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Analog Devices Inc. LTC1504CS8
- Part No.:
- LTC1504CS8
- Manufacturer:
- Analog Devices Inc.
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
LTC1504CS8.pdf
- Description:
- IC REG BUCK ADJ 500MA 8SO
- Quantity:
- Payment:
- Shipping:
Inventory:3,463
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Product details
Overview
LTC1504CS8 from Analog Devices (formerly Linear Technology) is an adjustable-output, synchronous buck DC/DC switching regulator IC delivering up to 500mA at 3.3V from a 4V–10V input. It integrates dual 1.5Ω on-chip MOSFETs, features a 1.265V ±1% internal reference, 200kHz fixed-frequency operation (synchronizable to 500kHz), and active current sinking capability for tight output regulation in portable digital systems.
For engineers reviewing the LTC1504CS8 datasheet, LTC1504CS8 pinout, LTC1504CS8 application, or LTC1504CS8 equivalent, key selection considerations include its SO-8 package thermal performance (θJA = 90°C/W), FB pin servoing to 1.265V, adjustable current limit via IMAX resistor, soft-start control via external capacitor on SS, and compatibility with low-ESR ceramic or tantalum output capacitors in space-constrained designs.
Technical Context
The LTC1504CS8 implements a synchronous buck topology with integrated P-channel high-side and N-channel low-side MOSFETs, enabling bidirectional output current flow (source/sink) for improved transient response and reduced dropout under load steps. Its feedback loop uses a transconductance error amplifier (gmV = 350–1100 µmho, AV = 40–48 dB) referenced to a trimmed 1.265V bandgap, with fast-acting MIN/MAX comparators enforcing ±3% output window limits independent of the main loop.
Current limiting is implemented via an ILIM amplifier comparing SW-to-GND voltage drop across Q1 against a user-set threshold at IMAX (12µA sink current), dynamically modulating COMP through SS to reduce duty cycle. The oscillator operates at 200kHz nominal but reduces frequency under severe overload to maintain control-down to ~20kHz during hard shorts-while thermal shutdown protects at TJMAX = 115°C.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Current | 500mA continuous at 3.3V; limited by SO-8 thermal resistance (90°C/W) and ambient layout |
| Input Voltage Range | 4V to 10V; not guaranteed below 4V without factory consultation |
| Feedback Voltage | 1.265V ±1% (typical); sets output via external resistor divider on FB pin |
| Switching Frequency | 200kHz typical, adjustable 150–250kHz; synchronizable up to 500kHz |
| Peak Efficiency | 92% at 5V→3.3V/500mA; enabled by synchronous rectification and low RDS(on) switches |
| Internal Switch RON | 1.3–2.0Ω (combined high/low-side); defines conduction loss and thermal dissipation |
| Shutdown Current | <1µA when SHDN pulled low; SW actively driven low to prevent backfeed |
Pinout & Package
Package: 8-lead plastic SO (SO-8), 1504 marking, θJA = 90°C/W, TJMAX = 115°C. Exposed pad not present; GND pin (4) serves as primary thermal path.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| IMAX (1) | Current limit threshold set | 12µA internal sink current sets VIMAX; resistor from VCC determines trip point (e.g., 47kΩ → ~350mA) |
| VCC (2) | Main power supply input | 4V–10V input; requires local low-ESR ceramic bypass (≥1µF) adjacent to pin |
| SW (3) | Switch node output | Drives external inductor; peak current >±1A; avoid shorting to GND/VCC |
| GND (4) | Power and signal ground | Low-impedance return for input/output caps, feedback divider, and thermal dissipation |
| FB (5) | Feedback input (adjustable version) | Servo point for 1.265V reference; connect to resistor divider from VOUT to GND |
| SHDN (6) | Active-low enable control | Logic high ≥2.4V enables operation; logic low ≤0.8V drops supply current to <1µA |
| SS (7) | Soft-start and current-limit modulation | 12µA source pulls external cap; ILIM pulls it down during overloads to clamp COMP |
| COMP (8) | Error amplifier output | High-impedance node for external RC compensation; directly controls PWM duty cycle |
Key Features
| Feature | Design Value |
|---|---|
| Synchronous buck architecture | Enables output current sinking for fast negative load transients and reduced dropout |
| Integrated 1.5Ω MOSFETs | Eliminates external power devices; reduces BOM count and layout area vs controller-only solutions |
| 1% trimmed internal reference | Ensures ±1.5% total output accuracy over line/load/temperature without trimming |
| Dual-loop transient protection | MIN/MAX comparators override main loop within ±3% window for sub-microsecond fault correction |
| Adjustable current limit | Single-resistor programming (IMAX) avoids external sense resistor and associated power loss |
Applications
| Portable Digital Systems | Active Termination |
|---|---|
Use Scenario: Powering 3.3V I/O rails in handheld PDAs, GPS units, or battery-powered instrumentation where board space and quiescent current are critical. IC Role / Device Role / Timing Role: Primary step-down regulator converting 5V or 7.2V Li-ion battery-derived input to stable 3.3V logic supply. Use Value: 92% peak efficiency extends battery life; SO-8 footprint minimizes PCB area; shutdown current <1µA enables deep-sleep modes. | Use Scenario: Providing precise 3.3V termination voltage for high-speed parallel buses (e.g., SCSI, PCI-X stubs) requiring low-noise, fast transient response. IC Role / Device Role / Timing Role: Low-impedance, bidirectional current source/sink maintaining bus voltage during signal edge transitions. Use Value: Active sinking capability prevents overshoot/ringing; ±3% MIN/MAX comparators suppress >100ns transients without loop instability. |
| Auxiliary Output Voltage Supplies | Minimum Part Count/Size Switchers |
Use Scenario: Generating isolated 3.3V bias for analog front-ends, ADC references, or RF subsystems in multi-rail industrial controllers. IC Role / Device Role / Timing Role: Secondary regulated supply decoupled from main system rail, with independent enable/shutdown control. Use Value: SHDN pin allows synchronized power sequencing; FB pin enables custom output voltages (e.g., 2.5V, 1.8V) using standard resistors. | Use Scenario: Replacing linear regulators (e.g., LM1117) in cost-sensitive consumer electronics where efficiency and thermal constraints prohibit LDO use. IC Role / Device Role / Timing Role: Compact, self-contained switching solution requiring only four external components (CIN, COUT, L, feedback divider). Use Value: Eliminates need for external MOSFET drivers, current sense amps, or compensation ICs-reducing design time and validation risk. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar synchronous buck regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT1934ES5-3.3 | Fixed 3.3V output, SOT-23-5 package, 300mA rating, no IMAX/SS pins | Lower current, smaller footprint, no adjustable current limit or soft-start tuning | Select when 300mA suffices and board area is more constrained than feature flexibility |
| TPS62231DRVR | 3MHz switching, 600mA, DSBGA-6 package, integrated compensation, 2.5–6V input | Higher frequency enables smaller L/C, but lower max input voltage and no current limit adjustment | Select for ultra-compact layouts needing <1mm height and faster transient response, accepting trade-offs in input range and programmability |
Compared with LT1934ES5-3.3 and TPS62231DRVR, the LTC1504CS8 offers higher output current (500mA), wider input range (4–10V), and full programmability (FB, IMAX, SS, COMP), making it suitable for legacy industrial and portable systems where thermal headroom and design flexibility outweigh miniaturization goals.
Availability
LTC1504CS8 is available at Aetrix Electronics and suitable for portable digital systems, active termination circuits, auxiliary voltage supplies, and minimum-part-count switcher designs requiring stable component supply across extended production lifecycles.
Supply support for LTC1504CS8 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 and maintains full technical and supply chain support for legacy Linear products including the LTC series.
The LTC1504 belongs to Linear's precision monolithic switching regulator family, designed specifically for space-constrained, efficiency-critical applications in portable and industrial electronics where integration, thermal performance, and transient robustness are prioritized over ultra-high frequency or ultra-low quiescent current.
FAQ
What is the function of the FB pin on the LTC1504CS8?
The FB (Feedback) pin on the LTC1504CS8 is the servo input for the internal 1.265V reference voltage. It connects to the center tap of an external resistor divider between VOUT and GND, allowing precise setting of the output voltage (e.g., 3.3V, 2.5V, or 1.8V). The LTC1504CS8 feedback loop continuously adjusts the duty cycle to maintain 1.265V at the FB pin, ensuring tight regulation across line, load, and temperature variations. This differs from the LTC1504CS8-3.3 variant, which uses a SENSE pin tied internally to a fixed 3.3V divider.
Can the LTC1504CS8 operate with an input voltage below 4V?
The LTC1504CS8 is specified for 4V to 10V input operation per its absolute maximum and electrical characteristics tables. While the device may function at 3.3V or 2.7V in some conditions, Linear Technology explicitly states that guaranteed specifications-including output accuracy, current limit, and efficiency-are not assured below 4V. Customers requiring sub-4V operation must contact Analog Devices' factory for characterization data or consider alternative regulators such as the LTC3605 or TPS62130, as the LTC1504CS8 is not rated for reliable performance below its 4V minimum.
How does the current limit circuit work on the LTC1504CS8?
The LTC1504CS8 implements current limiting via the IMAX pin, which sources a precise 12µA internal current. A resistor from VCC to IMAX sets the voltage threshold; when the voltage drop across the internal high-side MOSFET (Q1) exceeds this threshold during conduction, the ILIM amplifier pulls current from the SS pin. This lowers the SS voltage, which clamps the COMP pin and reduces PWM duty cycle to limit output current. The external SS capacitor (typically 0.1µF) sets both soft-start ramp time and current-limit response speed. No external sense resistor is required.
What package type and thermal characteristics apply to the LTC1504CS8?
The LTC1504CS8 is supplied in an 8-lead plastic SO (SO-8) package marked "1504", with a junction-to-ambient thermal resistance (θJA) of 90°C/W under standard JEDEC 2-layer board conditions. Pin 4 (GND) serves as the primary thermal path; designers must maximize copper area connected to this pin to improve heat dissipation. The maximum junction temperature is 115°C. Unlike thermally enhanced packages, the SO-8 lacks an exposed pad, so layout-driven thermal management-especially grounding and copper pour-is essential to sustain 500mA output current reliably.
Is the LTC1504CS8 pin-compatible with the LTC1504CS8-3.3?
No, the LTC1504CS8 and LTC1504CS8-3.3 are not pin-compatible. Although both use the same SO-8 package and share identical pin numbering, Pin 5 functions as FB (feedback input) on the LTC1504CS8 but as SENSE (fixed 3.3V output sense) on the LTC1504CS8-3.3. Their internal reference networks differ: the LTC1504CS8 relies on an external resistor divider to set output voltage, while the LTC1504CS8-3.3 has an onboard 3.3V divider. Interchanging them without modifying the feedback network will result in incorrect or unregulated output voltage.
LTC1504CS8 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 8-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):
- 4V
- Voltage - Input (Max):
- 10V
- Voltage - Output (Min/Fixed):
- 1.265V
- Voltage - Output (Max):
- 9V
- Current - Output:
- 500mA
- Frequency - Switching:
- 200kHz
- Synchronous Rectifier:
- Yes
- Operating Temperature:
- 0°C ~ 70°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 8-SO
LTC1504CS8 FAQ
1.How can I place an order for LTC1504CS8 through Aetrix?
Please submit a Request for Quotation (RFQ) for LTC1504CS8 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 LTC1504CS8 reliable?
The price and inventory of LTC1504CS8 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LTC1504CS8 is usually 5 days.
3.What payment methods are accepted for LTC1504CS8?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LTC1504CS8 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LTC1504CS8?
LTC1504CS8 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LTC1504CS8 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 LTC1504CS8?
For technical support, including LTC1504CS8 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LTC1504CS8 requirements.
6.How does Aetrix verify that LTC1504CS8 is sourced from the original manufacturer or authorized distributors?
All LTC1504CS8 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 LTC1504CS8 meets industry standards.
7.What is the process for return or replacement of LTC1504CS8?
All LTC1504CS8 units undergo pre-shipment inspection (PSI). If there is an issue with LTC1504CS8, 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 LTC1504CS8 part is unused and in its original packaging.
Return procedure for LTC1504CS8:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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