LM2744EVAL National Semiconductor, LM2744EVAL Datasheet
LM2744EVAL
Specifications of LM2744EVAL
Related parts for LM2744EVAL
LM2744EVAL Summary of contents
Page 1
... Typical Application © 2007 National Semiconductor Corporation Features ■ Power stage input voltage from 1V to 16V ■ ...
Page 2
Connection Diagram Ordering Information Order Number LM2744MTC LM2744MTCX Pin Descriptions BOOT (Pin 1) - Bootstrap pin. This is the supply rail for the high-side gate driver. When the high-side MOSFET turns on, the voltage on this pin should be at ...
Page 3
... Absolute Maximum Ratings If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications BOOT Voltage All other pins Junction Temperature Storage Temperature Soldering Information Lead Temperature (soldering, 10sec) Electrical Characteristics V = 3.3V unless otherwise indicated. Typicals and limits appearing in plain type apply for T CC boldface type apply over full Operating Temperature Range ...
Page 4
Symbol Parameter GATE DRIVE I BOOT Pin Quiescent Current Q-BOOT R High-Side MOSFET Driver Pull- HG_UP Up ON resistance R High-Side MOSFET Driver Pull- HG_DN Down ON resistance R Low-Side MOSFET Driver Pull- LG_UP Up ON resistance R Low-Side MOSFET ...
Page 5
Typical Performance Characteristics Efficiency (V = 1.2V, V OUT V = 3.3V 300kHz CC SW Efficiency (V = 3.3V, V OUT 300kHz Operating Current plus BOOT Current vs Frequency CC ...
Page 6
BOOT Pin Current vs Temperature for BOOT Voltage = 300kHz, FDS6898A FET, No-Load SW Frequency vs Temperature (F set to 600kHz nominal) SW Switch Waveforms (HG Rising 3.3V 5V REF ...
Page 7
Start-Up (No-Load 3.3V 5V 0.6V REF OUT C = 12nF 300kHz SS SW Shutdown (Full-Load 3.3V 5V 0.6V REF OUT ...
Page 8
Line Transient Response ( 3.3V 0.6V REF 300kHz OUT SW www.national.com = 3V to 7V) Line Transient Response ( 1.2V V OUT CC 20106054 ...
Page 9
Block Diagram Application Information THEORY OF OPERATION The LM2744 is a voltage-mode, high-speed synchronous buck regulator with a PWM control scheme designed for use in set-top boxes, thin clients, DSL/Cable modems, and other applications that require high efficiency ...
Page 10
Where and kΩ. SW FADJ TRACKING A VOLTAGE LEVEL The LM2744 can track the output of a master power supply during soft-start by connecting a resistor divider to the SS/ TRACK pin. In ...
Page 11
FIGURE 4. Sequencing Circuit A desired delay time t between the startup of the master DELAY supply output voltage and the LM2744 output voltage can be set based on the SD pin low-to-high threshold V slew rate of the voltage ...
Page 12
This bootstrap voltage is usually supplied from a local charge pump structure. But looking at the Typical Appli- cation schematic, this also means that the difference voltage which is the voltage the bootstrap capacitor ...
Page 13
LM2744 continues regardless of the state of the Power Good signal. The Power Good flag will return to logic high whenever the feedback pin voltage ...
Page 14
another voltage between 1. (see the Electrical Characteristics table). CC DESIGN CONSIDERATIONS The following is a design procedure for all the components needed to create the Typical Application Circuit shown on ...
Page 15
Losses in the high-side MOSFET can be broken down into conduction loss, gate charging loss, and switching loss. Con- duction loss, is approximately 1. DSON-HI (High-Side ...
Page 16
In the equation for f , the variable R DP sistance, and represents the inductor DCR plus the on resis- tance of the high-side MOSFET. R divided by output current. The power stage transfer function G is given by the ...
Page 17
One method to select use an iterative pro- EA cess beginning with these worst-case conditions. 1. Increase Check overall bandwidth and phase margin 3. Change V to minimum and recheck overall bandwidth IN ...
Page 18
As with the generic equation, G EA-ACTUAL take into account the limited bandwidth of the error amplifier. The result is: The total control loop transfer function H is equal to the power stage transfer function multiplied by the error amplifier ...
Page 19
There are few additional losses that are taken into account: IC Operating Loss (P IC Q_VCC CC where I is the typical operating V Q-VCC 1.5mA *3.3V = 4.95mW IC ...
Page 20
Example Circuits FIGURE 15 3.3V @ 2A, V PART PART NUMBER U LM2744 1 Q FDS6898A 1 D MBR0520LTI 1 L DO3316P-472 16SP100M 6SP220M VJ0805Y104KXXA BOOT ...
Page 21
FIGURE 16. 3.3V to 2.5V @ 2A, V PART PART NUMBER U LM2744 1 Q FDS6898A 1 D MBR0520LTI 1 L DO3316P-332 16SP100M 6SP220M VJ0805Y104KXXA BOOT ...
Page 22
Physical Dimensions www.national.com inches (millimeters) unless otherwise noted TSSOP-14 Pin Package NS Package Number MTC14 22 ...
Page 23
Notes 23 www.national.com ...
Page 24
... National Semiconductor and the National Semiconductor logo are registered trademarks of National Semiconductor Corporation. All other brand or product names may be trademarks or registered trademarks of their respective holders. ...