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LF353: Significant output high-voltage difference between two LF353 device lots at ±5 V supply

Song Xue — Fri, 11 Sep 2026 09:11:33 GMT

Part Number: LF353

Hello,

We have observed a significant difference in the high-level output voltage between two lots of TI LF353 devices in the same application, and would like to confirm whether this behavior could be expected due to different device revisions or manufacturing lots.

The LF353 is powered from +5 V / -5 V and is used as an open-loop comparator with hysteresis. The output also drives an optocoupler input through a diode and series resistor.

Under the same static test condition (no input signal), we measured the following output voltages:

Board	PCB Version	LF353 Top Marking	Output Voltage
Board 1	CS-V1.0	LF353 TI 46M A434	3.37 V
Board 2	CS-V1.1	LF353 TI 46M A434	3.35 V
Board 3	CS-V1.1	LF353 TI 53K CL42	4.49 V
Board 4	ZS/JX-V1.1	LF353 TI 53K CL42	4.747 V
Board 4, after replacing LF353	ZS/JX-V1.1	LF353 TI 46M A434	3.59 V

The most important observation is from Board 4. We replaced only the LF353 device on the same PCB, without changing the surrounding circuit. The output voltage changed from approximately 4.747 V with the "53K CL42" device to 3.59 V with the "46M A434" device.

Therefore, the difference appears to follow the LF353 device rather than the PCB.

Both devices are marked as TI LF353. Since the LF353 is not a rail-to-rail output amplifier, the approximately 3.3–3.6 V output level at a +5 V supply appears reasonable to us. However, the approximately 4.5–4.75 V output level of the "53K CL42" devices is much closer to the positive supply rail.

Could TI please help clarify the following?

Are "46M A434" and "53K CL42" valid TI LF353 top markings / lot or traceability codes?
Could these devices correspond to different silicon revisions or manufacturing processes?
Is an output high level of approximately 4.5–4.75 V with a +5 V supply expected for any TI LF353 revision under load?
Is the observed difference between approximately 3.4 V and 4.7 V within the expected device variation?
Are there any additional measurements we should perform to identify the cause of this difference?

We can provide the schematic, photographs of the device markings, supply voltages, output load current, and additional measurements if required.

Thank you.

RE: LF353: Significant output high-voltage difference between two LF353 device lots at ±5 V supply

Vivian Gao — Fri, 11 Sep 2026 09:53:04 GMT

感谢您关注TI产品。我们正在核实您的问题，请耐心等待我们的回复。

RE: LOG114: The recommended circuit in the datasheet's typical application, which generates ±5V power from a 3.3V power supply, can't support the normal operation of LOG114

Vivian Gao — Fri, 11 Sep 2026 06:40:54 GMT

Thank you for your attention to TI products. We are verifying your issue, please wait for our reply.

LOG114: The recommended circuit in the datasheet's typical application, which generates ±5V power from a 3.3V power supply, can't support the normal operation of LOG114

Xu Ricardo — Wed, 02 Sep 2026 05:20:14 GMT

Part Number: LOG114

I used the recommended circuit to power the LOG114 with ±5V, but it could not support the normal operation of the LOG114. I then directly used an external power supply to provide 5V to this buck-boost circuit. Using a current probe with an oscilloscope to measure, I found that the LOG114 requires a current of 74mA. I checked the TPS60400 datasheet and found that its maximum output current is 60mA, so the preliminary judgment is that the cause is insufficient output current. However, the operating current of the LOG114 is 10mA, which differs significantly from the actual measurement. What could be the reason for this?

BUF802RGTEVM: BUF802芯片输出不平

kang chen — Tue, 08 Sep 2026 12:23:05 GMT

Part Number: BUF802RGTEVM

BUF802之前信号如下：

BUF802输出信号如下：

使用的复合环路模式，原理图如下所示

输出波形不平（下凹）的问题出在哪？

RE: BUF802RGTEVM: BUF802芯片输出不平

Daniel — Fri, 11 Sep 2026 06:30:02 GMT

您好

已经收到了您的案例，调查需要些时间，感谢您的耐心等待

RE: OPA549-HIREL: 封装问题

Vivian Gao — Thu, 10 Sep 2026 01:56:14 GMT

不建议，因为无法手动成型无法确认会不会让芯片内部连接受损。

OPA549-HIREL: 封装问题

Zhou Zhou Shuangwu — Mon, 07 Sep 2026 08:17:09 GMT

Part Number: OPA549-HIREL

OPA549MKVC的引脚能否掰成OPA549T那样的就是把前面这个掰成后面这样焊上去

TIDA-060029: 参考设计2.3.2.1章节中传递函数的计算是否有误

Alex Liu — Fri, 28 Aug 2026 02:06:30 GMT

Part Number: TIDA-060029

这里列出的传递函数和其极点与零点似乎对不上，

如果函数（4）是正确的，那么极点和零点应该是：

零点wz=1/RgCx

极点wp=1/（Rf+Rg）Cx

我自己的计算的传递函数为，

1/β=1+（Rf+Rg）SCx/1＋SRgCx

这个结果和图 2-8 中展示的波特图也是可以对上的，

因此我怀疑2.3.2.1的传递函数，分子和分母写反了。

RE: TIDA-060029: 参考设计2.3.2.1章节中传递函数的计算是否有误

Alex Liu — Fri, 04 Sep 2026 01:13:47 GMT

谢谢确认，那你们什么时候更新一下这篇参考设计吧

RE: TIDA-060029: 参考设计2.3.2.1章节中传递函数的计算是否有误

Eirwen — Fri, 04 Sep 2026 00:30:30 GMT

您的计算应该是正确的。

RE: TINA-TI_SIMP_CHINESE: INA826 仿真相位裕度不够?

chen emmy — Mon, 31 Aug 2026 03:22:23 GMT

谢谢 Vivian的解答。第一张张图片是参考TI网站上的参考设计，应该没有问题，第二张图是参考设计里的截图，和我仿真的结果一样。第二张图里的测试条件和datasheet里标注的测试条件的确不相同。数据手册里典型值G=100时的-3dB带宽60kHZ,和仿真结果差不多。想看看下图电路中U1的相位裕度，请问该怎么仿真查看呢？附上仿真电路。谢谢e2echina.ti.com/.../_296E65882B003E652759F8764D4FD588A65E_.TSC

TINA-TI_SIMP_CHINESE: INA826 仿真相位裕度不够?

chen emmy — Wed, 26 Aug 2026 05:55:34 GMT

Part Number: TINA-TI_SIMP_CHINESE

大家好！用INA826的参考设计仿真相位裕度时，出现图片中的-271.97°，按照相位裕度的定义，PM=180°+0dB处频率所对应的相位，那PM=180°+(-271.97°）=-91.97°，这说明相位裕度不够。但这是参考电路，应该不会有问题，那到底哪里有问题？谢谢。

仿真出来的增益图和参考设计中的截图（如下图）相同，说明仿真的原理图没有问题。为什么相位裕度不够？要怎么解释比较合理？

RE: TINA-TI_SIMP_CHINESE: INA826 仿真相位裕度不够?

Vivian Gao — Mon, 31 Aug 2026 01:08:28 GMT

这不是参考设计出问题，也不是仿真出错，而是分析方法用错了对象：把"闭环增益-相位响应"套用了只适用于"开环环路增益"的相位裕度公式。
对于像INA826这种反馈环完全集成在芯片内部、无法从外部访问的仪表放大器，TI已经在IC设计阶段保证了内部环路的稳定性，用户无法也不需要在TINA-TI里重新验证"相位裕度"。
您真正应该关注、且数据手册给出的指标是闭环带宽（datasheet: G=1时1MHz，G=100时60kHz），而不是自行推算相位裕度。您截图里RG=499Ω对应G=100，仿真中0dB穿越点在~2.29MHz，比数据手册典型60kHz带宽高出不少的原因，可能是TINA-TI宏模型/测试条件（负载、AC小信号设置）与数据手册标准测试条件不同，这个可以单独核对，但与"相位裕度为负"无关，那个数字本身就是无意义的。

LM2901: PIN 脚颜色不一样

sharry-yao yao — Fri, 28 Aug 2026 02:57:48 GMT

Part Number: LM2901

左图 D/C 2435 PIN 银白色；下图右 D/C 2606+5，整盘来料，PIN 暗色

RE: LM2901: PIN 脚颜色不一样

Eirwen — Fri, 28 Aug 2026 04:36:58 GMT

请按照以下链接联系客户支持中心，会有客服为您提供帮助：
ticsc.service-now.com/csm

RE: LM2901: PIN 脚颜色不一样

FRANK1 — Fri, 28 Aug 2026 03:00:44 GMT

感谢您对TI产品的关注！关于你的咨询，我们正在确认您的问题，感谢您的耐心等待。

RE: TIDA-060029: 参考设计2.3.2.1章节中传递函数的计算是否有误

Eirwen — Fri, 28 Aug 2026 02:11:00 GMT

已经收到了您的案例，调查需要些时间，感谢您的耐心等待。

INA381-Q1: INA381电路开发

zuotao xu — Fri, 21 Aug 2026 06:35:42 GMT

Part Number: INA381-Q1

如果我的电源地只能放在IN+（电池正极端），那么这个电路应该如何应用，还是说这颗芯片只能应用于GND在电池负极的情况。或者有没有其他的类似芯片可以满足要求。

RE: INA381-Q1: INA381电路开发

Eirwen — Thu, 27 Aug 2026 02:41:59 GMT

负载load那里，IN+接地，IN-是多少？您看下可能无法满足共模输入电压。

RE: TINA-TI_SIMP_CHINESE: INA826 仿真相位裕度不够?

Eirwen — Wed, 26 Aug 2026 09:14:48 GMT

已经收到了您的案例，调查需要些时间，感谢您的耐心等待。

RE: LM2901: 请提供PCN

Lydia — Tue, 25 Aug 2026 07:43:31 GMT

您好，

TI 论坛旨在解决客户在使用TI产品过程中遇到的技术问题。关于PCN问题，建议您请按照以下方式联系客户支持部门，会有客服为您提供帮助。
打开链接www.ti.com.cn/.../customer-support.html

LM2901: 请提供PCN

sharry-yao yao — Tue, 25 Aug 2026 07:39:50 GMT

Part Number: LM2901

D/C 2435 ， PIN 银白色； D/C 2606+5，PIN 暗色,颜色不一样，中间颜色变化请提供PCN

RE: INA381-Q1: INA381电路开发

Eirwen — Fri, 21 Aug 2026 06:43:18 GMT

已经收到了您的案例，调查需要些时间，感谢您的耐心等待。

PGA280: PGA280 断线检测问题

guangyi chen — Sat, 15 Aug 2026 04:29:29 GMT

Part Number: PGA280

PGA280 如何进行双线和单线断线检查的，具体步骤有哪些？在每一步中具体关闭或打开A1/2 B1 /2 C1/2内部的MUX的哪些开关？