LT1339
High Power Synchronous
DC/DC Controller
FEATURES
s
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DESCRIPTION
The LT
®
1339 is a high power synchronous current mode
switching regulator controller. The IC drives dual
N-channel MOSFETs to create a single IC solution for high
power DC/DC converters in applications up to 60V.
The LT1339 incorporates programmable average current
limiting, allowing accurate limiting of DC load current
independent of inductor ripple current. The IC also incor-
porates user-adjustable slope compensation for minimi-
zation of magnetics at duty cycles up to 90%.
The LT1339 timing oscillator operating frequency is pro-
grammable and can be synchronized up to 150kHz. Mini-
mum off-time operation provides main switch protection.
The IC also incorporates a soft start feature that is gated by
both shutdown and undervoltage lockout conditions.
An output phase reversal pin allows flexibility in configu-
ration of converter types, including inverting and negative
topologies.
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High Voltage: Operation Up to 60V
High Current: Dual N-Channel Synchronous Drive
Handles Up to 10,000pF Gate Capacitance
Programmable Average Load Current Limiting
5V Reference Output with 10mA External
Loading Capability
Programmable Fixed Frequency Synchronizable
Current Mode Operation Up to 150kHz
Undervoltage Lockout with Hysteresis
Programmable Start Inhibit for Power Supply
Sequencing and Protection
Adaptive Nonoverlapping Gate Drive Prevents
Shoot-Through
APPLICATIONS
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48V Telecom Power Supplies
Personal Computers and Peripherals
Distributed Power Converters
Industrial Control Systems
Lead-Acid Battery Backup Systems
Automotive and Heavy Equipment
, LTC and LT are registered trademarks of Linear Technology Corporation.
TYPICAL APPLICATION
28V to 5V 20A Buck Converter
DBST
IN5819
SYNC
5V
REF
V
BOOST
V
IN
28V
+
+
R
CT
10k
C
AVG
C
CT
2200pF 2200pF
C
SS
, 1µF
C
VC
, 1nF
CT
SL/ADJ
LT1339
I
AVG
TG
TS
12V
IN
BG
PGND
PHASE
V
C
SGND
V
FB
V
REF
R
FB2
1k
SENSE
–
R
FB1
3k
RUN/SHDN
SENSE
+
+
CBST
1µF
D1
MBR0520
12V
C
12VIN
47µF
IRL3803
+
C
IN
1500µF
63V
×
3
EFFICIENCY (%)
C
5VREF
1µF
D2
MBR0520
R
RUN
100k
IRL3103D2
×
2
L1
10µH
+
SS
R
VC
, 10k
C
REF
0.1µF
R
S
0.005Ω
+
L1 = CTX02-13400-X2
C
OUT
2200µF
6.3V
×
2
U
U
U
28V to 5V Efficiency
100
90
80
70
60
50
0
10
5
15
OUTPUT CURRENT (A)
20
1339 TA03a
V
OUT
5V AT 20A
1339 TA03
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1
LT1339
ABSOLUTE
(Note 1)
AXI U
RATI GS
PACKAGE/ORDER I FOR ATIO
TOP VIEW
SYNC 1
5V
REF
2
CT 3
SL/ADJ 4
I
AVG
5
SS 6
V
C
7
SGND 8
V
FB
9
V
REF
10
N PACKAGE
20-LEAD PDIP
20 V
BOOST
19 TG
18 TS
17 12V
IN
16 BG
15 PGND
14 PHASE
13 RUN/SHDN
12 SENSE
–
11 SENSE
+
SW PACKAGE
20-LEAD PLASTIC SO WIDE
Supply Voltages
Power Supply Voltage (12V
IN
)...............– 0.3V to 20V
Topside Supply Voltage (V
BOOST
)
V
TS
– 0.3V to V
TS
+ 20V (V
MAX
= 75V)
Topside Reference Pin Voltage (TS) ......– 0.3V to 60V
Input Voltages
Sense Amplifier Input Common Mode ...– 0.3V to 60V
RUN/SHDN Pin Voltage ...................... – 0.3V to 12V
IN
All Other Inputs .......................................– 0.3V to 7V
Maximum Currents
5V Reference Output Current............................ 65mA
Maximum Temperatures
Operating Ambient Temperature Range
LT1339C ............................................ 0°C to 70°C
LT1339I ......................................... – 40°C to 85°C
Storage Temperature Range ................. – 65°C to 150°C
Lead Temperature (Soldering, 10 sec).................. 300°C
ORDER PART
NUMBER
LT1339CN
LT1339CSW
LT1339IN
LT1339ISW
T
JMAX
= 125°C,
θ
JA
= 70°C/W (N)
T
JMAX
= 125°C,
θ
JA
= 85°C/W (SW)
Consult factory for Military grade parts.
ELECTRICAL CHARACTERISTICS
12V
IN
= V
BOOST
= 12V, V
C
= 2V, TS = 0V, V
FB
= V
REF
= 1.25V, C
TG
= C
BG
= 3000pF, T
A
= 25°C unless otherwise noted.
SYMBOL
I
12VIN
I
BOOST
PARAMETER
DC Active Supply Current (Note 2)
DC Standby Supply Current
DC Active Supply Current (Note 2)
DC Standby Supply Current
Shutdown Threshold Hysteresis
Soft Start Charge Current
Undervoltage Lockout Threshold - Falling
Undervoltage Lockout Threshold - Rising
Undervoltage Lockout Hysteresis
5V Reference Voltage
5V Reference Line Regulation
I
REF5
5V Reference Load Range - DC
Pulse
5V Reference Load Regulation
I
SC
5V Reference Short-Circuit Current
0
≤
I
REF5
≤
20mA
Line, Load and Temperature
10V
≤
12V
IN
≤
15V
q
q
q
q
CONDITIONS
q
q
MIN
TYP
14
150
2.2
0
MAX
20
250
UNITS
mA
µA
mA
µA
Supply and Protection
V
RUN/SHDN
< 0.5V
V
RUN/SHDN
< 0.5V
q
V
RUN/SHDN
Shutdown Rising Threshold
V
SSHYST
I
SS
V
UVLO
1.15
4
8.20
200
4.75
1.25
25
8
9.00
9.35
350
5.00
3
1.35
14
9.75
9.95
5V Reference
V
REF5
q
q
q
q
q
5.25
5
10
20
mV/V
mA
mA
V/A
mA
– 1.25
45
–2
sn1339 1339fas
2
U
V
mV
µA
V
V
mV
V
W
U
U
W W
W
LT1339
ELECTRICAL CHARACTERISTICS
12V
IN
= V
BOOST
= 12V, V
C
= 2V, TS = 0V, V
FB
= V
REF
= 1.25V, C
TG
= C
BG
= 3000pF, T
A
= 25°C unless otherwise noted.
SYMBOL
V
FB
I
FB
g
m
A
V
I
VC
V
VC
V
SENSE
V
IAVG
A
V
V
OS
I
B
Oscillator
f
O
I
CT
V
SYNC
f
SYNC
V
TG,BG
V
TG
t
TGR
t
TGF
V
BG
t
BGR
t
BGF
Operating Frequency, Free Run
Frequency Programming Error (Note 3)
Timing Capacitor Discharge Current
SYNC Input Threshold
SYNC Frequency Range
Undervoltage Output Clamp
Standby Mode Output Clamp
Top Gate On Voltage
Top Gate Off Voltage
Top Gate Rise Time
Top Gate Fall Time
Bottom Gate On Voltage
Bottom Gate Off Voltage
Bottom Gate Rise Time
Bottom Gate Fall Time
f
O
≤
150kHz
LT1339C
LT1339I
Rising Edge
f
SYNC
≤
150kHz
12V
IN
≤
8V
V
RUN
< 0.5V
q
q
q
q
q
q
PARAMETER
Error Amplifier Reference Voltage
Feedback Input Current
Error Amplifier Transconductance
Error Amplifier Voltage Gain
Error Amplifier Source Current
Error Amplifier Sink Current
Absolute V
C
Clamp Voltage
Peak Current Limit Threshold
Average Current Limit Threshold (Note 4)
Average Current Limit Threshold
Amplifier DC Gain
Amplifier Input Offset Voltage
Input Bias Current
CONDITIONS
Measured at Feedback Pin
q
MIN
1.242
1.235
0.1
1200
1500
200
280
170
110
TYP
1.250
1.250
0.5
2000
3000
275
400
3.5
190
120
2.5
15
MAX
1.258
1.265
1.0
3200
UNITS
V
V
µA
µmho
V/V
µA
µA
V
mV
mV
V
V/V
mV
Error Amplifier
V
FB
= V
REF
q
q
q
V
FB
– V
REF
= 500mV
Measured at V
C
Pin
Measured at Sense Inputs
Measured at Sense Inputs
Measured at I
AVG
Pin
Measured at I
AVG
Pin
2V < V
CMSENSE
< 60V,
SENSE
+
– SENSE
–
= 5mV
Sink (V
CMSENSE
> 5V)
Source (V
CMSENSE
= 0V)
q
q
q
q
130
Current Sense Amplifier
q
q
q
0.1
45
700
75
1200
150
5
2.50
2.50
2.75
2.75
2.0
1.4f
O
0.4
11.0
11.9
0.4
130
60
11.0
11.9
0.4
70
60
0.7
0.1
12.0
0.7
200
140
12.0
0.7
200
140
µA
µA
kHz
%
mA
mA
V
–5
2.20
2.10
0.8
f
O
Output Drivers
q
q
q
q
q
q
q
q
q
q
V
V
V
V
ns
ns
V
V
ns
ns
The
q
denotes specifications which apply over the full operating
temperature range.
Note 1:
Absolute maximum ratings are those values beyond which the life
of a device may be impaired.
Note 2:
Supply current specification does not include external FET gate
charge currents. Actual supply currents will be higher and vary with
operating frequency, operating voltages and the type of external FETs
used. See Application Information section.
Note 3:
Test condition: R
CT
= 16.9k, C
CT
= 1000pF.
Note 4:
Test Condition: V
CMSENSE
= 10V.
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LT1339
TYPICAL PERFORMANCE CHARACTERISTICS
Boost Supply Current vs
Temperature
4.0
BOOST SUPPLY CURRENT (mA)
3.5
3.0
2.5
2.0
1.5
1.0
–50 –25
18
17
I
12VIN
SUPPLY CURRENT (mA)
16
15
14
13
12
11
50
25
75
0
TEMPERATURE (°C)
100
125
10
–50 –25
0
25
50
75
100
125
5V REFERENCE SHORT-CIRCUIT CURRENT (mA)
I
12VIN
Shutdown Current vs
Temperature
190
I
12VIN
SHUTDOWN CURRENT (µA)
180
REFERENCE VOLTAGE (V)
170
160
150
140
130
–50 –25
1.252
1.251
1.250
1.249
1.248
1.247
5V REFERENCE VOLTAGE (V)
50
25
75
0
TEMPERATURE (°C)
Error Amplifier Voltage Gain vs
Temperature
4.5
ERROR AMPLIFIER VOLTAGE GAIN (kV/V)
4.0
3.5
3.0
2.5
2.0
1.5
1.0
–50 –25
ERROR AMPLIFIER TRANSCONDUCTANCE (m )
2.6
2.4
2.2
2.0
1.8
1.6
Ω
ERROR AMPLIFIER SOURCE CURRENT (µA)
50
25
75
0
TEMPERATURE (°C)
4
U W
1339 G01
12V
IN
Supply Current vs
Temperature
60
55
50
45
40
35
5V Reference Short-Circuit
Current vs Temperature
30
–50 –25
TEMPERATURE (°C)
1339 G02
50
25
75
0
TEMPERATURE (°C)
100
125
1339 G03
Reference Voltage vs
Temperature
5.01
5V Reference Voltage vs
Temperature
5.00
4.99
100
125
1.246
–50 –25
50
25
75
0
TEMPERATURE (°C)
100
125
4.98
–50 –25
50
25
75
0
TEMPERATURE (°C)
100
125
1339 G04
1339 G05
1339 G06
Error Amplifier Transconductance
vs Temperature
350
325
300
275
250
225
Error Amplifier Maximum Source
Current vs Temperature
100
125
1.4
–50 –25
50
25
75
0
TEMPERATURE (°C)
100
125
200
–50 –25
50
25
75
0
TEMPERATURE (°C)
100
125
1339 G07
1339 G08
1339 G09
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LT1339
TYPICAL PERFORMANCE CHARACTERISTICS
Soft Start Charge Current
vs Temperature
9
SOFT START CHARGE CURRENT (µA)
RUN/SHDN RISING THRESHOLD (V)
1.26
1.25
1.24
1.23
1.22
1.21
1.20
–50 –25
RUN/SHDN THRESHOLD HYSTERESIS (mV)
50
25
75
0
TEMPERATURE (°C)
100
125
8
7
6
–50 –25
50
25
75
0
TEMPERATURE (°C)
Bottom Gate Transition Times vs
Bottom Gate Capacitance
160
300
T
A
= 25°C
BOTTOM GATE TRANSITION TIMES (ns)
TOP GATE TRANSITION TIMES (ns)
140
120
100
80
60
V
SENSE
(mV)
RISE TIME
FALL TIME
40
20
0
1000
5000
7500
2500
BOTTOM GATE CAPACITANCE (pF)
10000
1339 G13
12V
IN
Supply Current vs
Supply Voltage
30
18
28
12V
IN
SUPPLY CURRENT (mA )
BOOST SUPPLY CURRENT (mA )
f
O
= 100kHz
T
A
= 25°C
C
BG
= 10000pF
26
24
22
20
18
16
14
10
12
13
14
11
12V
IN
SUPPLY VOLTAGE (V)
U W
100
125
1339 G10
RUN/SHDN Rising Threshold
vs Temperature
26
25
24
23
22
21
RUN/SHDN Threshold Hysteresis
vs Temperature
20
–50 –25
50
25
75
0
TEMPERATURE (°C)
100
125
1339 G11
1339 G12
Top Gate Transition Times vs
Top Gate Capacitance
160
T
A
= 25°C
250
200
150
100
FALL TIME
50
0
1000
Average Current Limit Threshold
Sense Voltage Tolerance vs
Common Mode Voltage
150
140
UPPER LIMIT
FULL OPERATING
TEMPERATURE RANGE
RISE TIME
130
120
110
100
90
80
TYPICAL
LOWER LIMIT
5000
7500
2500
TOP GATE CAPACITANCE (pF)
10000
1339 G14
0
1
2
3
4
5
60
1339 G15
V
SENSE(CM)
(V)
Boost Supply Current vs
12V
IN
Supply Voltage
16
14
12
10
C
TG
= 4700pF
8
6
4
2
15
1339 G16
f
O
= 100kHz
T
A
= 25°C
C
TG
= 10000pF
C
BG
= 4700pF
C
BG
= 3300pF
C
BG
= 1000pF
C
TG
= 3300pF
C
TG
= 1000pF
10
12
13
14
11
12V
IN
SUPPLY VOLTAGE (V)
15
1339 G17
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