LTC1624
High Efficiency SO-8
N-Channel Switching
Regulator Controller
FEATURES DESCRIPTION
n
N-Channel MOSFET Drive The LTC 1624 is a current mode switching regulator
n
Implements Boost, Step-Down, SEPIC controller that drives an external N-channel power MOSFET
and Inverting Regulators using a fixed frequency architecture. It can be operated in
n
Wide V Range: 3.5V to 36V Operation all standard switching configurations including boost,
IN
TM
n
Wide V Range: 1.19V to 30V in Step-Down step-down, inverting and SEPIC. Burst Mode operation
OUT
Configuration provides high efficiency at low load currents. A maximum
n
1% 1.19V Reference high duty cycle limit of 95% provides low dropout operation
n
Low Dropout Operation: 95% Duty Cycle which extends operating time in battery-operated systems.
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200kHz Fixed Frequency
The operating frequency is internally set to 200kHz, allowing
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Low Standby Current
small inductor values and minimizing PC board space. The
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Very High Efficiency
operating current level is user-programmable via an external
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Remote Output Voltage Sense
current sense resistor. Wide input supply range allows
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Logic-Controlled Micropower Shutdown
operation from 3.5V to 36V (absolute maximum).
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Internal Diode for Bootstrapped Gate Drive
n A multifunction pin (I /RUN) allows external
Current Mode Operation for Excellent Line and TH
compensation for optimum load step response plus
Load Transient Response
n shutdown. Soft start can also be implemented with the
Available in an 8-Lead SO Package
I /RUN pin to properly sequence supplies.
TH
U
APPLICATIONS
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Notebook and Palmtop Computers, PDAs
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Cellular Telephones and Wireless Modems
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Battery-Operated Digital Devices
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DC Power Distribution Systems
, LTC and LT are registered trademarks of Linear Technology Corporation.
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Battery Chargers Burst Mode is a trademark of Linear Technology Corporation.
TYPICAL APPLICATION
V
IN
4.8V TO 28V
1000pF
SENSE
V
IN
C
IN
+
R
22F
SENSE
0.05
35V
I /RUN
BOOST
TH
2
C
C
M1
LTC1624
470pF
Si4412DY
V
TG
FB
R
C
L1
C
B
6.8k 100pF
10H
0.1F V
OUT
GND
SW 3.3V
D1
2A
MBRS340T3 R2
C
35.7k
OUT
+
100F
10V
R1
2
20k
1624 F01
Figure 1. High Efficiency Step-Down Converter
1
U
ULTC1624
ABSOLUTE MAXIMUM RATINGS PACKAGE/ORDER INFORMATION
Input Supply Voltage (V ).........................36V to 0.3V
IN
ORDER PART
Topside Driver Supply Voltage (BOOST)....42V to 0.3V
TOP VIEW
NUMBER
Switch Voltage (SW)..................................36V to 0.6V
SENSE
1
8
V
IN
Differential Boost Voltage
I /RUN
2
7
BOOST
TH
LTC1624CS8
(BOOST to SW) ....................................7.8V to 0.3V
V
3
6
TG
FB LTC1624IS8
SENSE Voltage
GND 4 5 SW
V < 15V.................................. (V + 0.3V) to 0.3V
IN IN
S8 PACKAGE
S8 PART MARKING
V 15V .......................... (V +0.3V) to (V 15V)
IN IN IN
8-LEAD PLASTIC SO
I /RUN, V Voltages ............................ 2.7V to 0.3V
TH FB
1624
T = 125C, = 110C/ W
Peak Driver Output Current < 10s (TG) .................... 2A JMAX JA
1624I
Operating Temperature Range
LTC1624CS ............................................ 0C to 70C
Consult factory for Military grade parts.
LTC1624IS......................................... 40C to 85C
Junction Temperature (Note 1)............................. 125C
Storage Temperature Range ................. 65C to 150C
Lead Temperature (Soldering, 10 sec).................. 300C
T = 25C, V = 15V, unless otherwise noted.
ELECTRICAL CHARACTERISTICS
A IN
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
Main Control Loop
I V Feedback Current (Note 2) 10 50 nA
IN FB
V Feedback Voltage (Note 2) l 1.1781 1.19 1.2019 V
FB
V Reference Voltage Line Regulation V = 3.6V to 20V (Note 2) 0.002 0.01 %/V
LINE REG IN
V Output Voltage Load Regulation (Note 2)
LOAD REG
I Sinking 5A l 0.5 0.8 %
TH
I Sourcing 5A l 0.5 0.8 %
TH
V Output Overvoltage Lockout 1.24 1.28 1.32 V
OVL
I Input DC Supply Current (Note 3)
Q
Normal Mode 550 900 A
Shutdown V = 0V 16 30 A
ITH/RUN
V Run Threshold 0.6 0.8 V
ITH/RUN
I Run Current Source V = 0.3V 0.8 2.5 5.0 A
ITH/RUN ITH/RUN
Run Pullup Current V = 1V 50 160 350 A
ITH/RUN
V Maximum Current Sense Threshold V = 1.0V 145 160 185 mV
SENSE(MAX) FB
TG Transition Time
TG t Rise Time C = 3000pF 50 150 ns
r LOAD
TG t Fall Time C = 3000pF 50 150 ns
f LOAD
f Oscillator Frequency l 175 200 225 kHz
OSC
V Boost Voltage SW = 0V, I = 5mA, V = 8V 4.8 5.15 5.5 V
BOOST BOOST IN
V Boost Load Regulation SW = 0V, I = 2mA to 20mA 3 5 %
BOOST BOOST
The l denotes specifications which apply over the full operating T = T + (P 110C/W)
J A D
temperature range.
Note 2: The LTC1624 is tested in a feedback loop which servos V to
FB
LTC1624CS: 0C T 70C the midpoint for the error amplifier (V = 1.8V).
A ITH
LTC1624IS: 40C T 85C
A Note 3: Dynamic supply current is higher due to the gate charge being
Note 1: T is calculated from the ambient temperature T and power delivered at the switching frequency. See Applications Information.
J A
dissipation P according to the following formula:
D
2
U W U W
U WW