LT3980
1
3980fa
For more information www.linear.com/LT3980
58V, 2A, 2.4MHz
Step-Down Switching Regulator
with 85µA Quiescent Current
The LT
®
3980 is an adjustable frequency (100kHz to
2.4MHz) monolithic buck switching regulator that accepts
input voltages up to 58V (80V transient). A high efficiency
200mΩ switch is included on the die along with a boost
Schottky diode and the necessary oscillator, control, and
logic circuitry. Current mode topology is used for fast
transient response and good loop stability. Catch diode
current sense (DA pin) protects the circuit during input
voltage transients even when a high switching frequency
is used. Low ripple Burst Mode operation maintains high
efficiency at low output currents while keeping output
ripple below 15mV in a typical application. In addition, the
LT3980 can further enhance low output current efficiency
by drawing bias current from the output when V
OUT
is
above 3V. Shutdown reduces input supply current to less
than 1µA while a resistor and capacitor on the RUN/SS
pin provide a controlled output voltage ramp (soft-start).
A power good flag signals when V
OUT
reaches 91% of
the programmed output voltage. The LT3980 is available
in 16-pin MSOP and 3mm × 4mm DFN packages with
exposed pads for low thermal resistance.
■
Automotive Battery Regulation
■
Distributed Supply Regulation
■
Industrial Supplies
■
Wall Transformer Regulation
■
Wide Input Range: Operation from 3.6V to 58V
■
Overvoltage Lockout Protects Circuits Through 80V
Transients
■
2A Maximum Output Current
■
Low Ripple (<15mV
P-P
) Burst Mode
®
Operation:
I
Q
= 85µA at 12V
IN
to 3.3V
OUT
■
Adjustable Switching Frequency: 100kHz to 2.4MHz
■
Low Shutdown Current: I
Q
< 1µA
■
Catch Diode Current Sense Protects Circuit Through
Short-Circuit and Input Overvoltage
■
Synchronizable Between 250kHz to 2MHz
■
Power Good Flag
■
Saturating Switch Design: 200mΩ On-Resistance
■
Thermal Protection
■
Soft-Start Capability
■
Small 16-Pin Thermally Enhanced MSOP and
3mm × 4mm DFN Packages
5V Step-Down Converter Efficiency, V
OUT
= 5V
Typical applicaTion
DescripTion
FeaTures
applicaTions
SW
FB
V
C
PG
RT
V
IN
BD
V
IN
6.5V TO 58V
TRANSIENT
TO 80V
OUT
5V
2A
10µF
0.47µF
1nF
47µF
100k
4.75k
97.6k
10µH
22pF
536k
GND
DA
OFF ON
LT3980
3980 TA01
RUN/SS BOOST
SYNC
L, LT, LTC, LTM, Linear Technology, Burst Mode and the Linear logo are registered trademarks
of Linear Technology Corporation. All other trademarks are the property of their respective
owners.
I
LOAD
(A)
0 0.5
EFFICIENCY (%)
1
2
1.5
V
IN
= 12V
V
IN
= 48V
f = 400kHz
D = DIODES, INC. SBR3U100LP
V
IN
= 24V
85
70
60
55
50
95
90
80
75
65