LT1302/LT1302-5
Micropower
High Output Current
Step-Up Adjustable and
Fixed 5V DC/DC Converters
FEATURES
s
s
s
s
s
s
DESCRIPTIO
s
s
5V at 600mA or 12V at 120mA from 2-Cell Supply
200µA Quiescent Current
Logic Controlled Shutdown to 15µA
Low V
CESAT
Switch: 310mV at 2A Typical
Burst Mode
TM
Operation at Light Load
Current Mode Operation for Excellent
Line and Load Transient Response
Available in 8-Lead SO or PDIP
Operates with Supply Voltage as Low as 2V
The LT
®
1302/LT1302-5 are micropower step-up DC/DC
converters that maintain high efficiency over a wide
range of output current. They operate from a supply
voltage as low as 2V and feature automatic shifting
between Burst Mode operation at light load, and current
mode operation at heavy load.
The internal low loss NPN power switch can handle
current in excess of 2A and switch at frequencies up to
400kHz. Quiescent current is just 200µA and can be
further reduced to 15µA in shutdown.
Available in 8-pin PDIP or 8-pin SO packaging, the LT1302/
LT1302-5 have the highest switch current rating of any
similarly packaged switching regulators presently on the
market.
, LTC and LT are registered trademarks of Linear Technology Corporation.
APPLICATI
s
s
s
s
s
S
Notebook and Palmtop Computers
Portable Instruments
Personal Digital Assistants
Cellular Telephones
Flash Memory
Burst Mode is a trademark of Linear Technology Corporation.
TYPICAL APPLICATI
L1
10µH
6
7
V
IN
SW
PGND
GND
1
NC
5
I
T
SHDN
3
4
SHUTDOWN
2-Cell to 5V Converter Efficiency
90
88
86
EFFICIENCY (%)
2 CELLS
+
C1
100µF
C3
0.1µF
D1
LT1302-5
8
SENSE
V
C
84
82
80
78
76
74
+
C2
100µF
2
R
C
20k
C
C
0.01µF
OUTPUT
5V
600mA
C1 = C2 = SANYO OS-CON
L1 = COILTRONICS CTX10-3
COILCRAFT DO3316-103
72
LT1302 • F01
70
1
10
100
LOAD CURRENT (mA)
1000
LT1302 • TA02
D1 = MOTOROLA MBRS130LT3
Figure 1. 2-Cell to 5V/600mA DC/DC Converter
U
V
IN
= 3V
V
IN
= 2.5V
V
IN
= 2V
UO
UO
1
LT1302/LT1302-5
ABSOLUTE
AXI U
RATI GS
PACKAGE/ORDER I FOR ATIO
TOP VIEW
GND 1
V
C
2
SHDN 3
(SENSE*)FB 4
8
7
6
5
PGND
SW
V
IN
I
T
V
IN
Voltage ............................................................. 10V
SW Voltage ............................................................. 25V
FB Voltage .............................................................. 10V
SHDN Voltage ......................................................... 10V
V
C
Voltage ................................................................ 4V
I
T
Voltage .................................................................. 4V
Maximum Power Dissipation ............................ 700mW
Operating Temperature Range .................... 0°C to 70°C
Storage Temperature Range ............... – 65°C to 150°C
Lead Temperature (Soldering, 10 sec)................. 300°C
ORDER PART
NUMBER
LT1302CN8
LT1302CS8
LT1302CN8-5
LT1302CS8-5
S8 PART MARKING
1302
13025
N8 PACKAGE
S8 PACKAGE
8-LEAD PDIP
8-LEAD PLASTIC SO
*FIXED VERSION
PINS 1 AND 8 ARE INTERNALLY
CONNECTED IN SOIC PACKAGE
T
JMAX
= 125°C,
θ
JA
= 100°C/W (N8)
T
JMAX
= 125°C,
θ
JA
= 80°C/W (S8)
Consult factory for Industrial and Military grade parts.
DC ELECTRICAL CHARACTERISTICS
SYMBOL
I
Q
V
IN
V
FB
PARAMETER
Quiescent Current
Input Voltage Range
T
A
= 25°C, V
IN
= 2.5V, unless otherwise noted.
MIN
q
q
q
CONDITIONS
V
SHDN
= 0.5V, V
FB
= 1.3V
V
SHDN
= 1.8V
TYP
200
15
MAX
300
25
8
1.26
5.25
V
OS
Feedback Voltage (LT1302)
Feedback Pin Bias Current (LT1302)
Output Sense Voltage (LT1302-5)
Output Ripple Voltage (LT1302-5)
Sense Pin Resistance to Ground (LT1302-5)
Offset Voltage
Comparator Hysteresis
Oscillator Frequency
Maximum Duty Cycle
Switch On Time
Switch Off Time
Output Line Regulation
Switch Saturation Voltage
Switch Leakage Current
Switch Current Limit
Error Amplifier Voltage Gain
Shutdown Pin High
Shutdown Pin Low
Shutdown Pin Bias Current
V
C
= 0.4V
V
FB
= 1V
V
C
= 0.4V
V
C
= 0.4V
See Block Diagram
(Note 1)
Current Limit Not Asserted (Note 2)
q
q
2.0
2.2
1.22
4.85
q
DC
t
ON
t
OFF
V
CESAT
175
160
75
1.24
100
5.05
50
420
15
5
220
86
3.9
0.7
0.06
310
0.1
1
2.8
75
265
310
95
Current Limit Not Asserted
2 < V
IN
< 8V
I
SW
= 2A
V
SW
= 5V, Switch Off
V
C
= 0.4V (Burst Mode Operation)
V
C
= 1.25V (Full Power) (Note 3)
0.9V
≤
V
C
≤
1.2V,
∆V
C
/∆V
FB
q
q
q
q
q
q
0.15
400
475
10
3.9
V
SHDNH
V
SHDNL
I
SHDN
2.0
50
1.8
V
SHDN
= 5V
V
SHDN
= 2V
V
SHDN
= 0V
q
q
I
T
Pin Resistance to Ground
The
q
denotes specifications which apply over the 0°C to 70°C
temperature range.
Note 1:
Hysteresis is specified at DC. Output ripple depends on capacitor
size and ESR.
8
3
0.1
3.9
0.5
20
1
UNITS
µA
µA
V
V
V
nA
V
mV
kΩ
mV
mV
kHz
kHZ
%
µs
µs
%/V
mV
mV
µA
A
A
V/ V
V
V
µA
µA
µA
kΩ
Note 2:
The LT1302 operates in a variable frequency mode. Switching
frequency depends on load inductance and operating conditions and may
be above specified limits.
Note 3:
Minimum switch current 100% tested. Maximum switch current
guaranteed by design.
2
U
W
U
U
W W
W
LT1302/LT1302-5
TYPICAL PERFORMANCE CHARACTERISTICS
No-Load Quiescent Current
Circuit of Figure 1
500
450
QUIESCENT CURRENT (µA)
T
A
= 25°C
500
400
350
300
250
200
150
100
50
0
2.0
SATURATION VOLTAGE (mV)
400
V
CESAT
(V)
2.5
3.0
3.5
4.0
SUPPLY VOLTAGE (V)
LT1302 Feedback Voltage
1.250
1.245
600
500
1.235
1.230
1.225
1.220
1.215
1.210
1.205
1.200
–50
–25
0
25
50
TEMPERATURE (°C)
75
100
QUIESCENT CURRENT (µA)
SENSE RESISTANCE (kΩ)
1.240
FEEDBACK VOLTAGE (V)
Error Amplifier Offset Voltage
30
25
OFFSET VOLTAGE (mV)
OUTPUT VOLTAGE (V)
5.025
5.000
4.975
4.950
4.925
4.900
–50
–25
0
25
50
TEMPERATURE (°C)
75
100
ON-TIME (µs)
20
15
10
5
0
–50
–25
0
25
50
TEMPERATURE (°C)
U W
4.5
1302 G01
1302 G04
Switch Saturation Voltage
600
T
A
= 25°C
350
300
250
200
150
400
Switch Saturation Voltage
I
SW
= 2A
300
200
100
0
5.0
0
1
2
3
SWITCH CURRENT (A)
4
1302 G02
100
–50
–25
0
25
50
TEMPERATURE (°C)
75
100
1302 G03
LT1302-5 Sense Pin Resistance
300
250
200
150
100
50
Quiescent Current
V
IN
= 2.5V
SWITCH OFF
400
300
200
100
0
–50
–25
0
25
50
TEMPERATURE (°C)
75
100
0
–50
–25
0
25
50
TEMPERATURE (°C)
75
100
1302 G05
1302 G06
LT1302-5 Output Voltage
5.100
5.075
5.050
4.0
3.5
3.0
2.5
5.0
4.5
Maximum On-Time
75
100
2.0
–50
–25
0
25
50
TEMPERATURE (°C)
75
100
1302 G07
1302 G08
1302 G09
3
LT1302/LT1302-5
TYPICAL PERFORMANCE CHARACTERISTICS
Maximum Duty Cycle
100
300
275
SHUTDOWN CURRENT (µA)
FREQUENCY (kHz)
90
DUTY CYCLE (%)
80
70
60
50
–50
–25
0
25
50
TEMPERATURE (°C)
LT1302-5 Output Voltage vs
Load Current
5.20
5.15
20
OUTPUT VOLTAGE (V)
5.05
5.00
4.95
4.90
V
IN
= 2.2V
V
IN
= 4V
V
IN
= 3V
OUTPUT POWER (W)
5.10
4.85
4.80
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
LOAD CURRENT (A)
1302 G13
PI FU CTIO S
GND (Pin 1):
Signal Ground. Feedback resistor and 0.1µF
ceramic bypass capacitor from V
IN
should be connected
directly to this pin.
V
C
(Pin 2):
Frequency Compensation Pin. Connect series
RC to GND. Keep trace short.
SHDN (Pin 3):
Shutdown. Pull high to effect shutdown; tie
to ground for normal operation.
FB/Sense (Pin 4):
Feedback/Sense. On the LT1302 this
pin connects to CMP1 input. On the LT1302-5 this pin
connects to the output resistor string.
I
T
(Pin 5):
Normally left floating. Addition of a 3.3k resistor
to GND forces the LT1302 into current mode at light loads.
Efficiency drops at light load but increases at medium
loads. See Applications Information section.
V
IN
(Pin 6):
Supply Pin. Must be bypassed with: (1) a 0.1µF
ceramic to GND, and (2) a large value electrolytic to PGND.
When V
IN
is greater than 5V, a low value resistor (2Ω to
10Ω) is recommended to isolate the V
IN
pin from input
supply noise.
4
U W
75
1302 G10
Oscillator Frequency
20
18
16
14
12
10
8
6
4
2
Shutdown Pin Bias Current
T
A
= 25°C
250
225
200
175
150
–50
100
–25
0
25
50
TEMPERATURE (°C)
75
100
0
0
1
6
4
2
3
5
SHUTDOWN VOLTAGE (V)
7
8
1302 G11
1302 G12
Maximum Output Power*
Boost Mode
16
12
8
4
0
0
2
6
4
INPUT VOLTAGE (V)
8
10
1302 G14
* APPROXIMATE
U
U
U
LT1302/LT1302-5
PI FU CTIO S
SW (Pin 7):
Switch Pin. Connect inductor and diode here.
Keep layout short and direct.
PGND (Pin 8):
Power Ground. Pins 8 and 1 should be
connected under the package. In the SO package, pins 1
and 8 are thermally connected to the die. One square inch
of PCB copper provides an adequate heat sink for the
device.
BLOCK DIAGRA SM
L1
V
IN
C1
D1
+
6
V
IN
1.24V
REFERENCE
R1
4
C5
100pF
R2
FB
V
OS
15mV
SHDN
3
SHUTDOWN
W
U
U
U
C2
0.1µF
7
SW
+
V
OUT
C3
36mV
+
A2
R4
1.75Ω
R5
730Ω
–
+
–
CMP1
ENABLE
OFF
220kHz
OSCILLATOR
A3
DRIVER
Q3
Q4
160X
HYSTERETIC
COMPARATOR 2
µA
V
IN
Q5
V
IN
Q1
ERROR
AMPLIFIER
300Ω
Q2
–
A1
BIAS
+
3.6k
1
GND
2
V
C
R3
22k
C4
0.01µF
5
I
T
8
PGND
1302 F02
Figure 2. LT1302 Block Diagram
5
嵌入式系统
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