LT3988 Datasheet, PDF (1/24 Pages) Linear Technology – Dual 60V Step-Down Regulator

Features
n _{Wide Input Range:}
Operation from 4.1V to 60V
Overvoltage Lockout Protects Circuit Through
80V Transients
n _{Two 1A Output Switching Regulators with Internal}
Power Switches
n _{Short Circuit Robust}
n _{Adjustable 250kHz to 2.5MHz Switching Frequency,}
Synchronizable Over the Full Range
n _{Integrated Boost Diodes}
n _{Integrated Loop Compensation}
n _{Anti-Phase Switching Reduces Ripple}
n _{Low Shutdown IQ (<2µA)}
n _{Uses Small Inductors and Ceramic Capacitors}
n _{Thermally Enhanced, 16-Lead MSOP Package}
Applications
n _{Commercial Vehicle Battery Regulation}
n _{Industrial Supplies}
n _{Distributed Supply Regulation}
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LT3988
Dual 60V Monolithic 1A
Step-Down Switching
Regulator
Description
The LT^®3988 is a dual, current mode, step-down, DC/DC
converter that accepts two input voltages up to 60V (80V
transient), which may be driven from separate supplies or
can be cascaded. High efficiency switches are included on
the die along with internal boost diodes and loop compensa-
tion. Both converters are capable of generating 1A outputs,
are synchronized to a single oscillator programmable up
to 2.5MHz, and run with opposite phases, reducing input
ripple current.
The switching frequency is set with a single resistor yield-
ing a range of 250kHz to 2.5MHz, or a clock signal can
be applied to the SYNC pin. The LT3988’s high switching
frequency allows the use of small inductors and capacitors,
resulting in a very small dual output supply. The constant
switching frequency, combined with low impedance ce-
ramic capacitors, results in low, predictable output ripple.
A current mode PWM architecture provides fast transient
response with cycle-by-cycle current limiting. Diode current
sense and thermal shutdown provide additional protection.
The LT3988 is available in a 16-lead MSOP package with
an exposed pad for low thermal resistance.
Typical Application
V_IN
7V TO 60V
TRANSIENT
TO 80V
V_OUT1
5V, 1A
22µH
4.7µF
1000pF
0.22µF
V_IN1
V_IN2
EN/UVLO TRACK/SS2
TRACK/SS1
LT3988
RT
SYNC
BD
BOOST1
BOOST2
SW1
SW2
200k
0.22µF
1000pF
15µH
V_OUT2
3.3V, 1A
57.6k
DA1
DA2
34k
FB1
FB2
GND
47µF
10.2k
10k
47µF
22pF
3988 TA01
Efficiency
90
V_OUT = 5V
85
80
V_OUT = 3.3V
75
70
65
60
55
V_IN = 12V
50
f_SW = 500kHz
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
I_OUT (A)
3988 TA01b
3988f
1