Is there a pin-compatible replacement for CJ7550S?

No fully pin-compatible replacement is confirmed. CJA1117B-5.0 has the same SOT-89-3L package but is not electrically equivalent, with a much lower input voltage limit and higher dropout voltage. It requires careful engineering review.

What risks should I check before replacing CJ7550S?

Key risks are: 1) Package mismatch requiring a new PCB layout. 2) Lower maximum input voltage, which can damage the part if your system exceeds it. 3) Higher quiescent and dropout current, which will reduce efficiency and battery life.

CJ7550S Alternatives, Datasheet & Cross Reference | Jiangsu Changjing Electronics Technology Co., Ltd.

The CJ7550S is a 5V, 300mA low-dropout (LDO) regulator in a SOT-89-3L package, notable for its very low 2µA quiescent current and wide 36V input range, making it ideal for power-sensitive applications.

AI replacement insight

Package riskhigh

Most alternatives are in different packages, requiring a PCB redesign.

Electrical riskhigh

Candidates have lower max input voltage and/or much higher quiescent current and dropout voltage.

Sourcing riskmedium

The target's specific combination of features may be difficult to source from other vendors.

Can it be replaced directly?

No direct pin-to-pin replacement has been identified. The CJA1117B-5.0 shares the SOT-89-3L package but has critical electrical limitations, making it a high-risk downgrade.

Best replacement path

Finding a direct drop-in replacement is difficult. The CJA1117B-5.0 matches the package but has a much lower 15V input limit. For better electrical performance, a redesign for a part like the LDL1117S50R may be needed, if its 18V limit is acceptable.

Main risk

The main risks are package mismatches requiring board redesign, and electrical downgrades like lower maximum input voltage and much higher quiescent current.

Recommended alternatives

A functional alternative with good LDO performance but requires a board redesign due to a different package.

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Alternative comparison matrix

Feature / factor	CJ7550S	LDL1117S50R	CJA1117B-5.0	Compatibility / risk
Package	SOT-89-3L	SOT223	SOT-89-3L	SOT223 / SOT-89-3L — Different package requires board redesign.; CJA1117B-5.0: Package matches, enabling potential drop-in.
Voltage	36V	18V	15V	18V / 15V — Max input voltage is significantly lower.; CJA1117B-5.0: Max input voltage is significantly lower.
Current	0.3A	1.2A	1.0A	1.2A / 1.0A — Higher output current capability.; CJA1117B-5.0: Higher output current capability.
Dropout Voltage	200mV @ 100mA	350mV @ 1.2A	1.15V	350mV @ 1.2A / 1.15V — Good LDO performance, though slightly higher dropout.; CJA1117B-5.0: Dropout voltage is much higher, not a true LDO.
Temperature	-40°C to 85°C	-40°C to 125°C	0°C to 125°C	-40°C to 125°C — Wider operating temperature range.; CJA1117B-5.0: Operating temperature range does not cover low end.

Application & sourcing insights

Questions & answers

The best alternative depends on your priority. For matching the package, CJA1117B-5.0 is an option if the lower 15V max input is acceptable. For better LDO performance, a part like LDL1117S50R is an option but requires a board redesign.