In the fields of industrial control system, fast charging equipment and PC power supply, an efficient and stable DC-DC step-down solution is the core requirement. As a synchronous rectifier power management chip with wide voltage input, CXSD62685 has become an ideal choice for cost-effective power supply design due to its high current output capability over 20A and multiple protection mechanisms.
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[ CXSD62685 ]"
CXSD62685: high-performance synchronous rectification Buck power chip deep analysis
In the fields of industrial control system, fast charging equipment and PC power supply, an efficient and stable DC-DC step-down solution is the core requirement. CXSD62685 as a synchronous rectifier power management chip with wide voltage inputHigh current output capability above 20AAnd multiple protection mechanisms, becoming an ideal choice for cost-effective power supply design.
I. Core features and advantages
1. Wide voltage adaptability
a. Input voltage range10V-25V, the suspension voltage tolerance is as high80V
B. Built-in VCC voltage regulator design (10-15v recommended), can be used with 78L12 when input> 18V
2. Efficient synchronous rectification architecture
a. The efficiency of synchronous rectification scheme is increased by more than 15%
B. SupportCycle-By-Cycle throttling,Short circuit latch protection,155 ℃ temperature protectionTriple Protection
3. Flexible adjustable parameters
a. Adjust the PWM frequency through an external resistor:Fosc(KHz)=6150/RI
B. The dead time can be adjusted:DT(nS)=5*RT(51kohm resistance corresponds to 250nS)
c. Free setting of output voltage:Vout=(1 R1/R2)*1.3V
II. Key Circuit Design Guide
1. Power device selection
a.MOS tube needs to be metLow internal resistance low junction capacitanceFeatures
B. Peak current calculation:lpeak=0.19V/R3(External sampling)
2. Inductance and capacitance designMathematical formula
a. Inductance L = Vout ×(Vin-Vout) / (Vin × Fs × Iripple)
B. Output ripple & Delta;Vo = & Delta;IL ×(ESR +1/(8.5 × Fs × Co)) recommended ripple current ≤ 30% maximum output current
3. Key points of PCB layout
a.VCC/GND capacitor, VB/VS bootstrap capacitor requiredClose to chip pin
B. Large current pathShort and wide routing
3. Typical application scenarios
| Application Field | Solution advantages |
|---|---|
| Fast charging power supply | Support 12V/24V input adaptive |
| Industrial Control System | -45 ℃ ~ 125 ℃ wide temperature range operation |
| Inverter system | 90% high duty cycle output capability |
| PC auxiliary power supply | SSOP16 package saves 60% of board space |
IV. Security protection mechanism
1. Short circuit protection: trigger latching when the output voltage is less than 75%. Restart EN or VCC to recover
2. Intelligent drive control:
a.HO Pin control high-end MOS (withstand voltage 80V)
B. LO pin driver low-end MOS(VCC power supply)
3.IS pin monitors MOS overcurrent in real time, and the response speed IS less than 1 seconds
Packaging and electrical specifications
1.SSOP16 package: size 4.9 × 6.0 (typical), suitable for high density design
2. Standby power consumption:
a. On-state static current 1mA (typical)
B. Power consumption in off mode 0.6mA
Design Tips: in the 24V input system, we recommend that you use the figure 6-2Wide voltage application circuit, cooperate with external MOS to achieve 20A continuous output; 12V system can use Figure 6-1 built-in sampling scheme to reduce costs.
CXSD62685 greatly shorten the power development cycle by simplifying peripheral circuits (only 11 necessary components are required) and providing flexible parameter configuration. ItsPatented dead zone control technologyEffectively avoid MOS common phenomenon, combined with multi-layer protection design, provide safe and reliable power supply solution for industrial equipment. For complete specifications and design tools, please contact official technical support.
Component parameters and precautions in application design
The VCC power supply voltage is recommended to be 10-15V, which can effectively and completely open the internal power tube. If the input exceeds 18V, we recommend that you add a 78L12 to regulate the VCC of the chip.
2 Setting of switching frequency
The PWM switching frequency is set by connecting a resistor between the chip RI pin and GND. The specific frequency value can be determined by the following formula Fosc(KHz)= 6150/RI (kΩ)
3 Setting of dead time
A resistor is connected between the chip DT pin and GND to set the dead time. The specific dead time value can be determined by the following formula DT(nS)= 5 * RT (kΩ)
4 PCB board layoutThe capacitance between VCC and GND and the bootstrap capacitance between VB and VS should be as close as possible to the chip pin; The high-current path routing should be as wide and short as possible.
5 MOS tube selection:MOS tube select low internal resistance and low junction capacitance, which can provide good performance for CXSD62685 pressure reducer.
6 output inductance
CXSD62685 works in continuous mode. The inductance can be selected according to the following formula:
Where Vin is the input voltage, VoutIt is the output voltage, Fs is the PWM operating frequency, and Iripple is the peak-to-peak value of the current ripple in the inductor. Generally, Iripple is selected to not exceed the maximum output power.
30% of the stream.
7 output capacitor
The output capacitor Co is used to filter the output voltage so that DC-DC pressure reducer outputs relatively stable direct current to the load. Select this
When the capacitor is used, the capacitor with low ESR should be selected as much as possible. The size of the selected capacitor value is mainly determined by the ripple requirement of the output voltage, which can be determined by the following formula:
Where & Delta;Vo is the output voltage ripple, & Delta;IL is the inductor current ripple, Fs is the PWM operating frequency, and ESRIt is the equivalent series resistance of the output capacitor.
8 output voltage setting
The output voltage of CXSD62685 is set by two divider resistance on the FB pin, and the internal error amplifier reference voltage is 1.3V, as shown in Figure 8.5
As shown, the output voltage Vout =(1 R1/R2)* 1.3V. If you need to set the output voltage to 14.3V, you can set R1 to 10K,R2 to 1K, and output
Voltage Vout =(1 10/1)* 1.3V = 14.3V.
9 peak current limiting settingsCXSD62685 the peak current limit is determined by the current limiting resistor R3 parameter. The peak current Ipeak = 0.19V/R3.
10 short circuit protection function
When the output is over-current, the output voltage is lower than three quarters of the output setting voltage, and the internal detection delay of the chip enters the short circuit protection.
The outbound power tube is closed. The output can only be restored if the chip VCC is powered on again or the EN pin is re-enabled and triggered.
Technical Specification (product PDF):For detailed PDF specifications, please scan WeChat and contact us. You can also get free samples and technical support.!
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| Model | VCC starting voltage | VCC shutdown voltage | Input voltage range | Starting current | Switching frequency | Output voltage accuracy | Built-in power tube | Features | Encapsulation |
| CXDC65167 | 6.5V | 3.5V | 20-60V | Built-in quick start | 10-100K, peripheral can be set | 3% | Yes | 48v battery power supply system step-down switch power chip | ESOP8 |
| CXAC85204 | 16V | 9V | 20-150V | 3uA | Tiktok | 1.5% | Yes | Non-isolated system constant voltage stable output current | SOP7 |
| CXAC85207 | 9.5V | 7.8V | 10-25v | 80uA | 0-300K, peripheral adjustable | 1.50% | None | Programmable power supply chip | SOP16 |
| CXLB73135 | 9.5V | 7.8V | 10-25v | 80uA | 0-300K, peripheral adjustable | 1.50% | None | Programmable power supply chip | SSOP24 |
| CXDC65168 | 6.5V | 3.5V | 10-600V | 200uA | 0-300K, peripheral can be set | 1.5% | None | Synchronous rectification, highEfficiency, can support constant current and constant voltage charging of battery | SOP16 |
| CXSU63303 | - | - | 7-150V | External Auxiliary power supply | 70k | 1.5% | None | Boost and Buck control chip, supporting high voltage and large current protection scheme | QFN32 |
| CXSU63304 | - | - | 13-90V | External Auxiliary power supply | 100K | 1.5% | None | Step-down digital power chip supporting PD3.0 protocol | QFN64 |
| CXSU63305 | 3.65V | 3.6V | 4-600V | 50uA | 0-300K, peripheral can be set | 1.5% | None | Boost synchronous rectification scheme, supporting high voltage and large current scheme | SOP16 |
| CXSD62669 | 16V | 9V | 20-90V | 3uA | Tiktok | 1.5% | Yes | Non-isolated system constant voltage stable output current | SOP7 |
| CXSD62670 | 16V | 9V | 20-600V | 3uA | Tiktok | 1.5% | Yes | Non-isolated system constant voltage stable output current | SOP7 |
| CXSD62671 | - | - | 10-115V | Built-in quick start | 140kHz | 3% | None | Short circuit hiccup, flexible and adjustable output voltage | ESOP8 |
| CXSD62672 | - | - | 10-115V | Built-in quick start | 120kHz | 3% | None | Short circuit lock, flexible and adjustable output voltage | ESOP8 |
| CXSD62673 | - | - | 10-100V | Built-in quick start | 120kHz | 3% | Yes | Zero power consumption enabled, flexible and adjustable output voltage | ESOP8 |
| CXSD62674 | - | - | 10-120V | Built-in quick start | 120kHz | 3% | Yes | Zero power consumption enabled, flexible and adjustable output voltage | ESOP8 |
| CXSD62675 | - | - | 10-120V | Built-in quick start | 120kHz | 3% | Yes | Short circuit hiccup, flexible and adjustable output voltage | ESOP8 |
| CXSD62676 | - | - | 10-120V | Built-in quick start | 120kHz | 3% | None | Short circuit hiccup, flexible and adjustable output voltage | ESOP8 |
| CXSD62677 | - | - | 10-120V | Built-in quick start | 70kHz | 3% | None | Short circuit lock, flexible and adjustable output voltage | ESOP8 |
| CXSD62678 | 4.6V | 3.8V | 4-600V | 50uA | 0-300K, peripheral can be set | 1.5% | None | Step-down synchronous rectification scheme, supporting high voltage and large current scheme | SOP16 |
| CXSD62679 | 16.5V | 8V | 10-600V | 200uA | 0-300K, peripheral can be set | 1.5% | None | Synchronous rectification, highEfficiency, can support constant current and constant voltage charging of battery | SOP16 |
| CXSD62680 | 8.5V | 7.5V | 10-600V | 200uA | 0-300K, peripheral can be set | 1.5% | None | Synchronous rectification, highEfficiency, can support constant current and constant voltage charging of battery | SOP16 |
| CXSD62681 | 9.5V | 7.8V | 11-250V | 200uA | 0-300K, peripheral can be set | 1.5% | None | Synchronous rectification, highEfficiency, short circuit lock, built-in temperature protection, etc. | SSOP16 |
| CXSD62682 | 9.5V | 7.8V | 11-100V | 200uA | 0-300K, peripheral can be set | 1.5% | Yes | Synchronous rectification, highEfficiency, short circuit lock, built-in temperature protection, etc. | QFN32 |
| CXSD62683 | 9.5V | 7.8V | 11-30V | 200uA | 0-300K, peripheral can be set | 1.5% | Yes | Synchronous rectification, highEfficiency, short circuit lock, built-in temperature protection, etc. | QFN32 |
| CXSD62684 | - | - | - | External Auxiliary power supply | Maximum operating frequency 100kHz | - | None | Digital algorithm current mode synchronous buck control chip | SSOP24 |
| CXSD62685 | 9.5V | 7.8V | 10-25v | 80uA | 0-300K, peripheral adjustable | 1.50% | None | Synchronous rectifier step-down power supply control chip | SSOP16 |
