LT3694-1_15 Datasheet, PDF (1/28 Pages) Linear Technology – 36V, 2.6A Monolithic Buck Regulator With Dual LDO

FEATURES
n _{Wide Input Range: 4V to 36V}
n _{Overvoltage Shutdown Protects Circuit Through}
70V Transients
n _{2.6A Output Switching Regulator with Internal}
Power Switch
n _{Dual, Low Dropout, Linear Regulator Controllers}
with Programmable Current Limit
n _{Tracking/Soft-Start Inputs and Power Good Output}
Simplify Soft-Start and Supply Sequencing
n _{Uses Small Inductors and Ceramic Capacitors}
n _{VOUT(MIN) = 0.75V (Buck and LDOs)}
n _{Adjustable 250kHz to 2.5MHz Switching Frequency}
n _{Accurate Enable Threshold Allows User}
Programmable Undervoltage Lockout
n _{Options for Clock Synchronization (LT3694) or Clock}
Output to Enable Synchronization to Other Switching
Regulators (LT3694-1)
n _{Thermally Enhanced 28-Lead 4mm × 5mm QFN and}
20-Lead TSSOP Packages
APPLICATIONS
n _Automotive
n _Industrial
n _{DSL and Cable Modems}
n _{Distributed Power Regulation}
n _{Wall Transformer Regulation}
LT3694/LT3694-1
36V, 2.6A Monolithic Buck
Regulator With Dual LDO
DESCRIPTION
The LT^®3694/LT3694-1 are monolithic, current mode
DC/DC converters with dual, low dropout regulator con-
trollers. The switching converter is a step-down converter
capable of generating up to 2.6A at its output. Each regu-
lator has independent track/soft-start circuits simplifying
power supply sequencing and interfacing with micro-
controllers and DSPs.
The switching frequency is set with a single resistor with a
range of 250kHz to 2.5MHz. The high switching frequency
permits the use of small inductors and ceramic capacitors
leading to very small triple output solutions. The constant-
switching frequency, combined with low impedance ce-
ramic capacitors, results in low, predictable output ripple.
Protection circuitry senses the current in the power switch
and external Schottky catch diode to protect the LT3694
against short-circuit conditions. Frequency foldback and
thermal shutdown provide additional protection.
With its wide input voltage range of 4V to 36V, the LT3694
regulates a broad array of power sources from 4-cell batteries
and 5V logic rails to unregulated wall transformers, lead acid
batteries and distributed power supplies. The LT3694 can be
synchronized to an external clock with the SYNC pin while
the LT3694-1 offers a CLKOUT pin allowing other DC/DC
converters to synchronize to the LT3694-1 clock.
L, LT, LTC, LTM, Linear Technology, the Linear logo and Burst Mode are registered trademarks
of Linear Technology Corporation. All other trademarks are the property of their respective owners.
TYPICAL APPLICATION
V_IN
4.5V TO 36V
OUT1
OUT2
2.5V
450mA
4.7µF
EN/UVLO VIN BIAS BST
0.1Ω
TRK/SS1
1nF
TRK/SS2
TRK/SS3
LIM2
LT3694
DRV2
2.2µF
24.9k
10.7k
51.1k
FB2
SYNC
PGOOD
RT
GND
f_SW = 800kHz
SW
DA
FB1
V_C1
LIM3
DRV3
FB3
0.22µF _4.7µH
B340A
34k
330pF
41.2k
10k
OUT1
3.3V
1.7A
47µF
0.1Ω
15.4k
OUT1
OUT3
1.8V
2.2µF ^450mA
11k
36941 TA01a
Efficiency at V_OUT = 3.3V
100
V_IN = 4.5V
90
V_IN = 12V
80
V_IN = 36V
f_SW = 800kHz
70
60
50
0
1
2
I_OUT (A)
3
36941 TA01b
36941fb
1