LT3976_15 Datasheet, PDF (1/28 Pages) Linear Technology – 40V, 5A, 2MHz Step-Down Switching Regulator with 3.3A Quiescent Current

LT3976
40V, 5A, 2MHz Step-Down
Switching Regulator with
3.3µA Quiescent Current
Features
n _{Ultralow Quiescent Current:}
3.3µA I_Q at 12V_IN to 3.3V_OUT
n _{Low Ripple Burst Mode}^® _Operation
Output Ripple < 15mV_P-P
n _{Wide Input Range: Operation from 4.3V to 40V}
n _{5A Maximum Output Current}
n _{Excellent Start-Up and Dropout Performance}
n _{Adjustable Switching Frequency: 200kHz to 2MHz}
n _{Synchronizable Between 250kHz to 2MHz}
n _{Accurate Programmable Undervoltage Lockout}
n _{Low Shutdown Current: IQ = 700nA}
n _{Power Good Flag}
n _{Soft-Start Capability}
n _{Thermal Shutdown Protection}
n _{Current Limit Foldback with Soft-Start Override}
n _{Saturating Switch Design: 75mΩ On-Resistance}
n _{Small, Thermally Enhanced 16-Lead MSOP and}
24-Lead 3mm × 5mm QFN Packages
Applications
n _{Automotive Battery Regulation}
n _{Portable Products}
n _{Industrial Supplies}
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.
Description
The LT^®3976 is an adjustable frequency monolithic buck
switching regulator that accepts a wide input voltage range
up to 40V. Low quiescent current design consumes only
3.3µA of supply current while regulating with no load. Low
ripple Burst Mode operation maintains high efficiency at
low output currents while keeping the output ripple below
15mV in a typical application. The LT3976 can supply up
to 5A of load current and has current limit foldback to
limit power dissipation during short-circuit. A low dropout
voltage of 500mV is maintained when the input voltage
drops below the programmed output voltage, such as
during automotive cold crank.
An internally compensated current mode topology is used
for fast transient response and good loop stability. A high
efficiency 75mΩ switch is included on the die along with a
boost Schottky diode. An accurate 1.02V threshold enable
pin can be driven directly from a microcontroller or used
as a programmable undervoltage lockout. A capacitor on
the SS pin provides a controlled inrush current (soft-start).
A power good flag signals when V_OUT reaches 91.6% of
the programmed output voltage. The LT3976 is available
in small 16-lead MSOP and 24-lead 3mm × 5mm QFN
packages with exposed pad for low thermal resistance.
Typical Application
V_IN
4.3V TO 40V
3.3V Step-Down Converter
OFF ON
10µF
V_IN
EN
BOOST
PG
SW
LT3976
SS
RT
10nF
SYNC
130k
OUT
FB
GND
f = 400kHz
0.47µF
3.3µH
PDS540
2Ω
470pF
1M
10pF
576k
3976 TA01a
V_OUT
3.3V
5A
47µF
1210
×2
No-Load Supply Current
8
IN REGULATION
7
V_OUT = 3.3V
6
5
4
3
2
1
0
0 5 10 15 20 25 30 35 40
INPUT VOLTAGE (V)
3976 G05
For more information www.linear.com/3976
3976f
1