In modern power systems, efficient, flexible and reliable power management chips are at the heart of all types of industrial and consumer electronic devices. As a high-performance two-way synchronous buck-boost controller, CXLB73329 not only supports a wide voltage input and output range of 3.6V to 32V, but also has multi-cell battery management, intelligent charge and discharge control and comprehensive system protection functions. It is suitable for various scenarios such as automobiles, industry, backup power supply and USB PD. This article will systematically introduce the technical characteristics, pin functions, working modes and typical applications of the CXLB73329 to help engineers realize high-performance power supply design.
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[ CXLB73329 ]"
In modern power systems, efficient, flexible and reliable power management chips are at the heart of all types of industrial and consumer electronic devices. As a high-performance two-way synchronous buck-boost controller, CXLB73329 not only supports a wide voltage input and output range of 3.6V to 32V, but also has multi-cell battery management, intelligent charge and discharge control and comprehensive system protection functions. It is suitable for various scenarios such as automobiles, industry, backup power supply and USB PD. This article will systematically introduce the technical characteristics, pin functions, working modes and typical applications of the CXLB73329 to help engineers realize high-performance power supply design.
1. chip overview and core technology characteristics
The CXLB73329 is a four-switch bi-directional synchronous buck-boost controller that operates stably in buck, boost, and buck-boost modes for bi-directional control of battery charge and discharge. Its core features include:
· Support 1 to 6 battery charge and discharge management, battery type and voltage can be flexibly set by external resistor;
· Wide input and output voltage range: 3.6V-32V (maximum 36V);
· Integrated 2A peak current MOSFET gate driver for high efficiency power conversion;
· Switching frequency programmable: 150kHz, 300kHz, 600kHz, 1200kHz, to adapt to different efficiency and size requirements;
· Support analog voltage or PWM signal dynamic programming output voltage and current limit;
· Built-in 55mA low quiescent current LDO, continuous power supply for system MCU;
· Input/output under-voltage protection, over-voltage protection, cycle-by-cycle current limit, thermal shutdown and output short-circuit protection;
· Compact QFN4 × 4-32 package for high-density PCB layouts.
2. Pin Function and System Structure
CXLB73329 32 functional pins are available, key pins include:
· VADJ/IADJ: Output voltage/current limit programming pin, support 0-2V analog voltage or PWM signal;
· VSET: Battery type setting (such as 4.2V/4.35V/4.4V/4.5V, etc.);
· VREF/IREF: Voltage/current control loop reference voltage;
· BRCOMP: Battery internal resistance compensation pin, used for voltage compensation during high current charging;
· LDO: 5V/55mA output, can power external MCU;
· STAT: Charging status indication/PGOOD signal output;
· FREQ: Switching frequency setting pin;
· FB2: VBUS voltage feedback, used for output voltage setting in discharge mode;
· CSP1/CSN1、CSP2/CSN2Input/output current sampling;
· EN: Chip enable control, internal pull up to 4V;
· OTG: Charge and discharge mode selection (low level is charging, high level is discharging);
· TS: Battery temperature detection;
· CELLS: Battery series number setting.
3. working mode and control mechanism
3.1. Charging mode (OTG = Low)
In the charging mode, the CXLB73329 is used as a synchronous buck-boost charging controller to support complete current elimination & rarr; constant current & rarr; constant voltage charging process:
· current elimination charging: Start when the battery voltage is lower than 3V and pre-charge with small current;
· constant current charging: After the battery voltage exceeds the current elimination threshold, charge quickly according to the set current;
· constant voltage charging: When the battery voltage is close to the set value, it turns to the constant voltage stage, and the current gradually decreases;
· Charge cut-off and recharging: Stop charging when the current is lower than the termination current; restart automatically when the voltage falls back to the recharge threshold.
3.2. Discharge mode (OTG = High)
In the discharge mode, the chip boosts or lowers the battery energy and outputs it from VBUS. The output voltage can be set by external resistor voltage division of FB2 pin or programming of VADJ pin, supporting fast charging protocols such as USB PD.
Detailed explanation of 4. key functions
4.1. Frequency setting and dithering
Four switching frequencies (150kHz-1200kHz) can be set through the FREQ pin. The high frequency is suitable for small-size inductors, and the low frequency is suitable for high-efficiency scenarios. The chip supports frequency jitter function to effectively improve EMI performance.
4.2. Current Limiting and Protection
CXLB73329 support cycle-by-cycle peak current limit and average current limit, the limit threshold can be set through an external sampling resistor. When an overcurrent or short circuit is detected, the chip enters a hiccup mode, reducing system power consumption and thermal risk.
4.3. Battery internal resistance compensation
Through the external resistor of the BRCOMP pin, the voltage compensation of the internal resistance of the battery can be realized, and the constant voltage charging accuracy can be improved, especially in the high-current charging scenario.
4.4. Thermal Management and Other Protection
The chip has a thermal shutdown function (threshold 160°C, hysteresis 20°C) and supports external temperature detection at the TS pin to ensure that the battery works within a safe temperature range. In addition, it also provides input/output UVLO, OVP and other multiple protection.
5. typical application scenarios
CXLB73329 are ideal for the following applications:
· car start-stop system: Support wide voltage input to adapt to car battery voltage fluctuations;
· Industrial PC and Standby Power SupplyHigh reliability and multiple protection;
· USB PD adapter and mobile power: Support bidirectional power flow and fast charging protocol;
· Super Capacitor and Multi-cell Battery Management System: Flexible support 1-6 string battery pack;
· Industrial test equipment and communication power supplyWide voltage range with programmable output.
6. Design Essentials and External Component Selection
6.1. Inductor Selection
The inductance value is selected according to the operating frequency and ripple requirements. Ferrite or shielded inductance is recommended to reduce magnetic loss and radiation noise. The inductor saturation current needs to be higher than the peak current with sufficient margin.
6.2. Current sampling resistor
It is recommended to use high-precision, low-temperature drift metal film resistors, and use Kelvin connection mode during layout to ensure sampling accuracy.
6.3. Input output capacitance
Low ESR MLCC or polymer capacitors are selected and arranged in parallel to meet ripple and RMS current requirements. It is recommended to place the decoupling capacitor near the VBAT/VBUS pin.
6.4. MOSFET Selection
N-channel power MOSFETs are selected based on voltage and current levels, focusing on on-resistance RDS(on), gate charge Qg, and reverse transfer capacitance Crss to optimize switching losses and efficiency.
7. PCB Layout Recommendations
Good PCB layout is critical to performance:
· The feedback network (R1/R2) should be close to the FB2 pin and away from the power node;
· Current sampling lines are arranged symmetrically, away from high frequency noise sources such as SW and BST;
· The power circuit (VBAT/VBUS, SW, GND) should be short and wide to reduce parasitic parameters;
· The inductor and switch node are as close to the chip as possible to reduce radiation interference.
8. epilogue
With its wide voltage range, high integration, flexible programming capability and comprehensive protection functions, the CXLB73329 provides a reliable single-chip solution for bidirectional buck-boost power supply systems. Whether in automotive, industrial or consumer electronics, the chip helps designers achieve efficient, compact and safe power architectures.
JTM-IC（jtm-ic.com) As a professional integrated circuit solution provider, we are committed to providing customers with high-performance, high-reliability chip products and complete technical support. For CXLB73329 samples, technical information or design assistance, please visit our official website or contact the technical support team.
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