LTC7812
Low I , 38V Synchronous
Q
Boost+Buck Controller
FEATURES DESCRIPTION
n
Synchronous Boost and Buck Controllers The LTC 7812 is a high performance synchronous
n
When Cascaded, Allows V Above, Below or Equal Boost+Buck DC/DC switching regulator controller that
IN
to Regulated V drives all N-channel power MOSFET stages. It contains
OUT
n
Output Remains in Regulation Through Input Dips independent step-up (boost) and step-down (buck) control-
(e.g., Cold Crank) Down to 2.5V lers that can regulate two separate outputs or be cascaded
n
to regulate an output voltage from an input voltage that
Wide Bias Input Voltage Range: 4.5V to 38V
n
can be above, below or equal to the output voltage. The
Low Input and Output Ripple
n
LTC7812 operates from a wide 4.5V to 38V input supply
Low EMI
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range. When biased from the output of the boost regulator,
Fast Output Transient Response
n
the LTC7812 can operate from an input supply as low as
High Light Load Efficiency
n 2.5V after start-up. The 33A no-load quiescent current
Low Operating I : 33A (Both Channels On)
Q
n extends operating run time in battery-powered systems.
Low Operating I : 28A (Buck Channel On)
Q
n
R or Lossless DCR Current Sensing
SENSE
Unlike conventional buck-boost regulators, the LTC7812s
n
Buck Output Voltage Range: 0.8V V 24V
OUT
cascaded Boost+Buck solution has continuous, non-
n
Boost Output Voltage Up to 60V
pulsating, input and output currents, substantially reducing
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Phase-Lockable Frequency (75kHz to 850kHz)
voltage ripple and EMI. The LTC7812 has independent
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Small 32-Pin 5mm 5mm QFN Package
feedback and compensation points for the boost and buck
regulation loops, enabling a fast output transient response
APPLICATIONS
that can be easily optimized externally.
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Automotive and Industrial Power Systems
L, LT, LTC, LTM, Burst Mode, OPTI-LOOP and Module are registered trademarks and
n
No R is a trademark of Analog Devices, Inc. All other trademarks are the property of their
High Power Battery Operated Systems SENSE
respective owners.
TYPICAL APPLICATION
Wide Input Range to 12V/8A Low I , Cascaded Boost+Buck Regulator
Q
V
IN
5V TO 38V 2m 1H V , 14V** 4.7H 3m V
MID OUT
DOWN TO 12V
+ 33F 6.8F 6.8F + 33F 22F + 47F
2.5V AFTER 8A*
499k 499k
START-UP
46.4k 35.7k
4.7F
0.1F
0.1F
+ +
SENSE2 SENSE2 BG2 SW2 BOOST2 TG2 INTV PGND V V TG1 BOOST1 SW1 BG1 SENSE1 SENSE1 V
CC FB2 BIAS FB1
EXTV
LTC7812
CC
I I
RUN1 RUN2 TH1 TH2 TRACK/SS1 SS2 FREQ PLLIN/MODE SGND
0.1F
15k 1.86k
0.01F
100pF 820pF
* WHEN V < 8V, MAXIMUM LOAD CURRENT AVAILABLE IS REDUCED
IN
4.7nF 6.8nF
** V = 14V WHEN V < 14V
MID IN
V FOLLOWS V WHEN V > 14V 7812 TA01a
MID IN IN
7812fc
1
For more information www.linear.com/LTC7812LTC7812
ABSOLUTE MAXIMUM RATINGS PIN CONFIGURATION
(Note 1)
Bias Input Supply Voltage (V ) .............. 0.3V to 40V
BIAS
TOP VIEW
Buck Top Side Driver Voltage (BOOST1) .... 0.3V to 46V
Boost Top Side Driver Voltage (BOOST2) .... 0.3V to 76V
Buck Switch Voltage (SW1) ......................... 5V to 40V
32 31 30 29 28 27 26 25
Boost Switch Voltage (SW2) ........................ 5V to 70V
SW1 1 24 INTV
CC
INTV , (BOOST1SW1),
CC
TG1 2 23 NC
(BOOST2SW2) ...................................... 0.3V to 6V
PGOOD1 3 22 OV2
RUN1, RUN2 ............................................... 0.3V to 8V
TRACK/SS1 4 21 SGND
33
Maximum Current Sourced Into Pin
I SGND
5 PGND 20
TH1
from Source >8V ..............................................100A
V 6 19 RUN2
FB1
+
BG1, BG2, TG1, TG2 ........................................... (Note 8) SENSE1 7 18 SGND
+
SENSE1 8 17 RUN1
SENSE1 , SENSE1 Voltages ...................... 0.3V to 28V
+
9 10 11 12 13 14 15 16
SENSE2 , SENSE2 Voltages ..................... 0.3V to 40V
FREQ Voltage ........................................0.3V to INTV
CC
EXTV ...................................................... 0.3V to 14V
CC
I , I , V , V , Voltages .................... 0.3V to 6V
UH PACKAGE
TH1 TH2 FB1 FB2
32-LEAD (5mm 5mm) PLASTIC QFN
PLLIN/MODE, PGOOD1, OV2 Voltages ........ 0.3V to 6V
T = 150C, q = 44C/W
JMAX JA
TRACK/SS1, SS2 Voltages .......................... 0.3V to 6V EXPOSED PAD (PIN 33) IS PGND, MUST BE SOLDERED TO PCB
Operating Junction Temperature Range (Notes 2, 3)
LTC7812E, LTC7812I .......................... 40C to 125C
LTC7812H .......................................... 40C to 150C
Storage Temperature Range .............. 65C to 150C
ORDER INFORMATION