LM51581-Q1
Boost/SEPIC/Flyback Converter with Integrated SwitchThe LM51581-Q1 is a boost/sepic/flyback converter with integrated switch from Texas Instruments. View the full LM51581-Q1 datasheet below including key specifications, electrical characteristics, absolute maximum ratings.
LM51581-Q1 shares its datasheet with LM51581, whose page lists every part number it covers.
Official LM51581-Q1 datasheet (PDF) — the source this page was extracted from.
LM51581-Q1 Key Specifications
| Parameter | Value |
|---|---|
| Switch RDSON | 133mΩ |
| Minimum On Time | 80ns |
| Shutdown Current | ≤2.6µA |
| Maximum SW Voltage | 83V (85V abs max) |
| Input Voltage Range | -3.2V to 60V (65V abs max) |
| Switching Frequency | 100kHz to 2.2MHz |
| Overvoltage Threshold | 110% of VREF (typ) |
| Maximum Output Voltage | 83V (85V abs max) |
| Feedback Reference Voltage | 1V ±1% |
| Operating Quiescent Current | ≤670µA |
| Minimum Boost Supply Voltage | 1.5V (with BIAS >= 3.2V) |
| Error Amplifier Transconductance | 2mA/V |
| Internal MOSFET Current Limit (Typ) | 1.875A |
| Internal Switch Current Limit (Min) | 1.63A |
LM51581-Q1 Overview
Part: LM51581 (LM5158x family) — Texas Instruments
Type: Non-synchronous Boost / SEPIC / Flyback Converter with integrated switch
Description: 1.5–60 V input (with BIAS ≥ 3.2 V), up to 83 V output, 85 V / 1.63 A (min peak current limit) integrated 133 mΩ switch, with switching frequency programmable from 100 kHz to 2.2 MHz and optional dual random spread spectrum.
Operating Conditions:
- Supply voltage: 1.5–60 V boost input (BIAS pin 3.2–60 V)
- Operating junction temperature: -40 to 125 °C
- Boost output up to 83 V (SW pin ≤ 85 V during transients)
- Switching frequency: 100–2200 kHz
Absolute Maximum Ratings:
- BIAS to AGND: 65 V
- SW to AGND (DC): 85 V
- VCC to AGND: 5.8 V
- PGOOD to AGND: 18 V
- Junction temperature: 150 °C
- Storage temperature: -55 to 150 °C
Key Specs:
- Shutdown current (VBIAS = 12 V, VUVLO = 0 V): 2.6 μA typ, 5 μA max
- Operating current (VBIAS = 12 V, RT = 220 kΩ): 670 μA typ, 850 μA max
- Internal MOSFET current limit (LM51581): 1.63 / 1.875 / 2.12 A (min/typ/max)
- FB reference voltage: 0.99 / 1 / 1.01 V (min/typ/max)
- VCC regulation (VBIAS = 8 V, IVCC = 18 mA): 4.66 / 4.9 / 5.14 V
- Switching frequency (RT = 9.09 kΩ): 1980 / 2200 / 2420 kHz
- Minimum on-time (RT = 9.09 kΩ): 80 ns typ
- Soft-start current: 9 / 10 / 11 μA
- Thermal resistance RθJA: 45.6 °C/W
Features:
- Wide input range for battery applications, with input transient protection up to 65 V
- Low shutdown IQ (≤ 2.6 μA) and low operating IQ (≤ 670 μA)
- Integrated error amplifier enabling primary-side regulation (flyback) without an optocoupler
- Optional dual random spread spectrum for EMI mitigation
- Optional clock synchronization
- Programmable line UVLO
- Constant current limit over input voltage range
- Optional hiccup-mode overload protection
- OVP and thermal shutdown
- Adjustable soft start
- PGOOD indicator
- ±1% feedback reference
Applications:
- Battery-powered wide-input boost, SEPIC and flyback converters
- Multi-output flyback without optocoupler
- LED bias supplies
- Loop-powered fire detection
- Power modules
- Hold-up capacitor chargers
- Industrial PLC
- Piezo / motor driver bias supplies
- Inverter bias supplies
Package:
- WQFN-16 (RTE), 3.00 mm × 3.00 mm
LM51581-Q1 Pin Configuration
图 7-1. RTE Package 16-Pin WQFN Top View
表 7-1. Pin Functions
| PIN - NO. | PIN - NAME | TYPE (1) | DESCRIPTION |
|---|---|---|---|
| 1, 16 | PGND | P | Power ground pin. Source connection of the internal N-channel power MOSFET |
| 2 | VCC | P | Output of the internal VCC regulator and supply voltage input of the internal MOSFET driver. Connect a 1-μF ceramic bypass capacitor from this pin to PGND. |
| 3 | BIAS | P | Supply voltage input to the VCC regulator. Connect a bypass capacitor from this pin to PGND. |
| 4 | PGOOD | O | Power-good indicator. An open-drain output, which goes low if FB is below the undervoltage threshold (V UVTH ). Connect a pullup resistor to the system voltage rail. |
| 5 | RT | I | Switching frequency setting pin. The switching frequency is programmed by a single resistor between RT and AGND. |
| 6 | EN/UVLO/ SYNC | I | Enable pin. The converter shuts down when the pin is less than the enable threshold (V EN ). |
| 6 | EN/UVLO/ SYNC | I | Undervoltage lockout programming pin. The converter start-up and shutdown levels can be programmed by connecting this pin to the supply voltage through a voltage divider. If using a programmable UVLO, connect the low-side UVLO resistor to AGND. This pin must not be left floating. Connect to the BIAS pin if not used. |
| 6 | EN/UVLO/ SYNC | I | External synchronization clock input pin. The internal clock can be synchronized to an external clock by applying a negative pulse signal into the pin. |
| 7 | AGND | G | Analog ground pin. Connect to the analog ground plane through a wide and short path. |
| 8 | COMP | O | Output of the internal transconductance error amplifier. Connect the loop compensation components between this pin and AGND. |
| 9 | FB | I | Inverting input of the error amplifier. Connect a voltage divider to set the output voltage in boost, SEPIC, or primary-side regulated flyback topologies. Connect the low-side feedback resistor as close to AGND as possible. |
| 10 | SS | I | Soft-start time programming pin. An external capacitor and an internal current source set the ramp rate of the internal error amplifier reference during soft start. Connect the ground connection of the capacitor to AGND. |
| 11 | MODE | I | MODE = 0 V or connect to AGND during initial power up: Hiccup mode protection is disabled and spread spectrum is disabled. |
| 11 | MODE | I | MODE = 370 mV or connect a 37.4-kΩ resistor between this pin and AGND during initial power up: Hiccup mode protection is enabled and spread spectrum is enabled. |
| 11 | MODE | I | MODE = 620 mV or connect a 62.0-kΩ resistor between this pin and AGND during initial power up: Hiccup mode protection is enabled and spread spectrum is disabled. |
| 11 | MODE | I | MODE > 1 V or connect a 100-kΩ resistor between this pin and AGND during initial power up: Hiccup mode protection is disabled and spread spectrum is enabled. |
表 7-1. Pin Functions
| PIN - NO. | PIN - NAME | TYPE (1) | DESCRIPTION |
|---|---|---|---|
| 13, 14 | SW | Switch pin. Drain connection of the internal N-channel power MOSFET | |
| 12, 15 | NC | - | No internal electrical contact |
| - | EP | - | Exposed pad of the package. The exposed pad must be connected to AGND and the large ground copper plane to decrease thermal resistance. |
LM51581-Q1 Electrical Characteristics
Typical values correspond to TJ = 25°C. Minimum and maximum limits apply over TJ = -40°C to 125°C. Unless otherwise stated, V BIAS = 12 V, RT = 9.09 kΩ
| PARAMETER | PARAMETER | TEST CONDITIONS | MIN | TYP | MAX | UNIT |
|---|---|---|---|---|---|---|
| SUPPLY CURRENT | SUPPLY CURRENT | SUPPLY CURRENT | SUPPLY CURRENT | SUPPLY CURRENT | SUPPLY CURRENT | SUPPLY CURRENT |
| I SHUTDOWN(BIAS) | BIAS shutdown current | V BIAS = 12 V, V UVLO = 0 V | 2.6 | 5 | μA | |
| I OPERATING(BIAS) | BIAS operating current | V BIAS = 12 V, V UVLO = 2.0 V, V FB = V REF , R T = 220 kΩ | 670 | 850 | μA | |
| VCC REGULATOR | VCC REGULATOR | VCC REGULATOR | VCC REGULATOR | VCC REGULATOR | VCC REGULATOR | VCC REGULATOR |
| V VCC-REG | VCC regulation | V BIAS = 8 V, I VCC = 18 mA | 4.66 | 4.9 | 5.14 | V |
| V VCC- UVLO(RISING) | VCC UVLO threshold | VCC rising | 3.05 | 3.10 | 3.15 | V |
| VCC UVLO hysteresis | VCC falling | 0.1 | V | |||
| ENABLE | ENABLE | ENABLE | ENABLE | ENABLE | ENABLE | ENABLE |
| V EN(RISING) | Enable threshold | EN rising | 0.4 | 0.52 | 0.7 | V |
| V EN(FALLING) | Enable threshold | EN falling | 0.33 | 0.49 | 0.63 | V |
| V EN(HYS) | Enable hysteresis | EN falling | 0.03 | V | ||
| UVLO/SYNC | UVLO/SYNC | UVLO/SYNC | UVLO/SYNC | UVLO/SYNC | UVLO/SYNC | UVLO/SYNC |
| V UVLO(RISING) | UVLO / SYNC threshold | UVLO rising | 1.425 | 1.5 | 1.575 | V |
| V UVLO(FALLING) | UVLO / SYNC threshold | UVLO falling | 1.370 | 1.45 | 1.520 | V |
| V UVLO(HYS) | UVLO / SYNC threshold hysteresis | UVLO falling | 0.05 | V | ||
| I UVLO | UVLO hysteresis current | V UVLO = 1.6 V | 4 | 5 | 6 | μA |
| MODE, SPREAD SPECTRUM | MODE, SPREAD SPECTRUM F SW modulation (upper limit) F SW modulation (lower limit) | MODE, SPREAD SPECTRUM | MODE, SPREAD SPECTRUM 7.8% -7.8% | MODE, SPREAD SPECTRUM | MODE, SPREAD SPECTRUM | MODE, SPREAD SPECTRUM |
| SOFT START | SOFT START | SOFT START | SOFT START | SOFT START | SOFT START | SOFT START |
| I SS | Soft-start current SS pulldown switch R DSON | 9 | 10 50 | 11 | μA Ω | |
| PULSE WIDTH MODULATION | PULSE WIDTH MODULATION | PULSE WIDTH MODULATION | PULSE WIDTH MODULATION | PULSE WIDTH MODULATION | PULSE WIDTH MODULATION | PULSE WIDTH MODULATION |
| fsw1 | Switching frequency | R T = 220 kΩ | 85 | 100 | 115 | kHz |
LM51581-Q1 Absolute Maximum Ratings
Over the recommended operating junction temperature range (1)
| MIN | MAX | UNIT | ||
|---|---|---|---|---|
| Input | BIAS to AGND | -0.3 | 65 | V |
| Input | UVLO to AGND | -0.3 | V BIAS + 0.3 | V |
| Input | SS, RT to AGND (2) | -0.3 | 3.8 | V |
| Input | FB to AGND | -0.3 | 4.0 | V |
| Input | MODE to AGND | -0.3 | 3.8 | V |
| Input | PGND to AGND | -0.3 | 0.3 | V |
| VCC to AGND | -0.3 | 5.8 (3) | V | |
| PGOOD to AGND (4) | -0.3 | 18 | V | |
| COMP to AGND (5) | -0.3 | V | ||
| SW to AGND (DC) | -0.3 | 85 | V | |
| SW to AGND (5-ns transient) | -6 | V | ||
| Junction temperature, T J (6) | Junction temperature, T J (6) | -40 | 150 | °C |
| Storage temperature, T stg | Storage temperature, T stg | -55 | 150 | °C |
- (1) Operation outside the Absolute Maximum Ratings may cause permanent device damage. Absolute Maximum Ratings do not imply functional operation of the device at these or any other conditions beyond those listed under Recommended Operating Conditions . If used outside the Recommended Operating Conditions but within the Absolute Maximum Ratings , the device may not be fully functional, and this may affect device reliability, functionality, performance, and shorten the device lifetime.
- (2) These pins are not specified to have an external voltage applied.
- (3) Operating lifetime is de-rated when the pin voltage is greater than 5.5 V.
- (4) The maximum current sink is limited to 1 mA when VPGOOD > VBIAS.
- (5) This pin has an internal max voltage clamp which can handle up to 1.6 mA.
- (6) High junction temperatures degrade operating lifetimes. Operating lifetime is de-rated for junction temperatures greater than 125°C.
LM51581-Q1 Recommended Operating Conditions
Over the recommended operating junction temperature range (1)
| MIN | NOM | MAX | UNIT | ||
|---|---|---|---|---|---|
| V SUPPLY | Boost converter input (when BIAS ≥ 3.2 V) | 1.5 | 60 | V | |
| V LOAD | Boost converter output | V SUPPLY | 83 (2) | V | |
| V BIAS | BIAS input (3) | 3.2 | 60 | V | |
| V UVLO | UVLO input | 0 | 60 | V | |
| V FB | FB input | 0 | 4.0 | V | |
| I SW | Switch current | 0 | See note (4) | A | |
| f SW | Typical switching frequency | 100 | 2200 | kHz | |
| f SYNC | Synchronization pulse frequency | 100 | 2200 | kHz | |
| T J | Operating junction temperature | -40 | 125 | °C |
-
(2) The boost converter output can be up to 83 V, but the SW pin voltage should be less than or equal to 85 V during transient.
-
(3) The BIAS pin operating range is from 3.2 V to 60 V when VCC is supplied from the internal VCC regulator.
-
(4) The maximum switch current is limited by pre-programmed peak current limit (ILIM) when TJ < TTSD.
LM51581-Q1 Thermal Information
| THERMAL METRIC (1) | LM5158x RTE(QFN) - 16 PINS | UNIT | |
|---|---|---|---|
| R θJA | Junction-to-ambient thermal resistance (LM5158EVM-BST) | 32.7 | °C/W |
| R θJA | Junction-to-ambient thermal resistance | 45.6 | °C/W |
| R θJC(top) | Junction-to-case (top) thermal resistance | 44.8 | °C/W |
| R θJB | Junction-to-board thermal resistance | 19.1 | °C/W |
| Ψ JT | Junction-to-top characterization parameter (LM5158EVM-BST) | 0.6 | °C/W |
| Ψ JT | Junction-to-top characterization parameter | 0.8 | °C/W |
| Ψ JB | Junction-to-board characterization parameter (LM5158EVM-BST) | 15.1 | °C/W |
| Ψ JB | Junction-to-board characterization parameter | 19.1 | °C/W |
| R θJC(bot) | Junction-to-case (bottom) thermal resistance | 6.7 | °C/W |
LM51581-Q1 Typical Application
TI provides application notes explaining how to design boost and flyback converters using the device. These comprehensive application notes include component selections and loop response optimization.
See these application reports for more information on loop response and component selection:
Variants on the same datasheet
These parts have exact links to the same datasheet. They are candidates to compare, not verified drop-in replacements; check package, pinout and electrical limits.
| Part Number | Manufacturer | Package |
|---|---|---|
| LM51581 | Texas Instruments | WQFN-16 3x3mm |
| LM51581RTER | Texas Instruments | WQFN-16 3x3mm |
| LM51581RTER.A | Texas Instruments | WQFN-16 |
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