LM5642

·Two synchronous buck regulators
·180° out of phase operation
· Synchronizable switching frequency from 150kHz to 250kHz
· 4.5V to 36V input range
· 50µA Shutdown current
·Adjustable output from 1.3V to 90% of Vin
· 0.04% (typical) line and load regulation error
·Current mode control with or without a sense resistor
·Independent enable/soft-start pins allow simple sequential startup configuration.
·Configurable for single output parallel operation. (See Figure 2)
·Adjustable cycle-by-cycle current limit
· Input under-voltage lockout
·Output over-voltage latch protection
· Output under-voltage protection with delay
· Thermal shutdown
· Self discharge of output capacitors when the regulator is OFF
· TSSOP package

·Embedded Computer Systems
· Telecom Systems
· Set-Top Boxes
· WebPAD
· Point Of Load Power Architectures

Voltages from the indicated pins to SGND/PGND:
VIN, ILIM1, ILIM2, KS1, KS2 .......................................................................−0.3V to 38V
SW1, SW2, RSNS1, RSNS2 ...............................................................−0.3 to (VIN +0.3)V
FB1, FB2, VDD1, VDD2 ..................................................................................−0.3V to 6V
SYNC, COMP1, COMP2, UV Delay .................................................−0.3V to (VLIN5+0.3)V
ON/SS1, ON/SS2 (Note 2) ............................................................−0.3V to (VLIN5+0.6)V
CBOOT1, CBOOT2 ......................................................................................................43V
CBOOT1 to SW1, CBOOT2 to SW2 .................................................................−0.3V to 7V
LDRV1, LDRV2 ...................................................................................−0.3V to(VDD+0.3)V
HDRV1 to SW1, HDRV2 to SW2 ................................................................................−0.3V
HDRV1 to CBOOT1, HDRV2 toCBOOT2 ......................................................................+0.3V
Power Dissipation (T_A = 25°C),
(Note 3) ....................................................................................................................1.1W
Ambient Storage Temperature
Range .................................................................................................−65°C to +150°C
Soldering Dwell Time, Temperature
(Note 4)
Wave ...........................................................................................................4 sec, 260°C
Infrared ......................................................................................................10sec, 240°C
Vapor Phase ...............................................................................................75sec, 219°C
ESD Rating (Note 5) ....................................................................................................2kV

The LM5642 consists of two current mode synchronous
buck regulator controllers operating 180° out of phase with
each other at a normal switching frequency of 200kHz.
Out of phase operation reduces the input ripple RMS current,
thereby significantly reducing the required input capacitance.
The switching frequency can be synchronized to an external clock between 150kHz and 250kHz. The two switching regulator outputs can also be paralleled to operate as a dual-phase single output regulator.

The output of each channel can be independently adjusted from 1.3 to 90% of Vin. An internal 5V rail is also available externally for driving bootstrap circuitry. Current-mode feedback control assures excellent line and load regulation and a wide loop bandwidth for excellent response to fast load transients. Current is sensed across either the Vds of the top FET or across an external currentsense resistor connected in series with the drain of the top FET.

The LM5642 features analog soft-start circuitry that is independent of the output load and output capacitance making the soft-start behavior more predictable and controllable than traditional soft-start circuits. Over-voltage protection is available for both outputs. A UVDelay pin is also available to allow delayed shut off time for the IC during an output under-voltage event.