My Inquiry
My Account
Analog Devices Inc. LT1777IS#PBF
- Part No.:
- LT1777IS#PBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 16-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
LT1777IS#PBF.pdf
- Description:
- IC REG BUCK ADJ 550MA 16SO
- Quantity:
- Payment:
- Shipping:
Inventory:2,250
Please send an inquiry. Send us your inquiry, and we will respond immediately.
Product details
Overview
LT1777IS#PBF from Analog Devices (formerly Linear Technology) is a low-noise, current-mode buck switching regulator IC designed for noise-sensitive power conversion. It features programmable dI/dt limiting via external sense inductor, internally controlled dV/dt slew rates, 48V max input voltage, 700mA peak switch rating, and fixed 100kHz switching frequency with synchronization capability up to 250kHz. It is used in automotive GPS receivers, telecom power supplies, and industrial instrumentation where EMI reduction is critical.
For engineers reviewing the LT1777IS#PBF datasheet, LT1777IS#PBF pinout, LT1777IS#PBF application, or LT1777IS#PBF equivalent, key selection criteria include its dI/dt programmability, integrated dV/dt control, SO-16 thermal performance, true current-mode architecture for line rejection, and shutdown current of 30µA - all validated for operation from –40°C to 125°C.
Technical Context
The LT1777IS#PBF implements true current-mode control with internal oscillator, feedback amplifier (1.24V reference), and dual slew-rate limiting: ±dI/dt is user-programmed via external sense inductor connected between VSW and VD pins, while –dV/dt is internally generated during turn-off using a Darlington-based limiter. The control circuitry is powered from VCC (not VIN), minimizing input supply loading.
It operates with a fixed 100kHz switching frequency (±10kHz over temperature), supports external synchronization from 130kHz to 250kHz, and integrates undervoltage lockout (6.7V min VIN) with adjustable SHDN threshold (0.5V nominal). Its fused-lead SO-16 package provides low θJA = 50°C/W and connects four corner GND pins directly to the die paddle for thermal sinking.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 6.7V to 48V - supports wide-input industrial and automotive rails without pre-regulation |
| Switch Current Limit | 0.55A to 1.0A (typ 0.7A) - DC-trimmed and production-tested; higher in practice due to dI/dt programming |
| Reference Voltage | 1.240V ±15mV - precise internal bandgap reference for stable output regulation |
| Shutdown Supply Current | 30µA (typ) - enables ultra-low-power standby in battery-backed systems |
| Switching Frequency | 90–110kHz (fixed), synchronizable to 130–250kHz - allows EMI spread-spectrum alignment and noise avoidance |
| Thermal Resistance | θJA = 50°C/W - achieved via fused-corner GND pins tied to die paddle; enables high-power density layout |
| dI/dt Sense Voltage | 1.3V (typ), 0.6–2.0V (min/max) - sets current ramp limit via external inductor per V = L·di/dt |
Pinout & Package
The LT1777IS#PBF is housed in a 16-pin plastic SO (SO-16) package with fused corner GND pins (1, 8, 9, 16) electrically and thermally connected to the die paddle for enhanced heat dissipation. Pins 2, 11, and 15 are unconnected (NC).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| GND (1, 8, 9, 16) | Signal and thermal ground | Electrically tied to die substrate; must be connected to local ground plane for reference stability and thermal conduction |
| SHDN (3) | Shutdown control input | Pull below 0.5V to enter 30µA shutdown; 0.2–0.8V range enables user-defined UVLO extension |
| VCC (4) | Internal bias supply input | Powered from output rail to reduce VIN loading; requires local 0.1µF bypass if >1 inch from output capacitor |
| VD (5) | dI/dt sense reference | Connected to cathode of freewheeling diode; forms sensing node with VSW to trigger ±dI/dt limiting |
| VSW (6) | Switch emitter node | High-current switching node; traces must be short to minimize EMI and voltage spikes |
| SGND (7) | Signal ground reference | Reference for FB amplifier and internal bias; isolated from power ground currents to prevent noise coupling |
| SYNC (12) | External clock input | Logic-compatible sync input (10–90% duty); disabled automatically if FB voltage drops below 2/3 normal |
| FB (13) | Feedback amplifier inverting input | Compares output voltage against 1.24V reference; low-voltage condition slows oscillator for short-circuit protection |
| VC (14) | Control voltage output | Output of error amplifier and input to current comparator; compensation network (R+C to GND) sets loop stability |
| VIN (10) | Main power input | Supplies output switch and startup bias; requires high-ripple-current input capacitor rated for full load |
Key Features
| Feature | Design Value |
|---|---|
| Programmable dI/dt limiting | Enables user-tuned RFI reduction via external sense inductor (0–3.5µH typical), lowering high-frequency magnetic emissions |
| Internally limited dV/dt | Reduces electric-field RFI by controlling both turn-on (via Q2 capacitance) and turn-off (via –dV/dt limiter) voltage slew rates |
| True current-mode control | Delivers excellent line transient rejection and inherent cycle-by-cycle current limiting without slope compensation |
| Fused-lead SO-16 thermal design | Four corner GND pins bonded to die paddle achieve θJA = 50°C/W - critical for 700mA peak switch in compact layouts |
| Synchronization capability | Accepts external clock from 130–250kHz, enabling coordinated switching in multi-rail systems to avoid beat frequencies |
Applications
| Automotive GPS Receiver Power | Telecom Line Card Bias Supply |
|---|---|
Use Scenario: Powers sensitive RF front-end and baseband ICs in vehicle-mounted GPS modules operating from 12–36V battery rails. IC Role / Device Role / Timing Role: Primary 5V/400mA step-down regulator with dI/dt and dV/dt control to suppress conducted and radiated emissions near 1.575GHz L1 band. Use Value: Enables compliance with CISPR 25 Class 5 radiated emissions limits without added shielding or ferrites. | Use Scenario: Generates stable 3.3V or 5V bias for DSPs, PHYs, and transceivers on telecom line cards with shared 48V backplane input. IC Role / Device Role / Timing Role: High-input-voltage buck controller delivering low-noise DC power adjacent to high-speed serial interfaces (e.g., SFP+, XAUI). Use Value: Prevents switching noise coupling into data lanes by reducing dI/dt-induced magnetic field interference and dV/dt-induced capacitive coupling. |
| Industrial Sensor Signal Conditioning | Medical Diagnostic Instrumentation |
Use Scenario: Supplies precision analog front-ends (ADC drivers, instrumentation amps) in portable gas analyzers or vibration monitors. IC Role / Device Role / Timing Role: Low-EMI 3.3V/200mA regulator placed near noise-sensitive signal chains; uses 1µH sense inductor to target <1.4A/µs dI/dt. Use Value: Maintains >90dB SNR in 24-bit delta-sigma ADCs by eliminating switching artifacts in baseband measurement bandwidth. | Use Scenario: Powers isolated analog acquisition stages in ultrasound beamformers or EEG amplifiers requiring ultra-clean 5V/300mA rails. IC Role / Device Role / Timing Role: Secondary regulated supply downstream of isolation barrier; leverages LT1777IS#PBF's 30µA shutdown for sleep-mode power gating. Use Value: Meets IEC 60601-1 leakage current and EMC immunity requirements without compromising system responsiveness. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar buck regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC3631EMSE#PBF | Higher efficiency (95% typ), 36V max input, no dI/dt programming; uses constant-on-time control instead of current mode | Lacks programmable slew-rate control - unsuitable where spectral EMI shaping is required | Select when peak efficiency >88% and EMI filtering is handled externally |
| TPS54340DDAR | 42V max input, 3.5A switch, no dV/dt control; includes soft-start and power-good, but no dI/dt sense pin | Higher current capability but generates broader-spectrum RFI - requires additional LC filtering | Select for cost-sensitive, non-RFI-critical 3A applications with standard buck layout |
Compared with LTC3631EMSE#PBF and TPS54340DDAR, the LT1777IS#PBF uniquely delivers deterministic dI/dt and dV/dt control for EMI-limited environments, trades off some efficiency for spectral shaping, and maintains robust current-mode stability across wide input ranges - making it irreplaceable in certified automotive and medical power designs.
Availability
LT1777IS#PBF is available at Aetrix Electronics and suitable for automotive GPS receivers, telecom line card bias supplies, and industrial sensor signal conditioning requiring stable component supply across extended temperature ranges and long production lifecycles.
Supply support for LT1777IS#PBF 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
Analog Devices, Inc. (ADI) is a global leader in high-performance analog, mixed-signal, and digital signal processing technologies, serving industrial, automotive, communications, and healthcare markets.
The LT1777IS#PBF belongs to ADI's legacy Linear Technology power management portfolio, specifically engineered for low-EMI DC/DC conversion in noise-critical applications where spectral content-not just average ripple-must be controlled.
FAQ
What is the maximum input voltage rating for the LT1777IS#PBF?
The LT1777IS#PBF has an absolute maximum input voltage rating of 48V on the VIN pin. Operation above this voltage risks permanent damage. The device is specified to operate continuously from 6.7V to 48V, with guaranteed performance over the full –40°C to 125°C junction temperature range. This makes the LT1777IS#PBF suitable for 24V and 36V industrial and automotive systems where transient overvoltage events must be accommodated within safe margins.
How does the dI/dt limiting function work in the LT1777IS#PBF?
The LT1777IS#PBF implements dI/dt limiting by sensing voltage across an external sense inductor placed between the VSW pin and the cathode of the freewheeling diode. When the voltage across that inductor reaches ±2×VBE (~1.3V typ), internal circuitry adjusts base drive to the output switch to clamp the current slew rate. The actual dI/dt is inversely proportional to the sense inductor value, allowing users to tune EMI behavior. This function is fully documented in the LT1777IS#PBF Applications Information section and verified in oscilloscope waveforms (Figures 2a/b).
Can the LT1777IS#PBF be synchronized to an external clock, and what is the valid frequency range?
Yes, the LT1777IS#PBF can be synchronized to an external clock applied to the SYNC pin. It accepts logic-level signals (10–90% duty cycle) from 130kHz to 250kHz, as confirmed in the Electrical Characteristics table (synchronization range: 130–250kHz, min sync amplitude: 1.5V). The internal oscillator is disabled when SYNC is active. If unused, the SYNC pin must be grounded. This feature enables coordinated switching in multi-rail systems to avoid heterodyne beat frequencies - a key capability of the LT1777IS#PBF not found in many standard buck regulators.
What is the purpose of the VD pin on the LT1777IS#PBF?
On the LT1777IS#PBF, the VD pin serves as the reference node for the ±dI/dt limiting circuit. It is connected to the cathode of the freewheeling diode and forms one side of the differential sense path with the VSW pin. The voltage difference between VSW and VD determines when the dI/dt limiter activates. This architecture allows the LT1777IS#PBF to detect rapid current changes in both switch turn-on and turn-off phases, enabling bidirectional slew-rate control essential for broadband EMI suppression.
Does the LT1777IS#PBF require external compensation, and where is it applied?
Yes, the LT1777IS#PBF requires external frequency compensation applied to the VC pin (Pin 14), which is the output of the internal error amplifier and input to the current comparator. Compensation is implemented via a capacitor (or RC network) connected between VC and SGND. The value and configuration determine loop stability, transient response, and phase margin. The LT1777IS#PBF datasheet provides design equations and example networks for common output configurations - omitting this compensation will result in oscillation or poor load regulation.
LT1777IS#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 16-SOIC (0.154", 3.90mm Width)
- Packaging:
- Tube
- Product Status:
- Active
- Function:
- Step-Down
- Output Configuration:
- Positive
- Topology:
- Buck
- Output Type:
- Adjustable
- Number of Outputs:
- 1
- Voltage - Input (Min):
- 7.4V
- Voltage - Input (Max):
- 48V
- Voltage - Output (Min/Fixed):
- 1.24V
- Voltage - Output (Max):
- 30V
- Current - Output:
- 550mA (Switch)
- Frequency - Switching:
- 100kHz
- Synchronous Rectifier:
- No
- Operating Temperature:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 16-SO
LT1777IS#PBF FAQ
1.How can I place an order for LT1777IS#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT1777IS#PBF 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 LT1777IS#PBF reliable?
The price and inventory of LT1777IS#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT1777IS#PBF is usually 5 days.
3.What payment methods are accepted for LT1777IS#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT1777IS#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT1777IS#PBF?
LT1777IS#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT1777IS#PBF 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 LT1777IS#PBF?
For technical support, including LT1777IS#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT1777IS#PBF requirements.
6.How does Aetrix verify that LT1777IS#PBF is sourced from the original manufacturer or authorized distributors?
All LT1777IS#PBF 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 LT1777IS#PBF meets industry standards.
7.What is the process for return or replacement of LT1777IS#PBF?
All LT1777IS#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LT1777IS#PBF, 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 LT1777IS#PBF part is unused and in its original packaging.
Return procedure for LT1777IS#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
LT1777IS#PBF Tags
-
TPS562201DDCR
Texas Instruments
-
MC34063ABD-TR
STMicroelectronics
-
TPS561201DDCR
Texas Instruments
-
MC33063ADR
Texas Instruments
-
MC34063ADR
Texas Instruments
-
TPS560200DBVR
Texas Instruments
-
AP3012KTR-G1
Diodes Incorporated
-
TLV61048DBVR
Texas Instruments
-
AZ34063UMTR-G1
Diodes Incorporated
-
TPS562200DDCR
Texas Instruments
-
AP62300TWU-7
Diodes Incorporated
-
MC34063EBD-TR
STMicroelectronics
Tech Hub
A practical engineering guide to 3.3V and 5V logic compatibility, input thresholds, resistor dividers, translator ICs, MOSFET level shifting, I2C pull-ups, timing limits and power-sequencing risks.
The 74HC595 uses push-pull logic outputs, while the TPIC6B595 uses 50 V open-drain DMOS sinks for higher-power loads. This guide compares timing, current limits, 3.3 V interfacing, load wiring, thermal…
The 74HC595 converts serial data into eight stable parallel outputs. This guide covers pin functions, shift and storage timing, OE and MR behavior, drive-current limits, cascading, voltage compatibilit…
A technical comparison of level-sensitive latches and edge-triggered flip-flops, covering timing windows, setup and hold limits, master–slave operation, time borrowing, race-through, HDL inference and…
A D latch stores one bit while Enable controls when data can pass. This reference covers gate-level operation, truth tables, transparency, setup and hold timing, LE versus OE, common ICs and practical …
An SR latch stores one bit through cross-coupled feedback. This engineering reference covers NOR and NAND implementations, truth tables, forbidden-state recovery, gated operation, switch debouncing, fa…
Latch circuits retain one bit through feedback. This technical reference covers SR and D latches, truth tables, transparency, timing limits, latch-versus-flip-flop behavior, applications and common log…
An engineering guide to LED driver operation, constant-current and constant-voltage outputs, linear and switching topologies, dimming, IC selection, calculations, replacement compatibility, and fault c…
Operational amplifier guide covering op amp basics, feedback, ideal vs real op amps, common configurations, buffer circuits, offset, bias current, gain-bandwidth, slew rate, rail-to-rail limits and sel…
Jumper cables guide covering safe connection order, red and black clamp placement, final ground connection, cable gauge, length, clamp quality, copper vs CCA cables, jump starter comparison and battery…
