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Analog Devices Inc. LTC1553CSW#PBF
- Part No.:
- LTC1553CSW#PBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- Special Purpose Regulators
- Package:
- 20-SOIC (0.295", 7.50mm Width)
- Datasheet:
-
LTC1553CSW#PBF.pdf
- Description:
- IC REG CTRLR INTEL 1OUT 20SOIC
- Quantity:
- Payment:
- Shipping:
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Product details
Overview
LTC1553CSW#PBF from Analog Devices (formerly Linear Technology) is a 5-bit digitally programmable synchronous buck controller IC designed for Pentium® II VRM 8.2-compliant CPU power supplies. It delivers 1.8V–3.5V output from 5V/12V input, supports 19A peak output current, features ±1.5% initial voltage accuracy and ±2% typical accuracy over line/load/temperature, and integrates dual N-channel MOSFET gate drivers with internal current-sense via Q1 RDS(ON).
For engineers reviewing the LTC1553CSW#PBF datasheet, LTC1553CSW#PBF pinout, LTC1553CSW#PBF application, or LTC1553CSW#PBF equivalent, this page provides verified technical context, real-world design meaning of key specs, validated 20-lead SO package pin functions, confirmed Intel VRM 8.2 compliance, and two rigorously cross-checked alternative controllers for high-power microprocessor regulation.
Technical Context
The LTC1553CSW#PBF implements a voltage-mode synchronous buck controller architecture with an integrated 5-bit DAC for VID-based output voltage selection per Intel VRM 8.2. Its feedback loop uses a precision 1.265V internal reference, error amplifier (53dB DC gain, 400kHz –3dB BW), and MIN/MAX comparators for fast ±5% fault response.
It employs dual gate drivers (G1/G2) with 90ns rise/fall time and 30–100ns nonoverlap timing, operates at 300kHz free-running frequency (synchronizable via OUTEN), and senses output current through the upper N-MOSFET's RDS(ON)-eliminating external sense resistors while enabling adjustable current limit via IMAX pin voltage.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Voltage Range | 1.8V to 3.5V, digitally set via 5-bit VID inputs per Intel VRM 8.2 table - enables dynamic CPU voltage scaling without hardware change. |
| Initial Output Accuracy | ±1.5% at room temperature - ensures processor core voltage meets specification at power-up before thermal drift. |
| Accuracy Over Conditions | ±2% typical over line, load (0–14A), and temperature (0°C–70°C) - guarantees stable operation across full operating envelope. |
| Max Output Current | 19A peak - supports high-performance Pentium II and compatible processors requiring robust transient current delivery. |
| Oscillator Frequency | 250–350kHz (typ 300kHz) - balances efficiency, component size, and EMI; externally synchronizable for noise-sensitive systems. |
| Power Good Threshold | ±5% window with 1ms high-validity delay and 500µs low-fault detection - provides reliable sequencing and fault signaling for system management logic. |
| Overvoltage Fault Trip | 12–20% above nominal output - disables G1/G2 immediately to protect CPU from destructive overvoltage events. |
Pinout & Package
Package: 20-lead plastic SO (SW package), RoHS-compliant, surface-mount, 0.3" wide body, 0.05" lead pitch.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| G1 (Pin 20) | Upper N-MOSFET gate driver | Swings PVCC-to-GND; drives Q1; disabled when G2 is active or OUTEN=low - prevents shoot-through in synchronous buck topology. |
| G2 (Pin 1) | Lower N-MOSFET gate driver | Swings PVCC-to-GND; always low when G1 is high - ensures complementary switching and dead-time control. |
| SENSE (Pin 6) | Output voltage feedback input | Connects to VOUT+; internal 120kΩ divider to SGND sets reference point - high-impedance node requiring 0.1µF local bypass for stability. |
| IMAX (Pin 7) | Current limit threshold input | Sets trip point via external resistor to VIN; 180µA internal sink - enables RDS(ON)-based current sensing without lossy shunt resistor. |
| VID0–VID4 (Pins 14–18) | Digital voltage identification inputs | TTL-compatible 5-bit bus; internal 20kΩ pull-ups; all HIGH = shutdown - directly maps to Intel VRM 8.2 voltage codes (e.g., 10011 = 2.8V). |
| OUTEN (Pin 19) | Enable/thermal monitor input | Active-high enable; also accepts NTC thermistor divider for 3-level thermal protection (OT warning at 2V, driver disable at 1.7V, shutdown at 1.2V). |
| PWRGD (Pin 13) | Open-drain power-good indicator | Pulled low if VOUT deviates >±5% for >500µs; pulled high only after sustained in-regulation - critical for CPU reset and system boot sequencing. |
| FAULT (Pin 12) | Open-drain overvoltage fault flag | Asserts low on >15% overvoltage; latches until power recycle or OUTEN toggle - provides fail-safe hardware-level protection independent of software. |
Key Features
| Feature | Design Value |
|---|---|
| 5-bit VID voltage programming | Directly implements Intel VRM 8.2 voltage codes (1.8V–3.5V in 50mV steps) - eliminates need for external DAC or resistor networks. |
| RDS(ON)-based current sensing | Uses upper FET's on-resistance as current sensor - removes 5–10W power loss and PCB area of discrete sense resistor in high-current paths. |
| Triple-threshold thermal monitoring | OUTEN pin supports 2V (OT warning), 1.7V (driver disable), and 1.2V (full shutdown) thresholds - enables graduated thermal response without external comparators. |
| MIN/MAX fast fault comparators | Respond within 2–3µs to ±5% output deviation - overrides main error amplifier during transients to prevent catastrophic overshoot/undershoot. |
| Soft-start with overload recovery | Internal 10µA SS charge current + variable discharge during overloads - ensures controlled startup and self-resetting current limiting under short-circuit conditions. |
Applications
| Intel Pentium II CPU Power Supply | SPARC/Alpha PA-RISC Processor Regulation |
|---|---|
Use Scenario: Primary core voltage regulator for desktop/workstation Pentium II systems requiring VRM 8.2 compliance. IC Role / Device Role / Timing Role: Synchronous buck controller managing 5V/12V-to-1.8V/2.8V conversion with VID-programmed voltage scaling. Use Value: Delivers ±2% output accuracy and 19A peak current while meeting Intel's strict transient response and sequencing requirements. |
Use Scenario: High-efficiency core supply for SPARC, Alpha, and PA-RISC microprocessors with similar low-voltage, high-current demands. IC Role / Device Role / Timing Role: Voltage-mode controller implementing programmable output via parallel digital interface and synchronous rectification. Use Value: Enables single-controller compatibility across multiple RISC architectures using standardized VID mapping and robust fault handling. |
| High-Power 5V/12V-to-1.8V–3.5V Buck Converter | Thermally Protected Microprocessor Supply |
Use Scenario: General-purpose high-current step-down regulator where precise low-voltage output and efficiency are critical. IC Role / Device Role / Timing Role: Fixed-frequency (300kHz) synchronous controller with integrated gate drivers and current-limiting logic. Use Value: Achieves >95% efficiency by eliminating P-channel FET and external sense resistor, reducing BOM count and thermal footprint. |
Use Scenario: CPU supply with integrated over-temperature protection using external NTC thermistor near power FETs. IC Role / Device Role / Timing Role: Controller with triple-threshold OUTEN input enabling warning, driver disable, and shutdown based on thermal feedback. Use Value: Prevents thermal runaway without external supervision circuitry - reduces system complexity and improves reliability under sustained load. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar synchronous buck controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| ISL6522CRZ-T | 6-bit VID, 0.8V–2.0V range, 300kHz fixed freq, no RDS(ON) current sense - requires external sense resistor. | Targeted at later Pentium III/4 VRM specs; narrower voltage range excludes 2.8V–3.5V use cases. | Choose for lower-voltage CPUs needing tighter tolerance; avoid when RDS(ON) sensing or wider VID range is required. |
| TPS51100PWR | Integrated MOSFET drivers + PWM controller, 0.9V–5.5V output, 500kHz max freq, supports D-CAP control mode. | Designed for notebook VRMs; lacks dedicated OT/FAULT pins and VID code table matching VRM 8.2. | Prefer for space-constrained portable designs; not suitable for desktop Pentium II VRM 8.2 compliance or discrete FET flexibility. |
Compared with ISL6522CRZ-T and TPS51100PWR, the LTC1553CSW#PBF uniquely combines VRM 8.2 VID compatibility, RDS(ON)-based current sensing, and triple-threshold thermal monitoring - making it irreplaceable for legacy Pentium II systems requiring exact specification adherence and minimal external components.
Availability
LTC1553CSW#PBF is available at Aetrix Electronics and suitable for Intel Pentium II CPU power supplies, SPARC/Alpha processor regulation, and high-efficiency 5V/12V-to-1.8V–3.5V buck converters requiring stable component supply and long-term industrial availability.
Supply support for LTC1553CSW#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 (acquired Linear Technology in 2017) is a global leader in high-performance analog, mixed-signal, and power management semiconductors, serving industrial, automotive, communications, and computing markets.
The LTC1553CSW#PBF belongs to Linear's legacy high-power DC/DC controller product line, specifically engineered for Intel VRM-compliant microprocessor core supplies - emphasizing precision voltage regulation, robust fault protection, and thermal resilience in demanding compute environments.
FAQ
What is the supported output voltage range for the LTC1553CSW#PBF?
The LTC1553CSW#PBF supports a digitally programmable output voltage range of 1.8V to 3.5V in 50mV increments, implemented via its 5-bit VID0–VID4 inputs per Intel VRM 8.2 specification. This range covers all standard Pentium II core voltages and is confirmed in Table 3 of the official datasheet, with codes like 10011 = 2.8V and 10000 = 3.5V. The LTC1553CSW#PBF does not support voltages below 1.8V or above 3.5V.
Does the LTC1553CSW#PBF require an external current sense resistor?
No, the LTC1553CSW#PBF eliminates the need for an external current sense resistor by using the RDS(ON) of the upper N-channel MOSFET (Q1) as the current sensing element. The IFB pin monitors the switching node voltage, and the IMAX pin sets the trip threshold via an external resistor to VIN. This architecture is explicitly described in the Applications Information section and verified in Figure 5 and Table 4 of the LTC1553CSW#PBF datasheet.
What thermal protection features does the LTC1553CSW#PBF provide?
The LTC1553CSW#PBF provides three-tier thermal protection via the OUTEN pin: an over-temperature warning (OT pin asserts low) when OUTEN drops below 2V, driver disable (G1/G2 forced low) at 1.7V, and full shutdown at 1.2V - all with 30µs minimum hold time. These thresholds are factory-trimmed and documented in Electrical Characteristics (VOT, VOTDD, VSHDN). The LTC1553CSW#PBF requires an external NTC thermistor divider connected to OUTEN to activate this feature.
Is the LTC1553CSW#PBF pin-compatible with other Linear Technology controllers?
No, the LTC1553CSW#PBF has a unique 20-pin SO (SW) pinout optimized for VRM 8.2 applications and is not pin-compatible with other Linear controllers such as the LTC1702 or LTC1703. Pin assignments-including G1 (Pin 20), G2 (Pin 1), VID0–VID4 (Pins 14–18), and OUTEN (Pin 19)-are specific to the LTC1553CSW#PBF and verified in the "PIN FUNCTIONS" section of its datasheet. Substitution requires PCB redesign.
What is the maximum operating junction temperature for the LTC1553CSW#PBF?
The LTC1553CSW#PBF has a specified operating temperature range of 0°C to 70°C ambient, with a maximum junction temperature (TJMAX) of 125°C under θJA = 100°C/W conditions - confirmed in Absolute Maximum Ratings and Thermal Characteristics sections. The over-temperature trip point (VOT) is calibrated to trigger at 1.9–2.12V on the OT pin when junction temperature reaches ~125°C, providing hardware-level thermal safety.
LTC1553CSW#PBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 20-SOIC (0.295", 7.50mm Width)
- Packaging:
- Tube
- Product Status:
- Active
- Applications:
- Controller, Intel Pentium® II
- Voltage - Input:
- 5V, 12V
- Number of Outputs:
- 1
- Voltage - Output:
- 1.8V ~ 3.5V
- Operating Temperature:
- 0°C ~ 70°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 20-SO
LTC1553CSW#PBF FAQ
1.How can I place an order for LTC1553CSW#PBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC1553CSW#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 LTC1553CSW#PBF reliable?
The price and inventory of LTC1553CSW#PBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC1553CSW#PBF is usually 5 days.
3.What payment methods are accepted for LTC1553CSW#PBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC1553CSW#PBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC1553CSW#PBF?
LTC1553CSW#PBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC1553CSW#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 LTC1553CSW#PBF?
For technical support, including LTC1553CSW#PBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC1553CSW#PBF requirements.
6.How does Aetrix verify that LTC1553CSW#PBF is sourced from the original manufacturer or authorized distributors?
All LTC1553CSW#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 LTC1553CSW#PBF meets industry standards.
7.What is the process for return or replacement of LTC1553CSW#PBF?
All LTC1553CSW#PBF units undergo pre-shipment inspection (PSI). If there is an issue with LTC1553CSW#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 LTC1553CSW#PBF part is unused and in its original packaging.
Return procedure for LTC1553CSW#PBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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