LM5642MH NSC [National Semiconductor], LM5642MH Datasheet

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LM5642MH

Manufacturer Part Number
LM5642MH
Description
High Voltage, Dual Synchronous Buck Converter with Oscillator Synchronization
Manufacturer
NSC [National Semiconductor]
Datasheet

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© 2007 National Semiconductor Corporation
LM5642/LM5642X
High Voltage, Dual Synchronous Buck Converter with
Oscillator Synchronization
General Description
The LM5642 series consists of two current mode syn-
chronous buck regulator controllers operating 180° out of
phase with each other at a normal switching frequency of
200kHz for the LM5642 and at 375kHz for the LM5642X.
Out of phase operation reduces the input RMS ripple current,
thereby significantly reducing the required input capacitance.
The switching frequency can be synchronized to an external
clock between 150kHz and 250kHz for the LM5642 and be-
tween 200 kHz and 500 kHz for the LM5642X. 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 1.3V 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 wide loop bandwidth for excellent re-
sponse to fast load transients. Current is sensed across either
the Vds of the top FET or across an external current-sense
resistor connected in series with the drain of the top FET.
The LM5642 features analog soft-start circuitry that is inde-
pendent of the output load and output capacitance making the
soft-start behavior more predictable and controllable than tra-
ditional soft-start circuits.
Over-voltage protection is available for both outputs. A UV-
Delay pin is also available to allow delayed shut off time for
the IC during an output under-voltage event.
Typical Application Circuit
200601
Features
Applications
Two synchronous buck regulators
180° out of phase operation
200kHz fixed nominal frequency: LM5642
375kHz fixed nominal frequency: LM5642X
Synchronizable switching frequency from 150kHz to
250kHz for the LM5642 and 200kHz to 500kHz for the
LM5642X
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 accuracy
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 and eTSSOP (Exposed PAD) packages
Embedded Computer Systems
Navigation Systems
Telecom Systems
Set-Top Boxes
WebPAD
Point Of Load Power Architectures
20060101
www.national.com
June 2007

Related parts for LM5642MH

LM5642MH Summary of contents

Page 1

LM5642/LM5642X High Voltage, Dual Synchronous Buck Converter with Oscillator Synchronization General Description The LM5642 series consists of two current mode syn- chronous buck regulator controllers operating 180° out of phase with each other at a normal switching frequency of 200kHz ...

Page 2

... Connection Diagrams Top View Ordering Information Order Number Package Type LM5642MH 28-Lead eTSSOP LM5642MHX LM5642MTC 28-Lead TSSOP LM5642MTCX Pin Descriptions KS1 (Pin 1): The positive (+) Kelvin sense for the internal current sense amplifier of Channel 1. Use a separate trace to connect this pin to the current-sense point. It should be con- nected to VIN as close as possible to the current-sense resistor ...

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RSNS2 (Pin 15): The negative (-) Kelvin sense for the internal current sense amplifier of Channel 2. Connect this pin to the low side of the current sense resistor that is placed between VIN and the drain of the top ...

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Absolute Maximum Ratings If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. Voltages from the indicated pins to SGND/PGND: VIN, ILIM1, ILIM2, KS1, KS2 SW1, SW2, RSNS1, RSNS2 FB1, FB2, VDD1, ...

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Symbol Parameter V V Overvoltage OVP OUT Shutdown Latch Threshold S SW1, SW2 ON-Resistance V wx_R Gate Drive I CBOOTx Leakage Current V CBOOT I HDRVx and LDRVx Source SC_DRV Current I HDRVx Sink Current sk_HDRV I LDRVx Sink Current ...

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Note 1: Absolute maximum ratings indicate limits beyond which damage to the device may occur. Operating Range indicates conditions for which the device is intended to be functional, but does not guarantee specfic performance limits. For guaranteed specifications and test ...

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FIGURE 1. Typical 2 Channel Application Circuit 7 20060103 www.national.com ...

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FIGURE 2. Typical Single Channel Application Circuit 8 20060104 ...

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9 www.national.com ...

Page 10

Typical Performance Characteristics Softstart Waveforms (No-Load Both Channels) Over-Current and UVP Shutdown (VIN = 24V, Io2 = 0A) Ch.1 Load Transient Response (VIN = 24V, Vo1 = 1.8V) www.national.com UVP Startup Waveform (VIN = 24V) 20060123 20060120 Ch.2 Load Transient ...

Page 11

Ch. 2 Load Transient Response (VIN = 36V, Vo2 = 3.3V) 20060128 Input Supply Current vs Temperature (Shutdown Mode V = 28V) IN 20060124 VLIN5 vs Temperature 20060126 Ch.1 Load Transient Response (VIN = 36V, Vo1 = 1.8V) Input Supply ...

Page 12

FB Reference Voltage vs Temperature Error Amplifier Tranconductance Gain vs Temperature Efficiency vs Load Current Ch.2 = 3.3V, Ch.1 = Off www.national.com Operating Frequency vs Temperature 20060166 Efficiency vs Load Current Using Resistor Sense Ch.1 = 1.8V, Ch.2 = Off ...

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Efficiency vs Load Current Using Vds Sense Ch.2 = 3.3V, Ch.1 = Off 13 20060173 www.national.com ...

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Operating Descriptions SOFT START The ON/SS1 pin has dual functionality as both channel enable and soft start control. Referring to the soft start block diagram is shown in Figure 3, the LM5642 will remain in shutdown mode while both soft ...

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UNDER VOLTAGE PROTECTION (UVP) AND UV DELAY If the output voltage on either channel falls below 80% of nominal, under voltage protection activates. As shown in Fig- ure 5, an under-voltage event will shut off the UV_DELAY MOSFET, which will ...

Page 16

Imax is the maximum expected load current, including overload multiplier (ie:120%), and Irip is the inductor ripple current (See Equation 17). The above equation gives the maximum allowable value for Rsns. Conduction losses will increase with larger Rsns, thus ...

Page 17

As shown in Input Capacitor Selection section, when the duty cycle D1 for Chan- nel 1 overlaps the duty cycle D2 for Channel 2, the input rms current increases, requiring more ...

Page 18

FIGURE 10. Output Voltage Range Output Capacitor Selection In applications that exhibit large, fast load current swings, the slew rate of such a load current transient will likely be beyond the response speed of the regulator. Therefore, to meet volt- ...

Page 19

Since inductor ripple current is often the criterion for selecting an output inductor good idea to double-check this value. The equation is: Also important is the ripple content, which is defined by Irip / Inom. Generally speaking, ...

Page 20

Tj_max is the maximum allowed junction temperature in the FET, Ta_max is the maximum ambient temperature the junction-to-ambient thermal resistance of the FET, θja and TC is the temperature coefficient of the on-resistance which is typically in ...

Page 21

The control-output corner frequencies, and thus the desired compensation corner frequencies, can be determined ap- proximately by the following equations: Since fp is determined by the output network, it will shift with loading (Ro best to use a ...

Page 22

If high switching currents must be routed through vias and/or internal planes, use multiple vias in parallel to reduce their resistance and inductance. The power components www.national.com should be kept close ...

Page 23

Bill Of Materials for Figure 1 24V to 1.8, 3.3V LM5642 ID Part Number U1 LM5642 Q1, Q4 Si4850EY Q2, Q5 Si4840DY D3 BAS40-06 L1 RLF12560T-4R2N100 L2 RLF12545T-100M5R1 C1 C3216X7R1H105K C3, C4, C14, VJ1206Y101KXXAT C15 C27 C2012X5R1C105K C6, C16 C5750X5R1H106M ...

Page 24

Bill of Materials for Figure 2 30V to 1.8V, 20A LM5642 ID Part Number U1 LM5642 Q1, Q4 Si4850EY Q2, Q3, Q5, Q6 Si4470DY D3 BAS40-06 L1,L2 RLF12560T-2R7N110 C1 C3216X7R1H105K C10, C24, C27 C2012X5R1C105K C6, C16, C28, C5750X5R1H106M C30 C9, ...

Page 25

Bill Of Materials Based on Figure Part Number U1 LM5642X Q1, Q4 Si4850EY Q2, Q5 Si4840DY D3 BA54A L1, L2 RLF12545T-4R2N100 C1 C3216X7R1H105K C3, C4, C14, VJ1206Y101KXXAT C15 C27 C2012X5R1C105K C6, C28 C5750X7R1H106M C9, C23 C4532X7R0J107M C2, ...

Page 26

Bill Of Materials Based on Figure Part Number U1 LM5642X Q1, Q4 Si4850EY Q2, Q5 Si4840DY D3 BA54A L1, L2 RLF12545T-5R6N6R1 C1 C3216X7R1H105K C3, C4, C14, VJ1206Y101KXXAT C15 C27 C2012X5R1C105K C6, C28 C5750X7R1H106M C9, C23 C4532X7R0J107M C2, ...

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... Physical Dimensions inches (millimeters) unless otherwise noted 28-Lead TSSOP Package Order Number LM5642MTC, LM5642XMT NS Package Number MTC28 28-Lead eTSSOP Package Order Number LM5642MH, LM5642XMH NS Package Number MXA28A 27 www.national.com ...

Page 28

THE CONTENTS OF THIS DOCUMENT ARE PROVIDED IN CONNECTION WITH NATIONAL SEMICONDUCTOR CORPORATION (“NATIONAL”) PRODUCTS. NATIONAL MAKES NO REPRESENTATIONS OR WARRANTIES WITH RESPECT TO THE ACCURACY OR COMPLETENESS OF THE CONTENTS OF THIS PUBLICATION AND RESERVES THE RIGHT TO MAKE ...

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