LT1680
High Power DC/DC
Step-Up Controller
FEATURES
DESCRIPTIO
n
The LT 1680 is a high power, current mode switching
High Voltage: Operation Up to 60V
n
power supply controller optimized for boost topologies.
High Current: N-Channel Drive Handles Up to
The IC drives an N-channel MOSFET switch for DC/DC
10,000pF Gate Capacitance
n converter applications up to 60V input. A high current gate
Programmable Average Current Limiting
drive output handles up to 10,000pF gate capacitance,
n
5V Reference Output with 10mA External
enabling the construction of high power DC/DC convert-
Loading Capability
ers. Current sense common mode range up to 60V allows
n
Fixed Frequency Current Mode Operation
current sensing to be referenced to the input supply,
n
Oscillator Synchronizable Up to 200kHz
eliminating the need for sense blanking circuits.
n
Undervoltage Lockout with Hysteresis
n
Programmable Start Inhibit for Power Supply
The LT1680 incorporates programmable average current
Sequencing and Protection limiting allowing accurate limiting of DC current in the
n
User Adjustable Slope Compensation magnetics, independent of ripple current . User adjustable
slope compensation provides stable operation at duty
U
cycles up to 90%.
APPLICATIO S
The LT1680 operating frequency is programmable and
n
High Power Single Board Systems
can be synchronized up to 200kHz. Minimum off-time
n
Distributed Power Converters operation provides switch protection. The IC also incorpo-
n
Industrial Control Systems
rates a soft start feature that is gated by both shutdown
n
and undervoltage lockout conditions.
Lead-Acid Battery Back-Up Systems
n
, LTC and LT are registered trademarks of Linear Technology Corporation.
Automotive and Heavy Equipment
TYPICAL APPLICATIO
12V to 48V, 250W Boost Converter
12V
IN
10V TO 15V
R
SENSE
C2 24A (DC)
Efficiency vs Output Power
0.005W
1m F
100
C
IN V = 48V
+
OUT
680m F
R LT1680
CT L1
25V
C 15k
CT
25m H
1 16
95
4
1nF SL/ADJ 5V
REF
2 15
+
C SYNC
T
C12
3 14
C3 220pF
90
1m F
I 12V
AVG IN
M1
C4 0.22m F
4 13
SS GATE IRFZ44
5 12 3
85
C 4.7nF
V PGND
VC C
R9
6 11
100k
R 4.7k SGND RUN/SHDN
VC
MBR0520
7 10
80
V SENSE
FB
8 9 C11 1nF
+
D1
V SENSE
REF
R7 R6
MBR20100CT
75
C6 0.1m F V
2k 75k
2 OUT
0 50 100 150 200 250
48V
C OUTPUT POWER (W)
OUT 5.2A
+
680m F
1680 TA02
L1: Kool Mm , 18T #14 ON 77314-A7
63V
Kool Mm IS A REGISTERED TRADEMARK OF MAGNETICS, INC. 3 1680 TA01
1
EFFICIENCY (%)
U
ULT1680
UUW
ABSOLUTE AXI U RATI GS
PACKAGE/ORDER I FOR ATIO
(Note 1)
TOP VIEW
ORDER PART
Power Supply Voltage (12V ) .................. 0.3V to 20V
IN
NUMBER
SL/ADJ 1 16 5V
REF
Sense Amplifier Input Common Mode ...... 0.3V to 60V
C 2 15 SYNC
T
LT1680CN
GATE Pin Voltage....................... 0.3V to 12V + 0.3V
IN
I 3 14 12V
AVG IN
LT1680CSW
RUN/SHDN Pin Voltage ......................... 0.3V to 12V
IN
SS 4 13 GATE
LT1680IN
All Other Pin Voltages ................................. 0.3V to 7V
V 5 12 PGND
C
LT1680ISW
5V Reference Output Current ............................... 65mA
SGND 6 11 RUN/SHDN
Operating Ambient Temperature Range V 7 10 SENSE
FB
+
V 8 9 SENSE
LT1680C .................................................. 0 C to 70 C
REF
LT1680I .............................................. 40 C to 85 C
N PACKAGE SW PACKAGE
16-LEAD PDIP 16-LEAD PLASTIC SO WIDE
Storage Temperature Range ................ 65 C to 150 C
T = 125 C, q = 75 C/ W (N)
JMAX JA
Lead Temperature (Soldering, 10 sec)................. 300 C
T = 125 C, q = 90 C/ W (SW)
JMAX JA
Consult factory for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS
The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at T = 25 C.
A
12V = 12V, V = 2V, V = V = 1.25V, C = 3000pF, unless otherwise noted.
IN VC FB REF GATE
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
Supply and Protection
I DC Active Supply Current (Note 2) Gate Output On l 15 22 mA
12VIN
Gate Output Off 12 mA
DC Standby Supply Current V < 0.5V l 150 250 m A
RUN
V Shutdown Rising Threshold l 1.15 1.25 1.35 V
RUN/SHDN
V Shutdown Threshold Hysteresis 25 mV
SSHYST
I Soft Start Charge Current l 58 14 m A
SS
V Undervoltage Lockout Threshold - Falling l 8.20 9.00 9.75 V
UVLO
Undervoltage Lockout Threshold - Rising l 9.35 9.95 V
Undervoltage Lockout Hysteresis l 200 350 mV
5V Reference
V 5V Reference Voltage Line, Load and Temperature l 4.75 5 5.25 V
REF5
5V Reference Line Regulation 10V 12V 15V l 3 5 mV/V
IN
I 5V Reference Load Range - DC l 10 mA
REF5
Pulse l 20 mA
5V Reference Load Regulation 0 I 20mA l 1.25 2 V/A
REF5
I 5V Reference Short-Circuit Current 45 mA
SC
Error Amplifier
V Error Amplifier Reference Voltage Measured at Feedback Pin 1.242 1.250 1.258 V
FB
l 1.235 1.265 V
I Feedback Input Current V = V l 0.1 0.5 1.0 m A
FB FB REF
g Error Amplifier Transconductance l 1200 2000 3200 m mho
m
A Error Amplifier Voltage Gain l 1500 3000 V/V
V
I Error Amplifier Source Current l 200 275 m A
VC
Error Amplifier Sink Current V V = 500mV l 280 400 m A
FB REF
V Absolute V Clamp Voltage Measured at V Pin 3.5 V
VC C C
2
U WWW