LT1316
Micropower
DC/DC Converter
with Programmable
Peak Current Limit
FEATURES
s
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DESCRIPTION
The LT
®
1316 is a micropower step-up DC/DC converter
that operates from an input voltage as low as 1.5V. A
programmable input current limiting function allows pre-
cise control of peak switch current. Peak switch current
can be set to any value between 30mA and 500mA by
adjusting one resistor. This is particularly useful for
DC/DC converters operating from high source impedance
inputs such as lithium coin cells or telephone lines.
The fixed off-time, variable on-time regulation scheme
results in quiescent current of only 33µA in active mode.
Quiescent current decreases to 3µA in shutdown with the
low-battery detector still active.
The LT1316 is available in 8-lead MSOP and SO packages.
, LTC and LT are registered trademarks of Linear Technology Corporation.
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s
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Precise Control of Peak Switch Current
Quiescent Current:
33µA in Active Mode
3µA in Shutdown Mode
Low-Battery Detector Active in Shutdown
Low Switch V
CESAT
: 300mV at 500mA
8-Lead MSOP and SO Packages
Operates with V
IN
as Low as 1.5V
Logic Level Shutdown Pin
APPLICATIONS
s
s
s
Battery Backup
LCD Bias
Low Power – 48V to 5V/3.3V Converters
TYPICAL APPLICATION
2-Cell to 5V Step-Up Converter
L1
47µH
6
7
V
IN
SHDN
LT1316
NC
2
LBI
R
SET
3
R5
10k
1%
D1: MOTOROLA MBR0520L
L1: SUMIDA CD43-470
LBO
GND
4
1
NC
R2
324k
1%
5
SW
FB
8
D1
R1
1M
1%
5V
50mA
90
3.3V
IN
2.5V
IN
2 CELLS
C1
47µF
C2
47µF
EFFICIENCY (%)
+
+
80
70
60
1316 TA01
0.1
U
U
U
Efficiency vs Load Current
1.8V
IN
1
10
100
1316 TA02
LOAD CURRENT (mA)
1
LT1316
ABSOLUTE
MAXIMUM
RATINGS
V
IN
Voltage .............................................................. 12V
SW Voltage ............................................... – 0.4V to 30V
FB Voltage ..................................................... V
IN
+ 0.3V
R
SET
Voltage ............................................................. 5V
SHDN Voltage ............................................................ 6V
LBI Voltage ................................................................V
IN
LBO Voltage ............................................................. 12V
Maximum Switch Current ................................... 750mA
Maximum Junction Temperature ......................... 125°C
Operating Temperature Range
Commercial ............................................. 0°C to 70°C
Extended Commercial (Note 1) .......... – 40°C to 85°C
Industrial (Note 2) .............................. – 40°C to 85°C
Storage Temperature Range ................. – 65°C to 150°C
Lead Temperature (Soldering, 10 sec).................. 300°C
PACKAGE/ORDER INFORMATION
TOP VIEW
LBO
LBI
R
SET
GND
1
2
3
4
8
7
6
5
FB
SHDN
V
IN
SW
ORDER PART
NUMBER
LT1316CMS8
MS8 PART MARKING
LTCD
ORDER PART
NUMBER
MS8 PACKAGE
8-LEAD PLASTIC MSOP
T
JMAX
= 125°C,
θ
JA
= 160°C/W
TOP VIEW
LBO 1
LBI 2
R
SET
3
GND 4
8
7
6
5
FB
SHDN
V
IN
SW
LT1316CS8
LT1316IS8
S8 PART MARKING
1316
1316I
S8 PACKAGE
8-LEAD PLASTIC SO
T
JMAX
= 125°C,
θ
JA
= 120°C/W
Consult factory for Military grade parts.
ELECTRICAL CHARACTERISTICS
Commercial grade 0°C to 70°C, Industrial grade – 40°C to 85°C, V
IN
= 2V, V
SHDN
= V
IN
, T
A
= 25°C unless otherwise noted. (Notes 1, 2)
PARAMETER
Minimum Operating Voltage
Maximum Operating Voltage
Quiescent Current
Quiescent Current in Shutdown
FB Pin Bias Current
Line Regulation
LBI Input Threshold
LBI Pin Bias Current
LBI Input Hysteresis
LBO Output Voltage Low
LBO Output Leakage Current
SHDN Input Voltage High
SHDN Input Voltage Low
SHDN Pin Bias Current
V
SHDN
= 5V
V
SHDN
= 0V
I
SINK
= 500µA
LBI = 1.7V, LBO = 5V
V
IN
= 1.8V to 12V
Falling Edge
V
SHDN
= 2V, Not Switching
q
CONDITIONS
MIN
TYP
1.5
33
MAX
1.65
12
45
50
5
10
30
0.15
1.25
20
65
0.4
0.1
0.4
UNITS
V
V
µA
µA
µA
µA
nA
%/V
V
nA
mV
V
µA
V
V
µA
µA
V
SHDN
= 0V, V
IN
= 2V
V
SHDN
= 0V, V
IN
= 5V
q
q
q
q
q
q
q
q
q
q
q
q
q
3
7
3
0.04
1.1
1.17
3
35
0.2
0.01
1.4
2
–1
5
–3
2
U
W
U
U
W W
W
LT1316
ELECTRICAL CHARACTERISTICS
Commercial grade 0°C to 70°C, Industrial grade – 40°C to 85°C, V
IN
= 2V, V
SHDN
= V
IN
, T
A
= 25°C unless otherwise noted. (Notes 1, 2)
PARAMETER
Switch OFF Time
CONDITIONS
FB > 1V
q
MIN
1.4
1.1
4.4
3.4
74
73
TYP
2.0
3.4
6.3
76
0.30
0.06
0.1
MAX
2.6
3.0
8.2
9.5
90
90
0.4
0.15
5
UNITS
µs
µs
µs
µs
µs
%
%
V
V
µA
FB < 1V
Switch ON Time
Maximum Duty Cycle
Switch Saturation Voltage
Switch Leakage
Current Limit Not Asserted
1V < FB < 1.2V
Current Limit Not Asserted
1V < FB < 1.2V
I
SW
= 0.5A
I
SW
= 0.1A
Switch Off, V
SW
= 5V
q
q
q
q
q
Commercial grade 0°C to 70°C, V
IN
= 2V, V
SHDN
= V
IN
, T
A
= 25°C unless otherwise noted.
FB Comparator Trip Point
Peak Switch Current
R
SET
= 27.4k, T
A
= 25°C
R
SET
= 27.4k, T
A
=0°C
R
SET
= 27.4k, T
A
= 70°C
R
SET
= 10K
R
SET
= 121k
q
q
1.21
90
90
70
250
1.23
100
100
90
290
25
1.25
110
115
110
340
V
mA
mA
mA
mA
mA
Industrial grade – 40°C to 85°C, V
IN
= 2V, V
SHDN
= V
IN
, T
A
= 25°C unless otherwise noted.
FB Comparator Trip Point
Peak Switch Current
R
SET
= 27.4k,
R
SET
= 10k
q
q
q
1.205
70
200
1.23
100
290
1.255
125
370
V
mA
mA
The
q
denotes specifications which apply over the specified temperature
range.
Note 1:
C grade device specifications are guaranteed over the 0°C to 70°C
temperature range. In addition, C grade device specifications are assured
over the – 40°C to 85°C temperature range by design or correlation, but
are not production tested.
Note 2:
I grade device specifications are guaranteed over the – 40°C to
85°C temperature range.
TYPICAL PERFORMANCE CHARACTERISTICS
Load Transient Response
V
OUT
100mV/DIV
AC COUPLED
50mA
I
LOAD
0mA
1316 G01
U W
Burst Mode
TM
Operation
V
OUT
100mV/DIV
AC COUPLED
V
SW
5V/DIV
INDUCTOR
CURRENT
200mA/DIV
1316 G02
Burst Mode IS A TRADEMARK OF LINEAR TECHNOLOGY
CORPORATION.
3
LT1316
TYPICAL PERFORMANCE CHARACTERISTICS
Switch Saturation Voltage
vs Switch Current
500
SWITCH SATURATION VOLTAGE (mV)
75°C
400
300
–40°C
200
25°C
100
4
OFF-TIME (µs)
–25
0
25
50
TEMPERATURE (°C)
75
100
1316 G04
100°C
LBI PIN CURRENT (nA)
0
0
100 200 300 400 500 600 700 800
SWITCH CURRENT (mA)
1316 G03
Maximum On-Time
vs Temperature
8
36
QUIESCENT CURRENT (µA)
MAXIMUM ON-TIME (µs)
7
32
FEEDBACK VOLTAGE (V)
6
5
–50
–25
0
25
50
TEMPERATURE (°C)
FB Pin Bias Current
vs Temperature
4
SHUTDOWN PIN CURRENT (µA)
4
FB PIN BIAS CURRENT (nA)
3
PEAK SWITCH CURRENT (mA)
3
2
1
–50
–25
0
25
50
TEMPERATURE (°C)
4
U W
75
1316 G06
LBI Pin Bias Current
vs Temperature
8
4
Off-Time vs Temperature
6
3
2
2
1
0
–50
0
–50
–25
0
25
50
TEMPERATURE (°C)
75
100
1316 G05
Quiescent Current vs Temperature
1.240
Feedback Voltage vs Temperature
34
1.235
1.230
30
28
1.225
100
26
–50
–25
0
25
50
TEMPERATURE (°C)
75
100
1316 G07
1.220
–50
–25
0
25
50
TEMPERATURE (°C)
75
100
1316 G08
Shutdown Pin Bias Current
vs Shutdown Pin Voltage
1000
Peak Switch Current
vs Temperature
R
SET
= 4.84k
R
SET
= 10k
2
100
R
SET
= 27.4k
1
R
SET
= 97.3k
0
–1
75
100
1316 G11
0
1
2
3
4
5
SHUTDOWN PIN VOLTAGE (V)
6
1316 G09
10
–50
–25
0
25
50
TEMPERATURE (°C)
75
100
1316 G10
LT1316
PIN FUNCTIONS
LBO (Pin 1):
Low-Battery Detector Output. Open collector
can sink up to 500µA. Low-battery detector remains active
in shutdown mode.
LBI (Pin 2):
Low-Battery Detector Input. When voltage at
this pin drops below 1.17V, LBO goes low.
R
SET
(Pin 3):
A resistor between R
SET
and GND programs
peak switch current. The resistor value should be between
3k and 150k. Do not float or short to ground. This is a high
impedance node. Keep traces at this pin as short as
possible. Do not put capacitance at this pin.
GND (Pin 4):
Ground. Connect directly to ground plane.
SW (Pin 5):
Collector of NPN Power Transistor. Keep
traces at this pin as short as possible.
V
IN
(Pin 6):
Input Supply. Must be bypassed close to the
pin.
SHDN (Pin 7):
Shutdown. Ground this pin to place the part
in shutdown mode (only the low-battery detector remains
active). Tie to a voltage between 1.4V and 6V to enable the
device. SHDN pin is logic level and need only meet the
logic specification (1.4V for high, 0.4V for low).
FB (Pin 8):
Feedback Pin. Reference voltage is 1.23V.
Connect resistive divider tap here. Minimize trace area at
FB. Set V
OUT
according to: V
OUT
= 1.23V(1 + R1/R2).
BLOCK DIAGRA
LB0
1
6
LBI 2
+
A3
–
1.17V
1.5V
UNDERVOLTAGE
LOCKOUT
R3 = 10R4
R4
8
FB
R2
A1
A2
0.5V
+
A4
DRIVER
Q2
×1
Q1
×200
4
R
SET
R5
GND
OSCILLATOR
6.3µs ON
2µs OFF
–
3
7
1316 F01
SHDN
Figure 1. LT1316 Block Diagram
–
+
–
+
W
U
U
U
L1
V
IN
D1
V
OUT
C1
R1
V
IN
5
SW
V
REF
1.23V
5
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