EXPOSED PAD (PIN 9) IS GND, MUST BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH
LTC3873ETS8-5#PBF
LTC3873ITS8-5#PBF
LTC3873EDDB-5#PBF
LTC3873IDDB-5#PBF
LEAD BASED FINISH
LTC3873ETS8-5
LTC3873ITS8-5
LTC3873EDDB-5
LTC3873IDDB-5
TAPE AND REEL
LTC3873ETS8-5#TRPBF
LTC3873ITS8-5#TRPBF
LTC3873EDDB-5#TRPBF
LTC3873IDDB-5#TRPBF
TAPE AND REEL
LTC3873ETS8-5#TR
LTC3873ITS8-5#TR
LTC3873EDDB-5#TR
LTC3873IDDB-5#TR
PART MARKING*
LTCSP
LTCSP
LCSM
LCSM
PART MARKING*
LTCSP
LTCSP
LCSM
LCSM
PACKAGE DESCRIPTION
8-Lead Plastic TSOT-23
8-Lead Plastic TSOT-23
8-Lead (3mm
×
2mm) Plastic DFN
8-Lead (3mm
×
2mm) Plastic DFN
PACKAGE DESCRIPTION
8-Lead Plastic TSOT-23
8-Lead Plastic TSOT-23
8-Lead (3mm
×
2mm) Plastic DFN
8-Lead (3mm
×
2mm) Plastic DFN
TEMPERATURE RANGE
–40°C to 85°C
–40°C to 125°C
–40°C to 85°C
–40°C to 125°C
TEMPERATURE RANGE
–40°C to 85°C
–40°C to 125°C
–40°C to 85°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/
38735fb
2
LTC3873-5
ELECTRICAL CHARACTERISTICS
PARAMETER
Input DC Supply Current
Normal Operation
Shutdown
UVLO
Undervoltage Lockout Threshold
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
CC
= 5V unless otherwise noted. (Note 2)
CONDITIONS
Typicals at V
CC
= 5V (Note 4)
V
ITH
= 1.9V
V
RUN/SS
= 0V
V
CC
= UVLO Threshold – 100mV, V
RUN/SS
= V
CC
V
CC
Rising
V
CC
Falling
V
CC
Hysteresis
V
RUN/SS
Falling
V
RUN/SS
Rising
(Note 5)
3.5V < V
CC
< 9V (Note 5)
V
ITH
= 1.6V (Note 5)
V
ITH
= 1V (Note 5)
(Note 5)
V
RUN/SS
= 0V
V
RUN/SS
= 1.3V
1.5
5
70
160
C
LOAD
= 3000pF (Note 6)
C
LOAD
= 3000pF (Note 6)
IPRG = GND
IPRG = Float
IPRG = V
IN
I
IN
= 1mA, I
IN
= 25mA, V
RUN/SS
= 0V
l
l
l
l
l
l
l
l
l
MIN
TYP
300
50
35
MAX
400
80
50
4.4
3.3
1.7
0.9
1.0
1.218
UNITS
μA
μA
μA
V
V
V
V
V
V
mV/V
%
%
3.8
2.5
0.9
0.5
0.6
1.182
4.1
2.9
1.25
0.7
0.8
1.2
0.1
0.05
–0.05
25
3
15
78
20
200
40
40
Shutdown Threshold (at RUN/SS)
Regulated Feedback Voltage
Feedback Voltage Line Regulation
Feedback Voltage Load Regulation
V
FB
Input Current
RUN/SS Pull Up Current
Maximum Duty Cycle
I
SLMAX
, Peak Slope Compensation Current
Oscillator Frequency
Gate Drive Rise Time
Gate Drive Fall Time
Peak Current Sense Voltage
50
4.5
25
84
240
nA
μA
μA
%
μA
kHz
ns
ns
95
165
265
9
110
185
295
9.3
3.3
125
210
325
9.6
mV
mV
mV
V
ms
V
IN
Shunt Regulator Voltage
Default Internal Soft-Start
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 LTC3873E-5 is guaranteed to meet performance specifications
from 0°C to 85°C. Specifications over the –40°C to 85°C operating
temperature range are assured by design, characterization and correlation
with statistical process controls. The LTC3873I-5 is guaranteed to meet
performance specifications over the full –40°C to 125°C operating
temperature range.
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
•
θ
JA
)
Note 4:
The dynamic input supply current is higher due to power MOSFET
gate charging (Q
G
• f
OSC
). See Applications Information.
Note 5:
The LTC3873-5 is tested in a feedback loop which servos V
FB
to
the reference voltage with the I
TH
pin forced to the midpoint of its voltage
range (0.7V ≤ V
ITH
≤ 1.9V, midpoint = 1.3V).
Note 6:
Rise and fall times are measured at 10% and 90% levels.
V
CC
= 5.6V.
38735fb
3
LTC3873-5
TYPICAL PERFORMANCE CHARACTERISTICS
Regulated Feedback Voltage vs
Temperature
1.25
1.24
1.23
1.22
1.21
1.20
1.19
1.18
–60 –40 –20
1.2025
1.2020
2.0
1.2015
V
FB
VOLTAGE (V)
I
TH
VOLTAGE (V)
1.2010
1.2005
1.2000
0.5
1.1995
1.1990
3
4
5
7
6
V
IN
(V)
8
9
0
1.5
V
FB
VOLTAGE (V)
Regulated Feedback Voltage Line
Regulation
2.5
I
TH
Voltage vs RUN/SS Voltage
V
IN
= 5V
1.0
40 60 80 100 120
TEMPERATURE (°C)
38735 G01
0
20
10
0
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
RUN/SS VOLTAGE (V)
38735 G03
38735 G02
Shutdown Mode I
Q
vs V
IN
70
65
SHUTDOWN MODE I
Q
(μA)
SHUTDOWN MODE I
Q
(μA)
60
55
50
45
40
35
30
25
20
3
4
5
7
6
V
IN
(V)
8
9
10
80
70
60
Shutdown I
Q
vs Temperature
100
90
80
70
TIME (ns)
60
50
40
30
20
10
0
–60 –40 –20 0 20 40 60 80 100 120
TEMPERATURE (°C)
3873-5 G05
Gate Drive Rise and Fall Time
vs C
LOAD
50
40
30
RISE TIME
FALL TIME
20
10
0
0
2000
6000
4000
C
LOAD
(pF)
8000
10000
38735 G06
3873-5 G04
RUN Threshold vs Temperature
1.0
10.2
10.1
REGULATION VOLTAGE (V)
0.9
RUN THRESHOLDS (V)
0.8
RISING
10.0
9.9
9.8
9.7
9.6
9.5
9.4
9.3
0.5
–60 –40 –20 0 20 40 60 80 100 120
TEMPERATURE (°C)
38735 G07
Shunt Regulator Voltage
vs I
SHUNT
0.7
FALLING
0.6
9.2
0
5
10
15
20 25 30
I
SHUNT
(mA)
35
40
45
3873-5 G08
38735fb
4
LTC3873-5
TYPICAL PERFORMANCE CHARACTERISTICS
Frequency vs Temperature
250
300
V
IN
= 5V
MAXIMUM SENSE THRESHOLD (mV)
250
200
150
IPRG = GND
100
50
0
–60 –40 –20 0 20 40 60 80 100 120
TEMPERATURE (°C)
38735 G10
Maximum Sense Threshold
vs Temperature
IPRG = V
IN
230
FREQUECY (kHz)
IPRG = FLOAT
210
190
170
150
–60 –40 –20 0 20 40 60 80 100 120
TEMPERATURE (°C)
3873-5 G09
PIN FUNCTIONS
(TS8/DD8)
IPRG (Pin 1/Pin 4):
Current Sense Limit Select Pin.
I
TH
(Pin 2/Pin 3):
This pin serves as the error amplifier
compensation point. Nominal voltage range for this pin
is 0.7V to 1.9V.
V
FB
(Pin 3/Pin 2):
This pin receives the feedback voltage
from an external resistor divider across the output.
GND (Pin 4/Pin 1):
Ground Pin.
NGATE (Pin 5/Pin 8):
Gate Drive for the External N-Channel
MOSFET. This pin swings from 0V to V
IN
.
V
CC
(Pin 6/Pin 7):
Supply Pin. This pin must be closely
decoupled to GND (Pin 4).
RUN/SS (Pin 7/Pin 6):
Shutdown and External Soft-Start
Pin. In shutdown, all functions are disabled and the NGATE
pin is held low.
SW (Pin 8/Pin 5):
Switch node connection to inductor and
current sense input pin through external slope compensa-
tion resistor. Normally, the external N-channel MOSFET’s
drain is connected to this pin.
Exposed Pad (NA/Pin 9):
Ground. Must be soldered to PCB
for electrical contact and rated thermal performance.
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