mA
I
LOAD
= 10mA
I
LOAD
= 50mA
I
LOAD
= 50mA
I
LOAD
= 100mA
I
LOAD
= 100mA
I
LOAD
= 500mA
I
LOAD
= 500mA
GND Pin Current
(Output 2)
V
IN2
= V
OUT2(NOMINAL)
(Notes 5, 7)
GND Pin Current
(Output 1)
V
IN1
= V
OUT1(NOMINAL)
(Notes 5, 7)
I
LOAD
= 0mA
I
LOAD
= 1mA
I
LOAD
= 10mA
I
LOAD
= 50mA
I
LOAD
= 100mA
I
LOAD
= 0mA
I
LOAD
= 1mA
I
LOAD
= 50mA
I
LOAD
= 100mA
I
LOAD
= 250mA
I
LOAD
= 500mA
C
OUT
= 10µF, C
BYP
= 0.01µF, I
LOAD
= Full Current,
BW = 10Hz to 100kHz
ADJ1, ADJ2 (Notes 3, 8)
V
OUT
= Off to On
V
OUT
= On to Off
V
SHDN1
, V
SHDN2
= 0V
V
SHDN1
, V
SHDN2
= 20V
V
IN
= 6V, V
SHDN1
= 0V, V
SHDN2
= 0V
V
IN
= 2.72V (Avg), V
RIPPLE
= 0.5V
P-P
, f
RIPPLE
= 120Hz,
I
LOAD
= Full Current
Output 2, V
IN2
= 7V, V
OUT2
= 0V
V
IN2
= 2.3V,
∆V
OUT2
= – 0.1V
Output 1, V
IN1
= 7V, V
OUT1
= 0V
V
IN1
= 2.3V,
∆V
OUT1
= – 0.1V
Input Reverse Leakage Current
V
IN
= – 20V, V
OUT
= 0V
●
●
●
●
●
●
●
●
MIN
TYP
0.10
0.17
MAX
0.15
0.19
0.22
0.29
0.31
0.40
0.35
0.45
0.19
0.25
0.22
0.32
0.28
0.34
0.37
0.47
50
95
400
2
4
75
120
1.6
3
8
16
UNITS
V
V
V
V
V
V
V
V
V
V
V
V
V
V
V
V
µA
µA
µA
mA
mA
µA
µA
mA
mA
mA
mA
µV
RMS
●
0.24
●
0.30
●
0.12
●
0.17
●
0.21
●
0.32
●
●
●
●
●
●
●
●
●
●
●
●
25
60
230
1
2.2
30
65
1
2
5
10
20
30
0.25
0.80
0.65
0
1
0.01
55
65
500
110
1.3
520
Output Voltage Noise
ADJ1/ADJ2 Pin Bias Current
Shutdown Threshold
SHDN1/SHDN2 Pin Current
(Note 9)
Quiescent Current in Shutdown
Ripple Rejection
Current Limit
100
1.4
0.5
3.0
0.1
nA
V
V
µA
µA
µA
dB
mA
mA
A
mA
1
mA
Note 1:
Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2:
The LT3028 regulator is tested and specified under pulse load
conditions such that T
J
≈
T
A
. The LT3028E is guaranteed to meet
performance specifications from 0°C to 125°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 LT3028I is guaranteed and tested over the
full – 40°C to 125°C operating junction temperature range.
Note 3:
The LT3028 is tested and specified for these conditions with the
ADJ1/ADJ2 pin connected to the corresponding OUT1/OUT2 pin.
3028f
3
LT3028
ELECTRICAL CHARACTERISTICS
Note 4:
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 5:
To satisfy requirements for minimum input voltage, the LT3028 is
tested and specified for these conditions with an external resistor divider
(two 250k resistors) for an output voltage of 2.44V. The external resistor
divider will add a 5µA DC load on the output.
Note 6:
Dropout voltage is the minimum input to output voltage differential
needed to maintain regulation at a specified output current. In dropout, the
output voltage will be equal to: V
IN
– V
DROPOUT
.
Note 7:
GND pin current is tested with V
IN
= 2.44V and a current source
load. This means the device is tested while operating in its dropout region
or at the minimum input voltage specification. This is the worst-case GND
pin current. The GND pin current will decrease slightly at higher input
voltages. Total GND pin current is equal to the sum of GND pin currents
from Output 1 and Output 2.
Note 8:
ADJ1 and ADJ2 pin bias current flows into the pin.
Note 9:
SHDN1 and SHDN2 pin current flows into the pin.
Note 10:
For the LT3028 dropout voltage will be limited by the minimum
input voltage specification under some output voltage/load conditions. See
the curve of Minimum Input Voltage in the Typical Performance
Characteristics.
TYPICAL PERFOR A CE CHARACTERISTICS
Output 2
Typical Dropout Voltage
500
450
DROPOUT VOLTAGE (mV)
DROPOUT VOLTAGE (mV)
DROPOUT VOLTAGE (mV)
400
350
300
250
200
150
100
50
0
0
10 20 30 40 50 60 70 80 90 100
OUTPUT CURRENT (mA)
3028 G01
T
J
= 125°C
T
J
= 25°C
Output 1
Typical Dropout Voltage
500
GUARANTEED DROPOUT VOLTAGE (mV)
450
DROPOUT VOLTAGE (mV)
T
J
= 125°C
350
300
250
200
150
100
50
0
0
50 100 150 200 250 300 350 400 450 500
OUTPUT CURRENT (mA)
3028 G04
350
300
250
200
150
100
50
0
0
T
J
≤
125°C
T
J
≤
25°C
DROPOUT VOLTAGE (mV)
400
T
J
= 25°C
4
U W
Output 2
Guaranteed Dropout Voltage
500
450
400
350
300
250
200
150
100
50
0
0
10 20 30 40 50 60 70 80 90 100
OUTPUT CURRENT (mA)
3028 G02
Output 2 Dropout Voltage
500
450
400
350
300
250
200
150
100
50
0
–50 –25
I
L
= 50mA
I
L
= 10mA
I
L
= 1mA
I
L
= 100mA
= TEST POINTS
T
J
≤
125°C
T
J
≤
25°C
50
25
0
75
TEMPERATURE (°C)
100
125
3028 G03
Output 1
Guaranteed Dropout Voltage
500
450
400
Output 1 Dropout Voltage
500
450
400
350
300
250
200
150
100
50
I
L
= 10mA
50
25
0
75
TEMPERATURE (°C)
I
L
= 1mA
I
L
= 50mA
I
L
= 500mA
I
L
= 250mA
I
L
= 100mA
= TEST POINTS
50 100 150 200 250 300 350 400 450 500
OUTPUT CURRENT (mA)
3028 G05
0
–50 –25
100
125
3028 G06
3028f
LT3028
TYPICAL PERFOR A CE CHARACTERISTICS
Quiescent Current (Per Output)
50
45
1.240
1.235
QUIESCENT CURRENT (µA)
QUIESCENT CURRENT (µA)
40
35
30
25
20
15
10
5 V
IN
= 6V
R
L
= 250k, I
L
= 5µA
0
0
25
–50 –25
V
SHDN
= V
IN
ADJ PIN VOLTAGE (V)
50
75
TEMPERATURE (°C)
3028 G07
Output 2 GND Pin Current
2.50
2.25
T
J
= 25°C
*FOR V
OUT
= 1.22V
2.50
2.25
GND PIN CURRENT (mA)
GND PIN CURRENT (mA)
2.00
1.75
1.50
1.25
1.00
0.75
0.50
0.25
0
0
1
2
1.75
1.50
1.25
1.00
0.75
0.50
0.25
0
GND PIN CURRENT (µA)
R
L
= 12.2Ω
I
L
= 100mA*
R
L
= 24.4Ω
I
L
= 50mA*
R
L
= 1.22k
I
L
= 1mA*
R
L
= 122Ω
I
L
= 10mA*
8
9
10
3 4 5 6 7
INPUT VOLTAGE (V)
Output 1 GND Pin Current
12
10
GND PIN CURRENT (mA)
12
8
6
4
2
0
R
L
= 2.44Ω
I
L
= 500mA*
R
L
= 4.07Ω
I
L
= 300mA*
SHDN PIN THRESHOLD (V)
T
J
= 25°C
V
IN
= V
SHDN
*FOR V
OUT
= 1.22V
GND PIN CURRENT (mA)
R
L
= 12.2Ω
I
L
= 100mA*
0
1
2
3 4 5 6 7
INPUT VOLTAGE (V)
U W
100
3028 G10
ADJ1 or ADJ2 Pin Voltage
I
L
= 1mA
40
Quiescent Current (Per Output)
T
J
= 25°C
35 R
L
= 250k
30
25
20
15
10
5
0
V
SHDN
= 0V
0
2
4
6 8 10 12 14 16 18 20
INPUT VOLTAGE (V)
3028 G09
1.230
1.225
1.220
1.215
1.210
1.205
V
SHDN
= V
IN
125
1.200
–50 –25
0
25
50
75
100
125
TEMPERATURE (°C)
3028 G08
Output 2
GND Pin Current vs I
LOAD
V
IN
= V
OUT(NOMINAL)
+ 1V
T
J
= 25°C
1200
1000
800
600
400
200
0
Output 1 GND Pin Current
2.00
R
L
= 24.4Ω
I
L
= 50mA*
T
J
= 25°C
V
IN
= V
SHDN
*FOR V
OUT
= 1.22V
R
L
= 122Ω
I
L
= 10mA*
R
L
= 1.22k
I
L
= 1mA*
0
1
2
3 4 5 6 7
INPUT VOLTAGE (V)
8
9
10
0
10 20 30 40 50 60 70 80 90 100
OUTPUT CURRENT (mA)
3028 G11
3028 G12
Output 1
GND Pin Current vs I
LOAD
V
IN
= V
OUT(NOMINAL)
+ 1V
T
J
= 25°C
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
SHDN1 or SHDN2 Pin Threshold
(On-to-Off)
I
L
= 1mA
10
8
6
4
2
0
8
9
10
0
50 100 150 200 250 300 350 400 450 500
OUTPUT CURRENT (mA)
3028 G14
0
–50 –25
50
25
75
0
TEMPERATURE (°C)
100
125
3028 G13
3028 G15
3028f
5
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