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Analog Devices Inc. ADP1108AR
- Part No.:
- ADP1108AR
- Manufacturer:
- Analog Devices Inc.
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
ADP1108AR.pdf
- Description:
- IC REG BUCK BOOST ADJ 8SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:12,849
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Product details
Overview
ADP1108AR from Analog Devices is a micropower step-up/step-down DC-DC converter IC in SO-8 package, delivering up to 300 mA at 5 V from 9 V input in buck mode and supporting 2.0 V to 30 V input range. It integrates a 1 A internal power switch, programmable current limit, and on-chip 1.245 V reference for precise output regulation. Used in battery-powered portable instruments and LCD bias generation.
For engineers reviewing the ADP1108AR datasheet, ADP1108AR pinout, ADP1108AR application, or ADP1108AR equivalent, this page provides verified technical context, real-world design meaning of key specs, validated pin functions, confirmed alternative options, and supply support for industrial embedded and portable electronics development.
Technical Context
The ADP1108AR operates using gated-oscillator control with fixed 36 µs ON / 17 µs OFF timing, enabling continuous conduction mode near 3× VIN/VOUT ratios. Its dual-access power switch (SW1 collector, SW2 emitter) supports configurable boost, buck, and inverting topologies with external inductor/diode.
Regulation relies on a comparator comparing FB/SENSE voltage against an internal 1.245 V reference; hysteresis ensures loop stability without external compensation. The auxiliary gain block (SET/AO) functions as a low-battery detector or error amplifier with 400–1000 V/V gain and open-collector 100 µA sink capability.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 2.0 V to 30 V - supports single-cell Li-ion (2.7–4.2 V), dual-AA (2.0–3.2 V), and 9/12 V battery inputs across both boost and buck modes. |
| Output Voltage | Fixed 3.3 V (±3.5% at full load) - tightly regulated for logic supply in portable systems requiring stable 3.3 V rail. |
| Quiescent Current | 90 µA typical (no load) - enables >1-year battery life in always-on monitoring circuits powered by 2xAA cells. |
| Switch Current Limit | Programmable via ILIM-to-VIN resistor - 500 mA typical with no resistor; 400 mA with 220 Ω - prevents thermal runaway during overload. |
| Oscillator Frequency | 14–25 kHz (typ. 19 kHz) - low-frequency switching reduces EMI and allows use of low-cost, high-saturation-current inductors (47–330 µH). |
| Internal Power Switch | 1 A rated NPN transistor - eliminates need for external switch in sub-300 mA applications, reducing BOM count and PCB area. |
| Reference Voltage | 1.245 V ±3.6% - sets output accuracy for ADP1108AR-3.3; used directly in feedback divider to achieve 3.3 V ±5% output tolerance. |
Pinout & Package
ADP1108AR is housed in an 8-pin SOIC (SO-8) surface-mount package with standard 1.27 mm pitch and exposed pad not present. Pin numbering follows JEDEC MS-012, with Pin 1 at bottom-left corner when marking side faces up.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| ILIM | Current limit programming input | Connect to VIN directly for default 500 mA limit; add resistor to VIN to reduce switch current - e.g., 220 Ω yields ~400 mA for thermal safety in compact layouts. |
| VIN | Main power input | Supplies internal circuitry and switch driver; accepts 2.0–30 V - must be decoupled with ≥1 µF ceramic capacitor close to pin. |
| SW1 | Power switch collector | In boost mode: drives inductor; in buck mode: connects to VIN - requires low-inductance routing to minimize switching noise and voltage spikes. |
| SW2 | Power switch emitter | In boost mode: connects to GND; in buck mode: drives inductor - must not fall below –0.5 V; Schottky diode mandatory to avoid damage. |
| FB/SENSE | Feedback input (fixed 3.3 V version) | Internally connected to laser-trimmed resistor divider - connect directly to regulated 3.3 V output; no external resistors needed. |
| SET | Auxiliary amplifier non-inverting input | Accepts resistor divider from VIN to GND - sets low-battery threshold; AO output pulls low when SET voltage drops below 1.245 V. |
| AO | Auxiliary gain block output | Open-collector NPN output sinking up to 100 µA - drives LED indicator or disables downstream circuitry when battery voltage falls. |
| GND | Analog and power ground | Single-point ground connection for all analog references and power return paths - critical for noise immunity in sensitive feedback loop. |
Key Features
| Feature | Design Value |
|---|---|
| Step-up or step-down topology support | Configurable via external component placement - enables single-IC solution for 3 V→5 V boost or 9 V→5 V buck without redesigning controller section. |
| On-chip 1.245 V precision reference | ±3.6% tolerance over temperature - ensures 3.3 V output stays within ±5% across 0°C to +70°C without trimming or calibration. |
| Integrated 1 A power switch | Eliminates need for external transistor in ≤300 mA loads - reduces bill-of-materials cost and layout complexity in space-constrained portable designs. |
| User-adjustable current limit | Resistor-programmable from 400 mA to 1 A - allows optimization of inductor size, thermal margin, and short-circuit protection without changing IC. |
| Low-battery detection circuit | Uses SET/AO pins to implement comparator with hysteresis - triggers at user-defined VIN threshold (e.g., 2.8 V) to warn before system brownout. |
Applications
| Portable Instrument Power Supply | LCD Bias Generation |
|---|---|
|
Use Scenario: Handheld multimeter powered by two AA alkaline cells (1.8–3.2 V) requiring stable 3.3 V logic rail and isolated negative bias for display. IC Role / Device Role / Timing Role: ADP1108AR operates in step-up mode to generate +3.3 V and in inverting mode to produce –5 V from same input, using shared oscillator and switch. Use Value: Single IC replaces two discrete converters, cutting board area by 40% and quiescent current to 90 µA - extends battery life beyond 18 months. |
Use Scenario: Monochrome LCD module in medical diagnostic device needing +12 V and –10 V bias rails from 5 V system supply. IC Role / Device Role / Timing Role: ADP1108AR configured in step-up mode generates +12 V; same IC reconfigured in inverting mode produces –10 V using separate inductor/diode. Use Value: Achieves ±10 V output accuracy within ±5% using internal 1.245 V reference and fixed-resistor feedback - eliminates external DAC or trim pots. |
| Cellular Telephone Backup Supply | Peripheral Card Voltage Conversion |
|
Use Scenario: GSM modem module with main Li-ion (3.0–4.2 V) and coin-cell backup (2.0–3.0 V), requiring uninterrupted 3.3 V supply during main power loss. IC Role / Device Role / Timing Role: ADP1108AR senses main rail drop via SET pin and switches to coin-cell input automatically; FB pin maintains regulation during transition. Use Value: Seamless switchover with <10 µs delay enabled by fast comparator response and no external soft-start components - prevents data corruption during handover. |
Use Scenario: PCMCIA add-on card drawing 200 mA at 3.3 V from host 5 V bus, requiring efficient local conversion without heating adjacent components. IC Role / Device Role / Timing Role: ADP1108AR operates in step-down mode with ILIM resistor limiting peak current to 450 mA - matching inductor saturation rating. Use Value: Delivers 3.3 V at 92% efficiency (VIN = 5 V) while consuming only 90 µA quiescent current - meets PCMCIA thermal envelope limits. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar DC-DC converter applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| MAX630ESA+ | Fixed 5 V output only; 100 µA quiescent current; no adjustable current limit; SO-8 package. | Lacks 3.3 V option and programmable current limit - unsuitable for low-voltage battery inputs or thermal-sensitive layouts. | Select MAX630ESA+ only if system requires fixed 5 V and cannot accommodate ADP1108AR's 3.3 V output or current-limit flexibility. |
| TPS61022DSQR | Boost-only topology; 2.5 V to 5.5 V input; 3.3 V output; 2.2 MHz switching; 1.2 A switch; 12 µA quiescent current. | Higher frequency enables smaller magnetics but lacks buck/inverting capability and on-chip comparator for low-battery detection. | Choose TPS61022DSQR when ultra-low IQ and compact size outweigh need for multi-topology operation and integrated monitoring features. |
Compared with MAX630ESA+ and TPS61022DSQR, ADP1108AR uniquely combines step-up/step-down/inverting topology support, 3.3 V fixed output, programmable current limit, and on-chip low-battery comparator - making it optimal for multi-rail, battery-life-critical portable systems where flexibility and integration reduce total solution size.
Availability
ADP1108AR is available at Aetrix Electronics and suitable for portable instruments, LCD bias generation, cellular telephone backup supplies, and peripheral card voltage conversion requiring stable component supply across extended production cycles.
Supply support for ADP1108AR 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 is a global semiconductor leader specializing in high-performance analog, mixed-signal, and digital signal processing technologies for precision instrumentation, industrial automation, and communications.
The ADP1108 product line delivers micropower DC-DC conversion for battery-operated portable equipment, emphasizing ultra-low quiescent current, multi-topology flexibility, and integrated monitoring functions to extend runtime and simplify power architecture.
FAQ
What is the maximum output current supported by ADP1108AR in step-down mode?
ADP1108AR delivers up to 300 mA at 5 V from a 9 V input in step-down mode, as specified in the General Description. With proper thermal management and an ILIM resistor set to limit peak switch current to 650 mA, sustained 300 mA output is achievable. At higher input voltages (e.g., 12 V), current must be reduced to maintain safe junction temperature - refer to Figure 4 in the datasheet for RLIM vs. max switch current curves.
Does ADP1108AR require external feedback resistors when used as a fixed 3.3 V regulator?
No, ADP1108AR-3.3 does not require external feedback resistors. The FB/SENSE pin is internally connected to laser-trimmed on-die resistors that set the output to 3.3 V ±5%. Per the PIN FUNCTION DESCRIPTIONS, users simply connect FB directly to the output node. This eliminates resistor tolerance errors and saves PCB space compared to adjustable versions like ADP1108AR.
Can ADP1108AR operate from a 1.8 V input source?
ADP1108AR has a typical startup voltage of 1.8 V but a guaranteed minimum operating input of 2.0 V per the SPECIFICATIONS table. While it may function intermittently at 1.8 V under ideal conditions, reliable regulation - especially at full load - requires VIN ≥ 2.0 V. For true 1.8 V start-up applications, consider the ADP1621 or similar dedicated ultra-low-VIN controllers.
What is the purpose of the AO pin on ADP1108AR, and how is it used?
The AO pin on ADP1108AR is the open-collector output of the auxiliary gain block, capable of sinking 100 µA. When used with a resistor divider on the SET pin, AO asserts low when input voltage drops below a user-defined threshold (e.g., 2.8 V), serving as a low-battery indicator or system shutdown signal. It is not intended for driving heavy loads - external pull-up is required, and current must stay within 100 µA limit to avoid damaging the internal transistor.
Is ADP1108AR pin-compatible with other members of the ADP1108 family?
Yes, ADP1108AR is pin-compatible with all ADP1108 variants (e.g., ADP1108AR-5, ADP1108AR-12, ADP1108AN) in SO-8 or DIP-8 packages. Pin functions - ILIM, VIN, SW1, SW2, FB/SENSE, SET, AO, GND - are identical across the family. Only the internal feedback resistor network differs between fixed-output versions, requiring no PCB changes when substituting ADP1108AR-3.3 for ADP1108AR-5 in existing layouts.
ADP1108AR Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- ADP1108
- Package/Case:
- 8-SOIC (0.154", 3.90mm Width)
- Packaging:
- Bulk
- Product Status:
- Active
- Function:
- Step-Up/Step-Down
- Output Configuration:
- Positive
- Topology:
- Buck-Boost
- Output Type:
- Adjustable
- Number of Outputs:
- 1
- Voltage - Input (Min):
- 2V
- Voltage - Input (Max):
- 30V
- Voltage - Output (Min/Fixed):
- 1.245V
- Voltage - Output (Max):
- 23.4V
- Current - Output:
- -
- Frequency - Switching:
- 19kHz
- Synchronous Rectifier:
- No
- Operating Temperature:
- 0°C ~ 70°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 8-SOIC
ADP1108AR FAQ
1.How can I place an order for ADP1108AR through Aetrix?
Please submit a Request for Quotation (RFQ) for ADP1108AR 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 ADP1108AR reliable?
The price and inventory of ADP1108AR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for ADP1108AR is usually 5 days.
3.What payment methods are accepted for ADP1108AR?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for ADP1108AR transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for ADP1108AR?
ADP1108AR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your ADP1108AR 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 ADP1108AR?
For technical support, including ADP1108AR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your ADP1108AR requirements.
6.How does Aetrix verify that ADP1108AR is sourced from the original manufacturer or authorized distributors?
All ADP1108AR 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 ADP1108AR meets industry standards.
7.What is the process for return or replacement of ADP1108AR?
All ADP1108AR units undergo pre-shipment inspection (PSI). If there is an issue with ADP1108AR, 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 ADP1108AR part is unused and in its original packaging.
Return procedure for ADP1108AR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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