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Home > Products > Integrated Circuits (ICs) > Power Management (PMIC) > DC DC Switching Controllers

STMicroelectronics L5991AD13TR

Name: L5991AD13TR
Brand: STMicroelectronics
SKU: L5991AD13TR
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: L5991AD13TR

Manufacturer:: STMicroelectronics

Category:: DC DC Switching Controllers

Package:: 16-SOIC (0.154", 3.90mm Width)

Datasheet:: L5991AD13TR.pdf

Description:: IC REG CTRLR FLYBACK 16SOIC

Quantity:: RFQ Add To RFQ list

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Product details

Overview

L5991AD13TR from STMicroelectronics is a primary-side current-mode PWM controller IC for offline and DC-DC flyback power supplies, featuring programmable soft start (14–26 µA charge current), 100 ns leading-edge blanking on current sense, 1 A peak totem-pole output drive, and standby mode with oscillator frequency reduction under light load. It operates up to 1 MHz, supports IN/OUT synchronization, and integrates precise 5.0 V ±1.5% reference, UVLO with 0.5 V hysteresis, and latched disable for overvoltage protection.

For engineers reviewing the L5991AD13TR datasheet, L5991AD13TR pinout, L5991AD13TR application, or L5991AD13TR equivalent, key selection considerations include its dual-frequency standby operation (f_osc/f_SB ≤ 5.5), programmable duty cycle (0–93% via pin 3 voltage), internal 100 ns blanking for noise-immune current sensing, and SO16 package compatibility with DIP16 footprint.

Technical Context

The L5991AD13TR implements fixed-frequency current-mode control using a BCD60II process, with oscillator timing set by external R_A, R_B, and C_T components. Its standby function monitors V_COMP to detect light-load conditions: when V_COMP falls below VT1 = 2.5 V (falling), oscillator frequency drops to f_SB; recovery occurs at VT2 = 4.0 V (rising), with hysteresis preventing oscillation near threshold.

Current sensing uses internal 100 ns blanking and a 1.2 V fault threshold (1.1–1.3 V) with hiccup-mode restart on overcurrent. The error amplifier delivers 60–90 dB open-loop gain, 1.7–4 MHz unity-gain bandwidth, and 8 V/µs slew rate, with compensation network connected between pins 5 (VFB) and 6 (COMP).

Key Specifications

Parameter	Value and Actual Design Meaning
Supply Voltage (VCC)	7.8–16 V startup; 7–11 V operating range with 0.5–0.8 V hysteresis - ensures reliable turn-on/off in wide-input AC-DC designs.
Reference Voltage	5.0 V ±1.5% at 25°C, 4.80–5.13 V total variation - provides stable bias for feedback and timing circuits.
Switching Frequency	Up to 1 MHz (typ. 100 kHz at V_REF on pin 15); programmable via R_A/R_B/C_T - enables high-density transformer design with low EMI.
Output Drive	1 A peak source/sink capability - directly drives power MOSFET gates without external buffer in most 65–100 W applications.
Soft Start Current	14–26 µA (ISSC) - sets controlled ramp time for V_COMP to prevent inrush and ensure monotonic startup.
Current Sense Threshold	1.2 V (typ.), 1.1–1.3 V range - defines pulse-by-pulse current limit point for primary-side overcurrent protection.
Standby Thresholds	VT1 = 2.5 V (falling), VT2 = 4.0 V (rising) - enables automatic frequency scaling to reduce light-load switching losses in flyback converters.

Pinout & Package

Package: SO16 (Small Outline, 16-pin, 150 mil width), RoHS-compliant, surface-mount compatible with DIP16 footprint.

Pin/Terminal	Circuit Role	Design Meaning
1 SYNC	In/Out synchronization interface	Master: outputs 4 V, 7 mA pulses on oscillator falling edge; Slave: edge-triggered sync input - enables multi-controller phase alignment or external clock locking.
2 RCT	Oscillator timing node	Charges C_T via R_A//R_B (normal) or R_A only (standby) - sets f_osc and f_SB independently per Equation (1)/(2).
3 DC	Duty cycle control input	Voltage 1–3 V sets max duty cycle 0–93%; <1 V disables output - enables dynamic duty limiting or analog shutdown.
4 VREF	5.0 V reference output	±1.5% accuracy, 1–10 mA load capability - powers external circuitry and sets timing component values.
5 VFB	Error amp inverting input	Compares feedback signal to internal 2.5 V reference - forms core of voltage regulation loop.
6 COMP	Error amp output	Drives PWM comparator; monitored for standby activation - requires RC compensation network to pin 5 for loop stability.
7 SS	Soft-start capacitor node	Charged at 14–26 µA to ~7 V - clamps COMP during startup to limit inrush and enable controlled ramp-up.
8 VCC	Signal circuit supply	UVLO threshold 7.8–9 V (L5991A); internal 25 V Zener - powers control logic; low 40–120 µA start-up current reduces no-load loss.
9 VC	Power stage supply	Separate supply for gate driver - decoupled with local capacitor to PGND to sustain pulsed 1 A gate currents without noise coupling.
10 OUT	High-current gate driver output	1 A peak totem-pole output - directly drives N-channel MOSFET gates; rise/fall times 50–100 ns / 20–60 ns (C_O = 1–2.5 nF).
11 PGND	Power ground return	Low-impedance return path for gate drive and power switch current - must be physically separated from SGND to avoid noise injection.
12 SGND	Signal ground reference	Reference for VREF, VFB, COMP, SS - connects to system signal ground; kept separate from PGND to maintain error amp accuracy.
13 ISEN	Current sense input	Accepts voltage from primary-side sense resistor; 100 ns internal blanking suppresses switching noise - enables accurate peak current detection.
14 DIS	Latched disable input	Logic-high (>2.4 V) disables PWM and forces OUT low - used for overvoltage protection or system-level shutdown; must not float.
15 DC-LIM	Duty cycle clamp control	Connected to VREF → limits max duty to 50%; floating → no limit - adds safety margin against transformer saturation.
16 ST-BY	Standby mode control	Resistor to RCT sets standby entry point; tied to VREF or floating if unused - enables automatic light-load efficiency optimization in flyback topologies.

Key Features

Feature	Design Value
Programmable soft start	14–26 µA internal current source charges external capacitor - eliminates output overshoot and inrush stress during cold start.
100 ns leading-edge blanking	Internally masks current sense signal at switch turn-on - prevents false overcurrent trips from transformer leakage spikes.
Standby frequency scaling	Automatically reduces oscillator frequency under light load via V_COMP monitoring - cuts switching losses while preserving fast transient response at full load.
IN/OUT synchronization	Configurable master/slave operation on pin 1 - enables interleaved multi-phase designs or lock to system clock for EMI reduction.
Fully latched PWM logic	Double-pulse suppression and hiccup-mode restart on overcurrent - ensures safe shutdown and automatic recovery without manual reset.

Applications

AC-DC Adapter

Industrial SMPS

Use Scenario: 12 V/2 A universal-input offline adapter for consumer electronics.

IC Role / Device Role / Timing Role: Primary-side PWM controller regulating output via optocoupler feedback; sets 65 kHz switching frequency and 45% max duty cycle.

Use Value: 100 ns blanking rejects transformer ringing, enabling stable regulation with minimal snubber loss.

Use Scenario: 24 V/5 A industrial power supply with wide input range (85–264 VAC) and tight hold-up time.

IC Role / Device Role / Timing Role: Primary controller implementing valley-switching flyback with standby mode activated below 10% load.

Use Value: Standby frequency reduction from 100 kHz to 20 kHz cuts no-load power consumption by >35% vs fixed-frequency operation.

LED Driver

USB PD Power Block

Use Scenario: Constant-current LED driver for architectural lighting (36 V/0.7 A output).

IC Role / Device Role / Timing Role: Primary-side controller with secondary-side current feedback; uses pin 3 voltage to clamp duty cycle at 60% for thermal derating.

Use Value: Programmable duty cycle prevents transformer saturation during dimming transients and overtemperature events.

Use Scenario: Dual-port 65 W USB PD power block with adaptive voltage regulation (5–20 V).

IC Role / Device Role / Timing Role: Primary controller supporting IN/OUT sync to coordinate with secondary-side MCU for dynamic voltage scaling.

Use Value: Pin 1 synchronization ensures clean spectral spreading across multiple converters, easing EMI filter design.

Equivalent & Alternatives

The following parts are listed as comparable options for similar primary-side PWM controller applications.

Alternative Part	Technical Difference	Application Difference	Selection Advice
UC3844BD1R2G	Fixed 52 kHz frequency; no standby mode; 1 A output; no sync pin; 1 V current sense threshold	Lacks light-load efficiency optimization and external synchronization - suitable only for cost-sensitive, fixed-frequency designs	Select when board space is constrained and variable frequency is unnecessary; verify 1 V threshold compatibility with sense resistor sizing.
ICE2A265	Integrated 650 V MOSFET; 65 kHz fixed frequency; no soft start programming; 0.5 A output drive	Monolithic solution eliminates external FET but sacrifices layout flexibility and thermal separation - limited to <35 W	Choose for ultra-compact, low-component-count adapters where integrated FET voltage rating suffices and soft start tuning is not required.

Compared with UC3844BD1R2G and ICE2A265, the L5991AD13TR uniquely combines programmable frequency scaling, 100 ns blanking, and 1 A gate drive in SO16 - making it optimal for mid-power (35–100 W) flyback designs requiring high light-load efficiency, robust noise immunity, and flexible layout.

Availability

L5991AD13TR is available at Aetrix Electronics and suitable for AC-DC adapters, industrial SMPS, LED drivers, and USB PD power blocks requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.

Supply support for L5991AD13TR includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

STMicroelectronics is a global semiconductor leader headquartered in Geneva, Switzerland, designing and manufacturing analog, microcontroller, power, and sensor solutions for automotive, industrial, and consumer markets.

The L5991AD13TR belongs to ST's MultiPower BCD technology family, engineered specifically for high-voltage, high-efficiency offline power conversion - emphasizing robustness, precision timing, and integrated protection for flyback and forward converter topologies.

FAQ

What is the minimum recommended value for the soft-start capacitor (Css) on pin 7?

The soft-start capacitor (Css) should be selected to achieve a desired ramp time T_ss ≈ 3 × R_sense × I_Qpk / (I_SSC × C_ss). For typical 10–50 ms startup, Css ranges from 100 nF to 1 µF. A 470 nF X7R ceramic capacitor is commonly used with 22 Ω sense resistor and 1 A peak current, yielding ~25 ms ramp. Larger values increase startup time but improve inrush control.

How does the ST-BY pin (pin 16) interact with the RCT network to set standby frequency?

Pin 16 (ST-BY) connects to RCT via an external resistor to define the threshold at which standby activates. When V_COMP falls below 2.5 V, ST-BY pulls low, disconnecting R_B from the RCT node - leaving only R_A to charge C_T. This increases the oscillator period, reducing frequency from f_osc = 1/(C_T × 0.693 × (R_A//R_B) + K_T) to f_SB = 1/(C_T × 0.693 × R_A + K_T), where K_T = 90 ns or 160 ns depending on pin 15 connection.

Can the L5991AD13TR drive a 600 V MOSFET directly without a gate driver IC?

Yes - the L5991AD13TR's 1 A peak output drive (pin 10) can directly drive standard 600 V N-channel MOSFETs with gate charge Q_g ≤ 30 nC at 65–100 kHz. For example, STP16NF06L (Q_g = 22 nC) achieves <100 ns turn-on with 10 Ω series gate resistor. Layout must minimize loop inductance, and VC (pin 9) must be decoupled with ≥10 µF low-ESR capacitor to PGND.

What happens if the DIS pin (pin 14) is left unconnected?

The DIS pin must never be left floating: internal bias may cause unpredictable latch behavior or partial disable. If unused, tie pin 14 directly to SGND (pin 12). Leaving it open risks intermittent shutdown due to noise coupling, especially in high-dV/dt environments. The 1 µA input bias current and 2.4–2.6 V shutdown threshold require solid logic-low (<0.8 V) or logic-high (>3.0 V) assertion for reliable operation.

L5991AD13TR Specifications

Product attributes: Attribute value

Manufacturer:: STMicroelectronics

Series:: -

Package/Case:: 16-SOIC (0.154", 3.90mm Width)

Packaging:: Tape & Reel (TR)

Product Status:: Active

Output Type:: Transistor Driver

Function:: Step-Up/Step-Down

Output Configuration:: Positive, Isolation Capable

Topology:: Flyback

Number of Outputs:: 1

Output Phases:: 1

Voltage - Supply (Vcc/Vdd):: 7.6V ~ 20V

Frequency - Switching:: Up to 1MHz

Duty Cycle (Max):: 93%

Synchronous Rectifier:: Yes

Clock Sync:: No

Serial Interfaces:: -

Control Features:: Current Limit, Frequency Control, Soft Start

Operating Temperature:: -40°C ~ 150°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Surface Mount

Supplier Device Package:: 16-SO

L5991AD13TR FAQ

1.How can I place an order for L5991AD13TR through Aetrix?

Please submit a Request for Quotation (RFQ) for L5991AD13TR on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.

2.Are the price and stock information for L5991AD13TR reliable?

The price and inventory of L5991AD13TR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for L5991AD13TR is usually 5 days.

3.What payment methods are accepted for L5991AD13TR?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for L5991AD13TR transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for L5991AD13TR?

L5991AD13TR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your L5991AD13TR order is processed, you will receive an email with the shipment details and tracking number.

Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.

5.How can I obtain technical support or documentation for L5991AD13TR?

For technical support, including L5991AD13TR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your L5991AD13TR requirements.

6.How does Aetrix verify that L5991AD13TR is sourced from the original manufacturer or authorized distributors?

All L5991AD13TR products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that L5991AD13TR meets industry standards.

7.What is the process for return or replacement of L5991AD13TR?

All L5991AD13TR units undergo pre-shipment inspection (PSI). If there is an issue with L5991AD13TR, returns or replacements are accepted under the following conditions:

1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.

2.The issue is reported within 90 days of delivery.

3.The L5991AD13TR part is unused and in its original packaging.

Return procedure for L5991AD13TR:

1.Submit a request within 90 days.

2.Obtain a Return Material Authorization (RMA) from Aetrix.

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