LM25010_08 NSC | Alldatasheet

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Technical content

Features

■ Wide 6V to 42V Input Voltage Range ■ Valley Current Limiting At 1.25A ■ Programmable Switching Frequency Up To 1 MHz ■ Integrated N-Channel Buck Switch ■ Integrated High Voltage Bias Regulator ■ No Loop Compensation Required ■ Ultra-Fast Transient Response ■ Nearly Constant Operating Frequency With Line and Load Variations ■ Adjustable Output Voltage ■ 2.5V, ±2% Feedback Reference ■ Programmable Soft-Start ■ Thermal shutdown ■ LM25010Q is AEC-Q100 Grade 1 & 0 qualified Typical Applications ■ Non-Isolated Telecommunications Regulator ■ Secondary Side Post Regulator ■ Automotive Electronics Package ■ LLP-10 (4 mm x 4 mm) ■ TSSOP-14EP ■ Both Packages Have Exposed Thermal Pad For Improved Heat Dissipation Basic Step-Down Regulator 20172743 © 2008 National Semiconductor Corporation 201727 www.national.com LM25010/LM25010Q 42V, 1.0A Step-Down Switching Regulator

Ordering Information

Order Number Package Type NSC Package Drawing Supplied As Automotve Grade* LM25010SD LLP-10 (4x4) SDC10A 1000 Units on Tape and Reel No LM25010SDX LLP-10 (4x4) SDC10A 4500 Units on Tape and Reel No LM25010MH TSSOP-14EP MXA14A 94 Units in Rail No LM25010MHX TSSOP-14EP MXA14A 2500 Units on Tape and Reel No LM25010Q1MH TSSOP-14EP MXA14A 94 Units in Rail Grade 1 LM25010Q1MHX TSSOP-14EP MXA14A 2500 Units on Tape and Reel Grade 1 LM25010Q0MH TSSOP-14EP MXA14A 94 Units in Rail Grade 0 LM25010Q0MHX TSSOP-14EP MXA14A 2500 Units on Tape and Reel Grade 0 *Automotive Grade (Q) product incorporates enhanced manufacturing and support processes for the automotive market, including defect detection methodologies. Reliability qualification is compliant with the requirements and temperature grades defined in the AEC-Q100 standard. Automotive grade products are identified with the letter Q. For more information go to http://www.national.com/automotive. www.national.com 2 LM25010/LM25010Q

Pin Number Name Description Application Information LLP-10 TSSOP-14 1 2 SW Switching Node Internally connected to the buck switch source. Connect to the inductor, free-wheeling diode, and bootstrap capacitor. 2 3 BST Boost pin for bootstrap capacitor Connect a capacitor from SW to the BST pin. The capacitor is charged from VCC via an internal diode during the buck switch off-time. 3 4 ISEN Current sense During the buck switch off-time, the inductor current flows through the internal sense resistor, and out of the ISEN pin to the free-wheeling diode. The current limit comparator keeps the buck switch off if the ISEN current exceeds 1.25A (typical). 4 5 SGND Current Sense Ground Re-circulating current flows into this pin to the current sense resistor. 5 6 RTN Circuit Ground Ground return for all internal circuitry other than the current sense resistor. 6 9 FB Voltage feedback input from the regulated output Input to both the regulation and over-voltage comparators. The FB pin regulation level is 2.5V. 7 10 SS Softstart An internal 11.5 µA current source charges the SS pin capacitor to 2.5V to soft-start the reference input of the regulation comparator. 8 11 RON/SD On-time control and shutdown An external resistor from VIN to the RON/SD pin sets the buck switch on-time. Grounding this pin shuts down the regulator. 9 12 VCC Output of the bias regulator The voltage at VCC is nominally equal to VIN for VIN < 8.9V, and regulated at 7V for VIN > 8.9V. Connect a 0.47 µF, or larger capacitor from VCC to ground, as close as possible to the pins. An external voltage can be applied to this pin to reduce internal dissipation if VIN is greater than 8.9V. MOSFET body diodes clamp VCC to VIN if VCC > VIN. 10 13 VIN Input supply voltage Nominal input range is 6V to 42V. Input bypass capacitors should be located as close as possible to the VIN pin and RTN pins. 1,7,8,14 NC No connection. No internal connection. Can be connected to ground plane to improve heat dissipation. EP Exposed Pad Exposed metal pad on the underside of the device. It is recommended to connect this pad to the PC board ground plane to aid in heat dissipation. 3 www.national.com LM25010/LM25010Q

Absolute Maximum Ratings (Note 1) If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. VIN to RTN -0.3V to 45V BST to RTN -0.3V to 59V SW to RTN (Steady State) -1.5V BST to VCC 45V BST to SW 14V VCC to RTN -0.3V to 14V SGND to RTN -0.3V to +0.3V SS to RTN -0.3V to 4V VIN to SW 45V All Other Inputs to RTN -0.3V to 7V ESD Rating (Note 2) Human Body Model 2kV Storage Temperature Range -65°C to +150°C Lead Temperature (Soldering 4 sec) (Note 4) 260°C Operating Ratings (Note 1) VIN Voltage 6.0V to 42V Junction Temperature LM25010/LM25010Q1 −40°C to + 125°C LM25010Q0 −40°C to + 150°C Electrical Charateristics Specifications with standard type are for TJ = 25°C only; limits in boldface type apply over the full Operating Junction Temperature (TJ) range. Minimum and Maximum limits are guaranteed through test, design, or statistical correlation. Typical values represent the most likely parametric norm at TJ = 25°C, and are provided for reference purposes only. Unless otherwise stated the following conditions apply: VIN = 24V, RON = 200kΩ. See (Note 5). Symbol Parameter Conditions Min Typ Max Units VCC Regulator VCCReg VCC regulated output 6.6 7 7.4 Volts VIN - VCC ICC = 0 mA, FS ≤ 200 kHz, 6.0V ≤ VIN ≤ 8.5V 100 mV VCC Bypass Threshold VIN Increasing 8.9 V VCC Bypass Hysteresis VIN Decreasing 260 mV VCC output impedance (0 mA ≤ ICC ≤ 5 mA) VIN = 6.0V 55 Ω VIN = 8.0V 50 VIN = 24V 0.21 VCC current limit (Note 3) VIN = 24V, VCC = 0V 15 mA UVLOVcc VCC under-voltage lock-out threshold VCC Increasing 5.25 V UVLOVCC hysteresis VCC Decreasing 180 mV UVLOVCC filter delay 100 mV overdrive 3 µs IIN operating current Non-switching, FB = 3V 645 920 µA IIN shutdown current RON/SD = 0V 90 170 µA Switch Characteristics RDS(on) Buck Switch RDS(on) @ fSW = 200 mA TJ ≤ 125°C TJ ≤ 150°C 0.35 0.80 0.85 Ω UVLOGD Gate Drive UVLO VBST - VSW Increasing 1.7 3.0 4.0 V UVLOGD hysteresis 400 mV SOFT-START Pin ISS Internal current source 8.0 11.5 15 µA Current Limit ILIM Threshold Current out of ISEN 1 1.25 1.5 A Resistance from ISEN to SGND 130 mΩ Response time 150 ns On Timer, RON/SD Pin tON - 1 On-time VIN = 10V, RON = 200 kΩ 2.1 2.75 3.4 µs tON - 2 On-time VIN = 42V, RON = 200 kΩ 500 695 890 ns Shutdown threshold Voltage at RON/SD rising 0.30 0.7 1.05 V Threshold hysteresis 40 mV www.national.com 4 LM25010/LM25010Q

Symbol Parameter Conditions Min Typ Max Units Off Timer tOFF Minimum Off-time 260 ns Regulation and Over-Voltage Comparators (FB Pin) VREF FB regulation threshold TJ ≤ 125°C TJ ≤ 150°C 2.445 2.435 2.50 2.550 V FB over-voltage threshold 2.9 V FB bias current 1 nA Thermal Shutdown TSD Thermal shutdown temperature 175 °C Thermal shutdown hysteresis 20 °C Thermal Resistance θJA Junction to Ambient, 0 LFPM Air Flow °C/W θJC Junction to Case SDC Package 5.2 5.2 °C/W Note 1: Absolute Maximum Ratings are limits beyond which damage to the device may occur. Operating Ratings are conditions under which operation of the device is intended to be functional. For guaranteed specifications and test conditions, see the Electrical Characteristics. Note 2: The human body model is a 100pF capacitor discharged through a 1.5kΩ resistor into each pin. Note 3: VCC provides bias for the internal gate drive and control circuits. Device thermal limitations limit external loading. Note 4: For detailed information on soldering plastic TSSOP and LLP packages refer to the Packaging Data Book available from National Semiconductor Corporation. Note 5: Typical specifications represent the most likely parametric norm at 25°C operation. 5 www.national.com LM25010/LM25010Q

Typical Performance Characteristics VCC vs VIN 20172704 VCC vs ICC 20172705 ICC vs Externally Applied VCC 20172706 On-Time vs VIN and RON 20172707 Voltage at RON/SD Pin 20172708 IIN vs VIN 20172710 www.national.com 6 LM25010/LM25010Q

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FIGURE 1. Startup Sequence and provides a switch on-time which varies inversely with VIN. under-voltage lock-out, and maximum duty cycle limit. may be required (R3 in the Block Diagram).

mode, and the switching frequency varies with load current. where RL = the load resistance. close as possible to the LM25010 pins. iliary voltage be less than VIN. released to allow the soft-start capacitor (C6) to charge up. FIGURE 2. Self Biased Configuration

FIGURE 4. Inductor Current - Current Limit Operation capacitor is recommended for C4.

  • VOUT = 5V
  • VIN = 6V to 40V
  • FS = 175 kHz
  • Minimum load current = 200 mA
  • Maximum load current = 1.0A
  • Softstart time = 5 ms. R1 and R2: These resistors set the output voltage, and their ratio is calculated from: R1/R2 = (VOUT/2.5V) - 1 (10) R1/R2 calculates to 1.0. The resistors should be chosen from standard value resistors in the range of 1.0 kΩ - 10 kΩ. A value of 1.0 kΩ will be used for R1 and for R2. RON, FS: RON can be chosen using Equation 7 to set the nom- inal frequency, or from Equation 6 if the on-time at a particular VIN is important. A higher frequency generally means a small- er inductor and capacitors (value, size and cost), but higher switching losses. A lower frequency means a higher efficien- cy, but with larger components. Generally, if PC board space is tight, a higher frequency is better. The resulting on-time and frequency have a ±25% tolerance. Using equation 7 at a nominal VIN of 8V, A value of 200 k Ω will be used for R ON, yielding a nominal frequency of 161 kHz at VIN = 6V, and 203 kHz at VIN = 40V. L1: The guideline for choosing the inductor value in this ex- ample is that it must keep the circuit’s operation in continuous conduction mode at minimum load current. This is not a strict requirement since the LM25010 regulates correctly when in discontinuous conduction mode, although at a lower frequen- cy. However, to provide an initial value for L1 the above guideline will be used. 11 www.national.com LM25010/LM25010Q

FIGURE 5. Inductor Current ripple current are reached simultaneously (I PK in Figure 4). this exercise, the inductor’s tolerance is ±20%. where ILIM is the maximum guaranteed current limit threshold. in order to maintain VCC above its UVLO. capacitor with a low ESR should be used for C1. value, and maximum frequency, is determined. essary to determine the optimum value for C2.

For a 5 ms softstart time, C6 calculates to 0.022 µF. where IO is the load current, and D is the duty cycle. FIGURE 6. Example Circuit

FIGURE 11. Low Output Ripple Using Ripple Injection significantly attenuate the signal provided to FB through CB. the next section for guidelines on this issue. board’s ground plane can help considerably to dissipate heat. convection) can help reduce the junction temperature.

Physical Dimensions inches (millimeters) unless otherwise noted 14-Lead TSSOP Package 10-Lead LLP Package www.national.com 16 LM25010/LM25010Q

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