IC1 Detailed Explanation
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IC1: IC1
Purpose & Key Functions
- Integrated Li-Ion linear charger and dynamic power-path manager for single-cell systems.
- Powers the system load while independently charging the battery (Dynamic Power-Path Management, DPPM).
- Reduces battery charge/discharge cycles, enables “instant-on” even with a discharged or absent battery.
- Automatically shares input current between battery charging and system supply, preventing adapter or USB port overload.
- Monitors battery temperature via TS pin (external NTC thermistor) to ensure safe charging.
Notable Characteristics
- Charge Current Set (ISET pin): Program with a single resistor to VSS for up to 1 A charge.
- Input Current Limit (ILIM pin): Sets maximum adapter or USB input current via resistor.
- Status Outputs:
- CHG (open-drain) indicates charging in progress.
- PGOOD (open-drain) signals when SYS output is within regulation.
- Thermal Regulation: On-chip thermal fold-back prevents overheating under high ambient or heavy load.
- Under-Voltage Lockout (UVLO): Ensures reliable startup; IN thresholds track USB-IF requirements.
- Fixed Regulated SYS Output: 4.4 V typical (VO(REG)) to power system rails.
Operation in a Circuit
- Adapter Plug-in: IN pin senses external power (USB or DC adapter).
- DPPM Control:
- If system load + charge current input limit, charge current is reduced to maintain system voltage.
- SYS Output: Always regulated to VO(REG), powering downstream circuitry.
- Battery Charging: Independent current-limited, three-phase linear charge (pre-charge, fast charge, termination) with safety timer.
- Thermistor Monitoring (TS): Suspends charge if battery temperature is outside safe window.
Common Applications
- Portable and handheld devices (smart sensors, wearables)
- USB-powered battery-backed systems
- “Always-on” embedded electronics requiring seamless battery backup
Family & Variations
The BQ2407x series comprises five pin-compatible devices:
Table
| Model | SYS Output Behavior | Special Features | Typical Use Case |
|---|---|---|---|
| BQ24072RGTT | VO(REG) = BAT + 200 mV clamp | Adjustable SYS above BAT | Systems requiring minimal SYS-BAT delta |
| BQ24073RGTT | Fixed VO(REG) | Standard DPPM | General purpose single-cell chargers |
| BQ24075RGTT | Fixed VO(REG) | Low quiescent current (standby ~35 µA) | Battery-backed “always-on” applications |
| BQ24074RGTT | Fixed VO(REG) | Functional-safety capable (IEC 61508) | Safety-critical and industrial systems |
| BQ24079RGTT | Fixed VO(REG) | Standby current < 1 µA | Ultra low-power, energy-harvesting devices |
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Key Differences:
- Output clamp behavior (fixed vs. BAT+200 mV).
- Standby/quiescent current levels for battery life optimization.
- Functional safety certifications on select models.
-
Typical Selection Guidance:
- Choose BQ24075 for low-power portable devices needing “instant on” and efficient standby.
- Use BQ24074 where IEC-compliance and safety diagnostics are required.
- Select BQ24072 if system rails must follow battery voltage with minimal offset.
All BQ2407x devices share the same 16-pin VQFN package and pinout, simplifying design reuse across variants.
Calculate ISET resistor
Decoupling cap values
NTC thermistor selection
Layout guideline check
347 days
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