August 31, 2010
LM26420
Dual 2.0A, High Frequency Synchronous Step-Down DC-
DC Regulator
General Description
Features
The LM26420 regulator is a monolithic, high frequency, dual
PWM step-down DC/DC converter in a 16 Pin LLP and a 20
Pin eTSSOP package. It provides all the active functions to
provide local DC/DC conversion with fast transient response
and accurate regulation in the smallest possible PCB area.
With a minimum of external components, the LM26420 is
easy to use. The ability to drive two 2.0A loads with an internal
75 mΩ PMOS top switch and an internal 50 mΩ NMOS bottom
switch using state-of-the-art 0.5 µm BiCMOS technology re-
sults in the best power density available. The world-class
control circuitry allows on-times as low as 30ns, thus sup-
porting exceptionally high frequency conversion over the en-
tire 3V to 5.5V input operating range down to the minimum
output voltage of 0.8V. Switching frequency is internally set
to 550 kHz or 2.2 MHz, allowing the use of extremely small
surface mount inductors and chip capacitors. Even though the
operating frequency is high, efficiencies up to 93% are easy
to achieve. External shutdown is included, featuring an ultra-
low stand-by current. The LM26420 utilizes current-mode
control and internal compensation to provide high-perfor-
mance regulation over a wide range of operating conditions.
Additional features include internal soft-start circuitry to re-
duce inrush current, pulse-by-pulse current limit, thermal
shutdown, power good indicators, precision enables, and out-
put over-voltage protection.
Input voltage range of 3.0V to 5.5V
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Output voltage range of 0.8V to 4.5V
2.0A output current per output
High Switching Frequencies
2.2MHz (LM26420X)
0.55MHz (LM26420Y)
75mΩ PMOS switch
50mΩ NMOS switch
0.8V, 1.5% Internal Voltage Reference
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Internal soft-start
Independent power good for each output
Independent precision enable for each output
Current mode, PWM operation
Thermal Shutdown
Over voltage protection
Start-up into Pre-biased Output Loads
Outputs are 180° out of phase
Applications
Local 5V to Vcore Step-Down Converters
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Core Power in HDDs
Set-Top Boxes
USB Powered Devices
DSL Modems
Powering Core and I/O voltages for FPGAs, CPLDs, and
ASICs
Typical Application Circuit
30069664
30069684
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