LM5088MH-1 NSC [National Semiconductor], LM5088MH-1 Datasheet
LM5088MH-1
Available stocks
Related parts for LM5088MH-1
LM5088MH-1 Summary of contents
Page 1
Wide Input Range Non-Synchronous Buck Controller General Description The LM5088 high voltage non-synchronous buck controller features all the necessary functions to implement an efficient high voltage buck converter using a minimum number of ex- ternal components. The LM5088 can be ...
Page 2
... Connection Diagrams Top View (Dither version) LM5088-1 Ordering Information Order Number LM5088MH-1 LM5088MHX-1 LM5088MH-2 LM5088MHX-2 Pin Descriptions Pin(S) Name Description 1 VIN Input supply voltage 2 EN Enable input 3 SS Soft-start 4 RAMP Ramp control signal www.national.com 30083902 Description NSC Package Drawing TSSOP-16EP, Dithering ...
Page 3
Pin(S) Name Description 5 RT/SYNC Internal oscillator frequency set input and synchronization input 6 GND Ground 7 COMP Output of the internal error amplifier 8 FB Feedback signal from the regulated output 9 OUT Output voltage connection Connect directly to ...
Page 4
Absolute Maximum Ratings If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. VIN, VOUT to GND BOOT to GND SW to GND VCC to GND GND ...
Page 5
Symbol Parameter OSCILLATOR (RT Pin) F Nominal Oscillator Frequency nom1 F nom2 F Dithering Range min F max SYNC SYNC positive threshold SYNC Pulse Width CURRENT LIMIT V Cycle by cycle sense voltage threshold V CS(TH) Cycle by Cycle Current ...
Page 6
Typical Performance Characteristics Typical Application Circuit Efficiency VCC VCC Frequency vs R www.national.com 30083940 30083942 RT 30083944 30083941 Shutdown Current 30083943 Frequency vs V VCC 30083945 ...
Page 7
V vs Temperature FB 30083946 Soft-Start vs Temperature 30083948 Frequency vs Temperature 30083950 Forced-Off Time vs Temperature Current-Limit vs Temperature Error Amplifier Gain/Phase 7 30083947 30083949 30083951 www.national.com ...
Page 8
Block Diagram www.national.com FIGURE 1. Block Diagram 8 30083904 ...
Page 9
Detailed Operation The LM5088 Wide Input Range Buck Controller features all the functions necessary to implement an efficient high voltage step-down converter using a minimum number of external components. The control method is based on peak current mode control utilizing ...
Page 10
Error Amplifier and PWM Comparator The internal high gain error amplifier generates an error signal proportional to the difference between the regulated output voltage and an internal precision voltage reference (1.205V). The output of the error amplifier is connected to ...
Page 11
FIGURE 3. Composition of Current Sense Signal The sample & hold DC level illustrated in Figure 3 is derived from a measurement of the re-circulating (or free-wheeling) diode current. The diode current flows through the current sense resistor connected between ...
Page 12
Where 1/f and T is the forced off-time (280 OSC SW OFF (max) ns typical, 365 ns maximum); f and T SW frequency and oscillator period, respectively. From the above equation, it can be seen that for a ...
Page 13
FIGURE 6. Conducted Emissions Measured at the Input of a LM5088 Based Buck Converter Figure 6 shows the conducted emissions on the LM5088 evaluation board input power line. It can be seen from the above picture that, the peak emissions ...
Page 14
FET when it is turned ON, if the V exceeds 1.5V, the comparator turns off the buck DS FET immediately. This feature will help protect the buck FET in catastrophic conditions such ...
Page 15
FIGURE 8. Current Limit Restart Timing Diagram Soft-Start The soft-start (SS) feature forces the output to rise linearly until it reaches the steady-state operating voltage set by the feedback resistors. The LM5088 will regulate the FB pin to the SS ...
Page 16
The maximum ripple current occurs at the maximum input voltage. Typically selected between 20% and 40 the full load current. Higher ripple current will result in a small- er inductor. However, it places more burden on ...
Page 17
FIGURE 10. Additional Slope Compensation for VOUT > 5V OUTPUT CAPACITORS The output capacitors smooth the inductor current ripple and provide a source of charge for load transient conditions. The output capacitor selection is primarily dictated by the following ...
Page 18
OUTPUT VOLTAGE DIVIDER R and R set the output voltage level, the ratio of these FB1 FB2 resistors can be calculated from: 1.62 kΩ was chosen for R in this design which results in a FB1 R value of 5.11 ...
Page 19
ERROR AMPLIFIER COMPENSATION and C configure the error amplifier gain COMP COMP HF characteristics to accomplish a stable voltage loop gain. One advantage of current mode control is the ability of to close the loop with only ...
Page 20
PCB BOARD LAYOUT AND THERMAL CONSIDERATIONS In a buck regulator there are two loops where currents are switched very fast. The first loop starts from the input capac- itors, through the buck MOSFET, to the inductor then out to the ...
Page 21
21 www.national.com ...
Page 22
www.national.com 22 ...
Page 23
Bill of Materials for LM5088-1 and LM5088-2 Evaluation Boards Part Value Package C1,C2,C3,C4, 2.2µF C1210 C5 C6,C19 0.1µF C0805 C7 1µF C0603 C8,C11 100pF C0603 C9 270pF C0603 C13 0.1µF C0603 C10 0.022µF C0603 C12 0.015µF C0603 C15 470µF 0.327x0.327x0. ...
Page 24
Part Value R10 NU J1,J2,J3,J4 Terminal_Turret TP1,TP2 Slotted test point U1 PWM IC TSSOP16_EP www.national.com Package Manufacturer Manufacturer Part Number Description R0603 NU Keystone Keystone National 1509 Terminal, Turret 1040 Terminal test point slotted LM5088-1/LM5088-2 ECM Buck ...
Page 25
Physical Dimensions inches (millimeters) unless otherwise noted 16-Lead TSSOP-EP Package NS Package Number MXA16A 25 www.national.com ...
Page 26
For more National Semiconductor product information and proven design tools, visit the following Web sites at: Products Amplifiers www.national.com/amplifiers Audio www.national.com/audio Clock and Timing www.national.com/timing Data Converters www.national.com/adc Interface www.national.com/interface LVDS www.national.com/lvds Power Management www.national.com/power Switching Regulators www.national.com/switchers LDOs www.national.com/ldo ...