LT1317IS8#TRPBF [Linear]
LT1317 - Micropower, 600kHz PWM DC/DC Converters; Package: SO; Pins: 8; Temperature Range: -40°C to 85°C;
| 型号： | LT1317IS8#TRPBF |
| 厂家： | 
Linear |
| 描述： | LT1317 - Micropower, 600kHz PWM DC/DC Converters; Package: SO; Pins: 8; Temperature Range: -40°C to 85°C 开关 光电二极管 |
| 文件： | 总16页 (文件大小：399K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
LT1317/LT1317B
Micropower, 600kHz PWM
DC/DC Converters
U
DESCRIPTION
FEATURES
The LT®1317/LT1317B are micropower, fixed frequency
step-up DC/DC converters that operate over a wide input
voltage range of 1.5V to 12V. The LT1317 features auto-
matic shifting to power saving Burst ModeTM operation at
light loads. High efficiency is maintained over a broad
300µA to 200mA load range. Peak switch current during
Burst Mode operation is kept below 250mA for most
operating conditions which results in low output ripple
voltage, even at high input voltages. The LT1317B does
notshiftintoBurstModeoperationatlightloads, eliminat-
ing lowfrequency output rippleatthe expenseof light load
efficiency.
■
100µA Quiescent Current
■
Operates with VIN as Low as 1.5V
■
600kHz Fixed Frequency Operation
Starts into Full Load
■
■
Low-Battery Detector Active in Shutdown
■
Automatic Burst Mode Operation at
Light Load (LT1317)
■
Continuous Switching at Light Loads (LT1317B)
■
Low VCESAT Switch: 300mV at 500mA
■
Pin for Pin Compatible with the LT1307/LT1307B
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APPLICATIONS
The LT1317/LT1317B contain an internal low-battery de-
tector with a 200mV reference that stays alive when the
device goes into shutdown.
■
Cellular Telephones
■
Cordless Telephones
■
Pagers
No-load quiescent current of the LT1317 is 100µA and
shuts down to 30µA. The internal NPN power switch
handles a 500mA current with a voltage drop of just
300mV.
■
GPS Receivers
■
Battery Backup
■
Portable Electronic Equipment
■
Glucose Meters
■
Diagnostic Medical Instrumentation
The LT1317/LT1317B are available in MS8 and SO-8
packages.
, LTC and LT are registered trademarks of Linear Technology Corporation.
Burst Mode is a trademark of Linear Technology Corporation.
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TYPICAL APPLICATION
2-Cell to 3.3V Converter Efficiency
L1
10µH
D1
90
2.2V
3V
IN
IN
+
C1
V
LBI
SW
FB
80
70
60
50
40
IN
47µF
3.3V
1.65V
IN
200mA
LT1317
R1
1M
1%
2
SHUTDOWN
SHDN
V
C
LBO
GND
CELLS
+
C2
47µF
R2*
604k
1%
R
C
33k
C
C
3.3nF
D1: MBR0520
L1: SUMIDA CD43-100
* FOR 5V OUTPUT, R2 = 332k, 1%
1317 F01
0.3
1
10
100
1000
LOAD CURRENT (mA)
Figure 1. 2-Cell to 3.3V Boost Converter
1317 TA01
1
LT1317/LT1317B
W W W
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ABSOLUTE AXI U RATI GS (Note 1)
Junction Temperature.......................................... 125°C
VIN, LBO Voltage..................................................... 12V
SW Voltage ............................................... –0.4V to 30V
FB Voltage .................................................... VIN + 0.3V
VC Voltage ................................................................ 2V
LBI Voltage ............................................ 0V ≤ VLBI ≤ 1V
SHDN Voltage ............................................................ 6V
Operating Temperature Range
Commercial ........................................... 0°C to 70°C
Industrial ............................................ –40°C to 85°C
Storage Temperature Range ................ –65°C to 150°C
Lead Temperature (Soldering, 10 sec)................ 300°C
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/O
PACKAGE RDER I FOR ATIO
ORDER PART
ORDER PART
TOP VIEW
NUMBER
NUMBER
TOP VIEW
V
1
2
3
4
8
7
6
5
LBO
LBI
C
V
1
2
3
4
8 LBO
7 LBI
C
LT1317CMS8
LT1317BCMS8
LT1317CS8
LT1317BCS8
LT1317IS8
LT1317BIS8
FB
SHDN
GND
FB
SHDN
GND
6 V
IN
V
IN
5 SW
SW
MS8 PACKAGE
8-LEAD PLASTIC MSOP
S8 PACKAGE
8-LEAD PLASTIC SO
TJMAX = 125°C, θJA = 160°C/W
MS8 PART MARKING
S8 PART MARKING
TJMAX = 125°C, θJA = 120°C/W
1317
LTHA
LTHB
1317B
1317I
1317BI
Consult factory for Military grade parts.
ELECTRICAL CHARACTERISTICS
Commercial Grade VIN = 2V, VSHDN = 2V, TA = 25°C, unless otherwise noted.
SYMBOL PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
I
Quiescent Current
Not Switching, V
= 2V (LT1317)
●
●
100
25
4.8
160
40
6.5
7.5
µA
µA
mA
mA
Q
SHDN
V
V
V
= 0V (LT1317/LT1317B)
= 2V, Switching (LT1317B)
= 2V, Switching (LT1317B)
SHDN
SHDN
SHDN
●
V
Feedback Voltage
1.22
1.20
1.24
1.24
1.26
1.26
V
V
FB
●
●
●
●
I
FB Pin Bias Current (Note 2)
Input Voltage Range
12
60
12
nA
V
B
1.5
70
g
Error Amp Transconductance
Error Amp Voltage Gain
Maximum Duty Cycle
∆I = 5µA
140
700
85
240
µmhos
V/V
m
A
V
●
●
80
%
Switch Current Limit (Note 3)
V
V
= 2.5V, Duty Cycle = 30%
= 2.5V, Duty Cycle = 30%
710
660
800
1300
1350
mA
mA
IN
IN
Burst Mode Operation Switch Current Limit
Switching Frequency
Duty Cycle = 30% (LT1317)
275
620
mA
kHz
f
●
520
720
OSC
2
LT1317/LT1317B
ELECTRICAL CHARACTERISTICS
Commercial Grade VIN = 2V, VSHDN = 2V, TA = 25°C unless otherwise noted.
SYMBOL PARAMETER
Shutdown Pin Current
CONDITIONS
MIN
TYP
MAX
UNITS
V
V
= V
= 0V
●
●
0.015
–2.3
0.06
–6
µA
µA
SHDN
SHDN
IN
LBI Threshold Voltage
190
180
200
200
210
220
mV
mV
●
●
●
●
LBO Output Low
I
= 10µA
0.15
0.02
5
0.25
0.1
40
V
µA
SINK
LBO Leakage Current
V
V
= 250mV, V
= 5V
LBO
LBI
LBI
LBI Input Bias Current (Note 4)
Low-Battery Detector Gain
Switch Leakage Current
= 150mV
nA
1MΩ Load
2000
0.01
300
V/V
µA
V
= 5V
●
3
SW
Switch V Sat
I
= 500mA
SW
350
400
mV
mV
CE
●
●
●
●
Reference Line Regulation
SHDN Input Voltage High
SHDN Input Voltage Low
1.8V ≤ V ≤ 12V
0.08
0.15
6
%/V
V
IN
1.4
0.4
V
Industrial Grade VIN = 2V, VSHDN = 2V, –40°C ≤ TA ≤ 85°C unless otherwise noted.
SYMBOL PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
I
Quiescent Current
Not Switching, V
= 2V (LT1317)
●
●
●
160
40
7.5
µA
µA
mA
Q
SHDN
V
SHDN
V
SHDN
= 0V (LT1317/LT1317B)
= 2V, Switching (LT1317B)
V
Feedback Voltage
●
●
●
●
●
●
●
1.20
1.26
80
V
nA
FB
I
FB Pin Bias Current (Note 2)
Input Voltage Range
B
1.7
70
12
V
g
m
Error Amp Transconductance
Maximum Duty Cycle
∆I = 5µA
140
240
µmhos
%
80
Switch Current Limit (Note 3)
Switching Frequency
V
IN
= 2.5V, Duty Cycle = 30%
550
500
1350
750
mA
f
kHz
OSC
Shutdown Pin Current
V
SHDN
V
SHDN
= V
= 0V
●
●
0.1
–7
µA
µA
IN
LBI Threshold Voltage
LBO Output Low
●
●
●
●
●
●
●
●
●
180
220
0.25
0.1
60
mV
V
I
= 10µA
= 250mV, V
= 150mV
= 5V
SINK
LBO Leakage Current
LBI Input Bias Current (Note 4)
Switch Leakage Current
V
V
V
= 5V
LBO
µA
nA
µA
mV
%/V
V
LBI
LBI
SW
SW
3
Switch V Sat
I
= 500mA
400
0.15
6
CE
Reference Line Regulation
SHDN Input Voltage High
SHDN Input Voltage Low
1.8V ≤ V ≤ 12V
IN
1.4
0.4
V
The
●
denotes specifications which apply over the full operating
Note 2: Bias current flows into FB pin.
temperature range.
Note 3: Switch current limit guaranteed by design and/or correlation to
Note 1: Absolute Maximum Ratings are those values beyond which the life
static tests. Duty cycle affects current limit due to ramp generator.
of a device may be impaired.
Note 4: Bias current flows out of LBI pin.
3
LT1317/LT1317B
TYPICAL PERFOR A CE CHARACTERISTICS
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Switch Current Limit,
Duty Cycle = 30%
Oscillator Frequency
Burst Mode Current Limit (LT1317)
1000
900
800
700
600
500
700
650
600
550
500
800
600
400
200
0
V
= 2V
IN
L = 10µH
–40°C
85°C
25°C
–50
–25
0
25
50
75
100
0
2
4
6
8
10
12
0
20
40
60
80
100
TEMPERATURE (°C)
INPUT VOLTAGE
DUTY CYCLE (%)
1317 TPC03
1317 TPC01
1317 TPC02
Switch Current Limit
LBI Input Bias Current
Switch Voltage Drop (VCESAT)
700
600
500
400
300
200
100
0
1200
1000
800
6
5
4
3
2
1
0
85°C
TYPICAL
25°C
–40°C
600
MINIMUM (25°C)
400
200
0
20
40
60
80
100
0
0.2
0.4
0.6
0.8
1
–50
–25
0
25
50
75
100
DUTY CYCLE (%)
SWITCH CURRENT (A)
TEMPERATURE (°C)
1317 TPC04
1317 TPC06
1317 TPC05
Feedback Voltage
LBI Reference Voltage
Quiescent Current, SHDN = 2V
1.25
1.24
1.23
1.22
1.21
1.20
110
100
90
203
202
201
200
199
198
197
196
195
80
70
60
50
40
30
–50
–50
–25
0
25
50
75
100
–25
0
25
50
75
100
–50
–25
0
25
50
75
100
TEMPERATURE (°C)
TEMPERATURE (°C)
TEMPERATURE (°C)
1317 TPC07
1317 TPC09
1317 TPC08
4
LT1317/LT1317B
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TYPICAL PERFOR A CE CHARACTERISTICS
SHDN Pin Current
Quiescent Current, SHDN = 0V
FB Pin Bias Current
26
25
24
23
22
21
20
40
36
32
28
24
20
16
12
8
2
1
0
–1
–2
–3
4
0
–50
–25
0
25
50
75
100
1
2
4
0
5
6
3
–50
–25
0
25
50
75
100
TEMPERATURE (°C)
TEMPERATURE (°C)
SHDN PIN VOLTAGE (V)
1317 TPC10
1317 TPC12
1317 TPC11
2-Cell to 3.3V Converter
Efficiency (LT1317B)
2-Cell to 5V Converter Efficiency
(LT1317B)
5V Output Efficiency, Circuit of
Figure 1 (LT1317)
90
80
70
60
50
90
80
70
60
50
40
90
80
70
60
50
40
V
IN
V
IN
V
IN
= 1.65V
= 2.2V
= 3V
V
= 1.65V
= 2.2V
= 3V
V
V
V
= 1.65V
= 2.2V
= 3V
IN
IN
IN
IN
IN
IN
V
V
0.3
1
10
100
1000
1
10
LOAD CURRENT (mA)
100
1000
1
10
100
1000
LOAD CURRENT (mA)
LOAD CURRENT (mA)
1317 TPC14
1317 TPC15
1317 TPC13
Transient Response (LT1317)
Transient Response (LT1317B)
Burst Mode Operation (LT1317)
VOUT
100mV/DIV
VOUT
100mV/DIV
VOUT
50mV/DIV
AC COUPLED
AC COUPLED
AC COUPLED
IL
IL
IL
200mA/DIV
200mA/DIV
200mA/DIV
VSW
5V/DIV
165mA
ILOAD
165mA
ILOAD
5mA
5mA
V
IN = 2V
VOUT = 3.3V
CIRCUIT OF FIGURE 1
1ms/DIV
1317 TPC16
V
IN = 2V
1ms/DIV
1317 TPC17
V
IN = 2V
20µs/DIV
1317 TPC18
VOUT = 3.3V
CIRCUIT OF FIGURE 1
WITH LT1317B
VOUT = 3.3V
ILOAD = 30mA
CIRCUIT OF FIGURE 1
5
LT1317/LT1317B
TYPICAL PERFOR A CE CHARACTERISTICS
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Load Regulation (LT1317)
Load Regulation (LT1317)
Load Regulation (LT1317)
VOUT
50mV/DIV
DC COUPLED
OFFSET
VOUT
50mV/DIV
DC COUPLED
OFFSET
VOUT
50mV/DIV
DC COUPLED
OFFSET
ADDED
ADDED
ADDED
VIN = 1.5V
VOUT = 5V
ILOAD 25mA/DIV
1317 TPC19
VIN = 2V
VOUT = 5V
ILOAD 25mA/DIV
1317 TPC20
VIN = 2.5V
VOUT = 5V
ILOAD 50mA/DIV
1317 TPC21
Load Regulation (LT1317)
Load Regulation (LT1317)
Load Regulation (LT1317)
VOUT
50mV/DIV
DC COUPLED
OFFSET
VOUT
50mV/DIV
DC COUPLED
OFFSET
VOUT
50mV/DIV
DC COUPLED
OFFSET
ADDED
ADDED
ADDED
VIN = 1.5V
ILOAD 25mA/DIV
1317 TPC22
VIN = 2V
ILOAD 50mA/DIV
1317 TPC23
VIN = 2.5V
ILOAD 50mA/DIV
1317 TPC24
VOUT = 3.3V
VOUT = 3.3V
VOUT = 3.3V
Note: For load regulation pictures, double lines are due to
output capacitor ESR.
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PIN FUNCTIONS
VC (Pin 1): Compensation Pin for Error Amplifier. Con-
nect a series RC network from this pin to ground. Typical
values for compensation are a 33k/3.3nF combination. A
100pFcapacitorfromtheVC pintogroundisoptionaland
improves noise immunity. Minimize trace area at VC.
GND (Pin 4): Ground. Connect directly to local ground
plane.
SW (Pin 5): Switch Pin. Connect inductor/diode here.
Minimize trace area at this pin to keep EMI down.
VIN (Pin 6): Supply Pin. Must be bypassed close to the
pin.
FB (Pin 2): Feedback Pin. Reference voltage is 1.24V.
Connect resistor divider tap here. Minimize trace area at
FB. Set VOUT according to: VOUT = 1.24V(1 + R1/R2).
LBI (Pin 7): Low-Battery Detector Input. 200mV refer-
ence. Voltage on LBI must stay between ground and
700mV. Low-battery detector remains active in shutdown
mode.
SHDN (Pin 3): Shutdown. Pull this pin low for shutdown
mode (only the low-battery detector remains active).
Leavethispinfloatingortietoavoltagebetween1.4Vand
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).
LBO (Pin 8): Low-Battery Detector Output. Open collec-
tor, can sink 10µA. A 1MΩ pull-up is recommended.
6
LT1317/LT1317B
W
BLOCK DIAGRAM
LBI
7
1.24V
+
–
+
–
V
LBO
8
C
REFERENCE
g
1
m
FB
2
A4
200mV
ENABLE
ERROR
AMPLIFIER
+
–
SHDN
V
OUT
SHUTDOWN
3
BIAS
A1
COMPARATOR
R1
(EXTERNAL)
SW
5
FB
R2
–
+
FF
S
(EXTERNAL)
DRIVER
RAMP
GENERATOR
Q3
R
Q
+
Σ
A2
COMPARATOR
+
+
–
A = 2
0.08Ω
600kHz
OSCILLATOR
4
GND 1317 BD
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APPLICATIONS INFORMATION
OPERATION
Iftheoutputloadincreasessufficiently,A1’soutputremains
high, resulting in continuous operation. When the LT1317
is running continuously, peak switch current is controlled
by VC to regulate the output voltage. The switch is turned
on at the beginning of each switch cycle. When the sum-
mation of a signal representing switch current and a ramp
generator(introducedtoavoidsubharmonicoscillationsat
duty factors greater than 50%) exceeds the VC signal,
comparator A2 changes state, resetting the flip-flop and
turning off the switch. Output voltage increases as switch
current is increased. The output, attenuated by a resistor
divider, appears at the FB pin, closing the overall loop.
Frequency compensation is provided by an external series
RC network and an optional capacitor connected between
the VC pin and ground.
The LT1317 combines a current mode, fixed frequency
PWMarchitecturewithBurstModemicropoweroperation
to maintain high efficiency at light loads. Operation can
best be understood by referring to the Block Diagram.
The error amplifier compares voltage at the FB pin with the
internal 1.24V bandgap reference and generates an error
signal VC. When VC decreases below the bias voltage on
hysteretic comparator A1, A1’s output goes low, turning
off all circuitry except the 1.24V reference, error amplifier
and low-battery detector. Total current consumption in
this state is 100µA. As output loading causes the FB
voltage to decrease, VC increases causing A1’s output to
go high, in turn enabling the rest of the IC. Switch current
is limited to approximately 250mA initially after A1’s
output goes high. If the load is light, the output voltage
(and FB voltage) will increase until A1’s output goes low,
turning off the rest of the LT1317. Low frequency ripple
voltage appears at the output. The ripple frequency is
dependent on load current and output capacitance. This
Burst Mode operation keeps the output regulated and
reduces average current into the IC, resulting in high
efficiency even at load currents of 300µA or less.
Low-batterydetectorA4’sopencollectoroutput(LBO)pulls
low when the LBI pin voltage drops below 200mV. There
isnohysteresisinA4, allowingittobeusedasanamplifier
in some applications. The low-battery detector remains
active in shutdown. To enable the converter, SHDN must
be left floating or tied to a voltage between 1.4V and 6V.
7
LT1317/LT1317B
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APPLICATIONS INFORMATION
GROUND PLANE
TheLT1317BdiffersfromtheLT1317inthatthebiaspoint
on A1 is set lower than on the LT1317 so that minimum
switch current can drop below 50mA. Because A1’s bias
point is set lower, there is no Burst Mode operation at light
loads and the device continues switching at constant
frequency. This results in the absence of low frequency
outputvoltagerippleattheexpenseoflightloadefficiency.
1
8
7
6
5
LT1317
2
3
4
V
IN
L
D
C
IN
MULTIPLE
VIAs
The difference between the two devices is clearly illus-
trated in Figure 2. The top two traces in Figure 2 show an
LT1317/LT1317Bcircuit, usingthecomponentsindicated
in Figure 1, set to a 3.3V output. Input voltage is 2V. Load
current is stepped from 2mA to 200mA for both circuits.
Low frequency Burst Mode operation voltage ripple is
observed on Trace A, while none is observed on Trace B.
C
OUT
GND
V
1317 F03
OUT
Figure 3. Recommended Component Placement. Traces Carrying
High Current Are Direct. Trace Area at FB Pin and VC Pin is Kept
Low. Lead Length to Battery Should be Kept Short.
COMPONENT SELECTION
Inductors
LT1317
VOUT
TRACE A
100mV/DIV
AC COUPLED
LT1317B
VOUT
TRACE B
Inductors appropriate for use with the LT1317 must
possess three attributes. First, they must have low core
loss at 600kHz. Most ferrite core units have acceptable
losses at this switching frequency. Inexpensive iron pow-
der cores should be viewed suspiciously, as core losses
can cause significant efficiency penalties at 600kHz. Sec-
ond, the inductor must be able to handle peak switch
current of the LT1317 without saturating. This places a
lower limit on the physical size of the unit. Molded chokes
or chip inductors usually do not have enough core to
supporttheLT1317maximumpeakswitchcurrentandare
unsuitable for the application. Lastly, the inductor should
have low DCR (copper wire resistance) to prevent effi-
ciency-killing I2R losses. Linear Technology has identified
several inductors suitable for use with the LT1317. This is
not an exclusive list. There are many magnetics vendors
whose components are suitable for use. A few vendor’s
components are listed in Table 1.
100mV/DIV
AC COUPLED
200mA
2mA
ILOAD
1ms/DIV
1317 F02
Figure 2. LT1317 Exhibits Ripple at 2mA Load
During Burst Mode Operation, the LT1317B Does Not
LAYOUT HINTS
The LT1317 switches current at high speed, mandating
careful attention to layout for proper performance. You
will not get advertised performance with careless layouts.
Figure 3 shows recommended component placement.
Follow this closely in your PC layout. Note the direct path
of the switching loops. Input capacitor CIN must be placed
close (<5mm) to the IC package. As little as 10mm of wire
or PC trace from CIN to VIN will cause problems such as
inability to regulate or oscillation.
8
LT1317/LT1317B
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APPLICATIONS INFORMATION
Table 1. Inductors Suitable for Use with the LT1317
tobeadjustedtoensureastablesystemfortheentireinput
voltage range. Figure 4 shows a 2V to 3.3V converter with
new values for RC and CC. Figure 5 details transient
response for this circuit. Also, ceramic caps are prone to
temperature effects and the designer must check loop
stabilityovertheoperatingtemperaturerange(seesection
on Frequency Compensation).
MAX
VALUE DCR
HEIGHT
(mm)
PART
MFR
COMMENT
LQH3C100
10µH
0.57 Murata-Erie
2.0
Smallest Size,
Limited Current
Handling
DO1608-103 10µH
0.16
0.18
0.10
Coilcraft
Sumida
Sumida
3.0
3.2
4.5
2.2
CD43-100
CD54-100
10µH
10µH
Input bypass capacitor ESR is less critical and smaller
units may be used. If the input voltage source is physically
near the VIN pin (<5mm), a 10µF ceramic or a 10µF A case
tantalum is adequate.
Best Efficiency
1210 Footprint
CTX32CT-100 10µH
0.50 Coiltronics
Capacitor Selection
Diodes
LowESR(EquivalentSeriesResistance)capacitorsshould
be used at the output of the LT1317. For most applications
a solid tantalum in a C or D case size works well. Accept-
able capacitance values range from 10µF to 330µF with
ESR falling between 0.1Ω and 0.5Ω. If component size is
an issue, tantalum capacitors in smaller case sizes can be
usedbuttheyhavehighESRandoutputvoltageripplemay
reach unacceptable levels.
Most of the application circuits on this data sheet specify
the Motorola MBR0520L surface mount Schottky diode.
In lower current applications, a 1N4148 can be used,
although efficiency will suffer due to the higher forward
drop. This effect is particularly noticeable at low output
voltages. For higher voltage output applications, such as
LCD bias generators, the extra drop is a small percentage
of the output voltage so the efficiency penalty is small. The
low cost of the 1N4148 makes it attractive wherever it can
be used. In through hole applications the 1N5818 is the all
around best choice.
Ceramic capacitors are an alternative because of their
combination of small size and low ESR. A 10µF ceramic
capacitor will work for some applications but the ex-
tremely low ESR of these capacitors may cause loop
stability problems. Compensation components will need
L1
10µH
D1
V
V
IN
OUT
2V
3.3V
V
SW
FB
IN
LT1317B
R1
1M
1%
VOUT
200mV/DIV
AC COUPLED
SHDN
V
C
C1
10µF
GND
C2
10µF
CERAMIC
R2
604k
1%
R
C
20k
C
ILOAD
5mA TO
200mA
C
1500pF
D1: MBR0520
1317 F04
L1: SUMIDA CD43-100
200µs/DIV
1317 F05
Figure 5. Transient Response for the Circuit of Figure 4.
Figure 4. 2V to 3.3V Converter with a 10µF Ceramic Output
Capacitor. RC and CC Have Been Adjusted to Give Optimum
Transient Response.
9
LT1317/LT1317B
U
W U U
APPLICATIONS INFORMATION
MBR0520L
10µH
FREQUENCY COMPENSATION
V
V
OUT
IN
2V
3.3V
The LT1317 has an external compensation pin (VC) which
allows the frequency response to be optimized for the
circuit configuration. In most cases, the values used in
Figure 1 will work. Some circuits may need additional
compensation and a simple trial and error method for
determining the necessary component values is given.
V
SW
IN
1M
15Ω
2W
LT1317
+
+
FB
SHDN
47µF
47µF
V
GND
C
604k
R
C
C2
50Ω
100pF
C
Figure 6 shows the test setup. A load step is applied and
the resulting output voltage waveform is observed. Fig-
ures 7 through 10 detail the response for various values of
R and C in the compensation network. The circuit of
Figure 7 starts with a large C and small R giving a highly
overdampedsystem.Thissystemwillalwaysbestablebut
the output voltage displays a long settling time of >5ms.
Figure 8’s circuit has reduced C giving a shorter settling
time but still overdamped. Figure 9 shows the results
when C is reduced to the point where the system becomes
underdamped. The output voltage responds quickly
(≈200µs to 300µs) but some ringing exists. Figure 10 has
1317 F06
Figure 6. Frequency Response Test Setup
optimum R and C values giving the best possible settling
time with adequate phase margin.
An additional 100pF capacitor (CC2) is connected to the VC
pinandisnecessaryiftheLT1317isoperatednearcurrent
limit. Also, CC2 should be present when higher ESR output
capacitors are used.
VOUT
100mV/DIV
VOUT
100mV/DIV
AC COUPLED
AC COUPLED
ILOAD
ILOAD
2mA TO
200mA
2mA TO
200mA
5ms/DIV
1317 F07
5ms/DIV
1317 F08
Figure 7. With C = 56nF and R = 33k,
the System is Highly Overdamped.
Figure 8. Reducing C to 22nF
Speeds Up the Response. (R = 33k)
VOUT
100mV/DIV
VOUT
100mV/DIV
AC COUPLED
AC COUPLED
ILOAD
ILOAD
2mA TO
200mA
2mA TO
200mA
1ms/DIV
1317 F09
1ms/DIV
1317 F10
Figure 9. Using 680pF for C Results in an
Underdamped System with Ringing. (R = 33k)
Figure 10. 3.3nF and 33k Gives the
Shortest Settling Time with No Ringing.
10
LT1317/LT1317B
U
W U U
APPLICATIONS INFORMATION
LOW-BATTERY DETECTOR
Figure 11 details hookup. R1 and R2 need only be low
enough in value so that the bias current of the LBI pin
doesn’t cause large errors. For R2, 100k is adequate. The
200mV reference can also be accessed as shown in
Figure 12. The low-battery detector remains active in
shutdown.
The LT1317’s low-battery detector is a simple PNP input
gain stage with an open collector NPN output. The nega-
tive input of the gain stage is tied internally to a 200mV
±5% reference. The positive input is the LBI pin. Arrange-
ment as a low-battery detector is straightforward.
3.3V
R1
V
IN
LT1317
LBO
1M
LBI
+
–
TO PROCESSOR
R2
100k
200k
V
IN
200mV
V
LB
– 200mV
2µA
2N3906
REF
LBO
LBI
R1 =
INTERNAL
LT1317
REFERENCE
GND
V
200mV
+
GND
1317 F11
10k
10µF
1317 F12
Figure 11. Setting Low-Battery Detector Trip Point
Figure 12. Accessing 200mV Reference
U
TYPICAL APPLICATIO S
Single Li-Ion Cell to 3.3V SEPIC Converter
3.3V SEPIC Efficiency
C3
1µF
80
MBR0520
L1A*
75
70
65
60
+
C1
47µF
V
SW
FB
IN
V
OUT
LT1317
3.3V
1M
1%
SINGLE
Li-ION
CELL
(2.7V TO
4.2V)
250mA
SHDN
V
L1B*
GND
C
+
C2
47µF
V
V
V
= 2.7V
= 3.5V
= 4.2V
IN
IN
IN
604k
1%
33k
3300pF
55
50
C1, C2: AVX TPSC476M010
C3: AVX 1206YC106KAT
* COILTRONICS CTX20-1
1
10
100
1000
1317 TA03
LOAD CURRENT (mA)
1317 TA03a
11
LT1317/LT1317B
U
TYPICAL APPLICATIO S
5V to 12V Boost Converter
5V to 12V Boost Converter Efficiency
L1
22µH
90
MBR0520
V
IN
5V
V
OUT
12V
85
80
75
70
150mA
V
SW
FB
IN
+
47µF
LT1317
1.07M
1%
SHUTDOWN
SHDN
LB0
V
C
GND
+
C2
47µF
124k
1%
56k
3300pF
L1: SUMIDA CD54-220
1
10
100
1317 TA04
LOAD CURRENT (mA)
1317 TA04a
Single Li-Ion to 5V DC/DC Converter
Single Li-Ion to 5V DC/DC Converter Efficiency
L1
10µH
90
MBR0520
85
80
75
70
+
V
SW
FB
IN
47µF
V
OUT
LT1317
5V
1M
1%
SINGLE
Li-ION
CELL
(2.7V TO
4.2V)
250mA
SHUTDOWN
SHDN
V
GND
C
+
47µF
V
V
V
= 2.7V
= 3.5V
= 4.2V
IN
IN
IN
324k
1%
33k
3300pF
65
60
L1: SUMIDA CD43-100
1
10
100
1000
1317 TA05
LOAD CURRENT (mA)
1317 TA05a
Low Profile 3.3 to 5V Converter
L1
10µH
D1
3.3V
5V
125mA
V
SW
FB
IN
+
C1
15µF
10V
LT1317BCMS8
1M
SHDN
V
GND
C
C2
10µF
CERAMIC
33k
3.3nF
332k
C1: AVX TAJA156M010
C2: MURATA GRM235Y5V106Z01
1317 TA06
L1: MURATA LQH3C100 OR SUMIDA CLQ61-100N
D1: MOTOROLA MBR0520LT1
12
LT1317/LT1317B
U
TYPICAL APPLICATIO S
2-Cell to 5V DC/DC Converter with Undervoltage Lockout
L1
10µH
D1
5V
130mA
301k
100k
1M
V
SW
FB
1M
1%
IN
LT1317
+
22µF
10V
SHDN
V
C
LBO
LBI
2 ALKALINE
CELLS
GND
+
33k
100µF
10V
332k
1%
3.3nF
340k
470pF
D1: MOTOROLA MBR0520LT1
L1: SUMIDA CD43-101
1317 TA07
STARTS AT V = 1.9V
IN
STOPS AT V = 1.6V
IN
Universal Wall Cube to 4.1V
CERAMIC
L1A
10µF, 16V
20µH
D1
V
V
OUT
IN
1.5V TO
10V
4.1V
110mA
V
SW
FB
100k
IN
+
15µF
20V
LT1317
SHDN
V
1M
1%
L1B
GND
C
+
47µF
10V
Q1
432k
1%
33k
3.3nF
D1: MOTOROLA MBR0520LT1
L1: COILTRONICS CTX20-1
Q1: 2N3904
1317 TA08
2 Li-Ion to 8.2V DC/DC Converter
L1
22µH
D1
8.2V
400mA
+
22µF
V
SW
IN
16V
22pF
1M
LT1317/LT1317B
+
2 Li-ION
47µF
16V
FB
CELLS
(5.8V TO
8.4V)
SHUTDOWN
SHDN
V
GND
C
178k
33k
3.3nF
100pF
D1: MOTOROLA MBR0520LT1
L1: SUMIDA CD43-220
1317 TA09
13
LT1317/LT1317B
TYPICAL APPLICATIO S
U
Single Li-Ion Cell to 4V/70mA, –4V/10mA
D2
–4V
10mA
C3
15µF
+
1µF
CERAMIC
L1
22µH
4.5V TO 2.5V
C1
1µF
V
SW
L2
22µH
IN
1µF
D1
4V
CERAMIC
LT1317
1.00M
Li-Ion
CELL
SHUTDOWN
SHDN
V
FB
GND
70mA
C
+
C2
33µF
100pF
33k
3.3nF
442k
1317 TA02
C1: MURATA GRM235Y5V107Z01
C2: AVX TAJB336M010
C3: AVX TAJA156M010
D1: MBR0520
D2: BAT54S (DUAL DIODE)
L1, L2: MURATA LQH3C220K04
Low Noise 33V Varactor Bias Supply
D3
150pF
680Ω
D2
L1
22µH
C3
0.1µF
D1
V
IN
3V TO 6V
V
V
SW
FB
IN
150k
47Ω
V
OUT
33V
LT1317B
+
C1
15µF
10V
0mA TO 10mA
GND
C
+
C4
0.1µF
C2
C5
0.1µF
C6
0.1µF
10µF
35V
33k
5.9k
3300pF
C1: AVX TAJ156M010
C2: SANYO 35CV33GX
C3, C4, C5, C6: 0.1µF CERAMIC
1317 TA11
D1, D2, D3: MOTOROLA MMBD914LT1
L1: MURATA LQH3C220
14
LT1317/LT1317B
U
PACKAGE DESCRIPTION
Dimensions in inches (millimeters) unless otherwise noted.
MS8 Package
8-Lead Plastic MSOP
(LTC DWG # 05-08-1660)
0.118 ± 0.004*
(3.00 ± 0.102)
8
7
6
5
0.118 ± 0.004**
(3.00 ± 0.102)
0.192 ± 0.004
(4.88 ± 0.10)
1
2
3
4
0.040 ± 0.006
(1.02 ± 0.15)
0.034 ± 0.004
(0.86 ± 0.102)
0.007
(0.18)
0° – 6° TYP
SEATING
PLANE
0.012
(0.30)
REF
0.021 ± 0.006
(0.53 ± 0.015)
0.006 ± 0.004
(0.15 ± 0.102)
MSOP (MS8) 1197
0.0256
(0.65)
TYP
*
DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS. MOLD FLASH,
PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE
** DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS.
INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE
S8 Package
8-Lead Plastic Small Outline (Narrow 0.150)
(LTC DWG # 05-08-1610)
0.189 – 0.197*
(4.801 – 5.004)
7
5
8
6
0.150 – 0.157**
(3.810 – 3.988)
0.228 – 0.244
(5.791 – 6.197)
1
0.053 – 0.069
3
4
2
0.010 – 0.020
(0.254 – 0.508)
× 45°
(1.346 – 1.752)
0.004 – 0.010
(0.101 – 0.254)
0.008 – 0.010
(0.203 – 0.254)
0°– 8° TYP
0.016 – 0.050
0.406 – 1.270
0.050
(1.270)
TYP
0.014 – 0.019
(0.355 – 0.483)
*DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH
SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE
**DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD
FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE
SO8 0996
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 represen-
tationthattheinterconnectionofitscircuitsasdescribedhereinwillnotinfringeonexistingpatentrights.
15
LT1317/LT1317B
U
TYPICAL APPLICATION
Digital Camera Power Supply
10k
24V
D3
7
L
T1
18V
3mA
+
C5
10µF
35V
C
8
5
D2
D1
5V
20mA
+
C4
L
B
A
22µF
10V
6
3
L :15µH
PRI
2
1
3.3V
150mA
+
+
C1
22µF
10V
C2
100µF
6V
L
4
4 AA
CELLS
(3.2V TO
6.5V)
C3
1µF, 16V
V
IN
SW
LT1317
1M
SHUTDOWN
SHDN
FB
V
C
GND
10k
3300pF
604k
1317 TA10
C1, C4: AVX TPSC226M016
C2: AVX TPSC106M006
C3: CERAMIC (i.e. AVX, MANY OTHERS)
C5: SANYO 35CV10GX
D1, D2: MBR0520LT1 (MOTOROLA) OR EQUIVALENT
D3: MMBD914LT1 (MOTOROLA) OR EQUIVALENT
T1: COILTRONICS CTX02-14272-X1
RELATED PARTS
PART NUMBER
LTC®1163
LTC1174
LT1302
DESCRIPTION
COMMENTS
Triple High Side Driver for 2-Cell Inputs
Micropower Step-Down DC/DC Converter
1.8V Minimum Input, Drives N-Channel MOSFETs
94% Efficiency, 130µA I , 9V to 5V at 300mA
Q
High Output Current Micropower DC/DC Converter
2-Cell Micropower DC/DC Converter
5V/600mA from 2V, 2A Internal Switch, 200µA I
Low-Battery Detector Active in Shutdown
3.3V at 75mA from 1 Cell, MSOP Package
Q
LT1304
LT1307
Single Cell Micropower 600kHz PWM DC/DC Converter
Ultralow Power Single/Dual Comparators with Reference
2-Cell to 5V Regulated Charge Pump
LTC1440/1/2
LTC1516
LT1521
2.8µA I , Adjustable Hysteresis
Q
12µA I , No Inductors, 5V at 50mA from 3V Input
Q
Micropower Low Dropout Linear Regulator
500mV Dropout, 300mA Current, 12µA I
Q
13177bf LT/TP 1198 4K • PRINTED IN THE USA
LINEAR TECHNOLOGY CORPORATION 1998
LinearTechnology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
16
●
●
(408)432-1900 FAX:(408)434-0507 www.linear-tech.com
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