MAX138EQH - 3.5-Digit LCD ADC with Reference | Analog Devices
料号： MAX138EQH ✓ 量产中MAX138EQH 概述
An analog-to-digital converter, or ADC, converts an analog input voltage into a digital code for measurement, display, control, or data processing. The MAX138EQH belongs to the dual-slope ADC family and resolves approximately 3.5 decimal digits. A 3.5-digit display commonly represents a full-scale value from 0000 through 1999, allowing the converter to resolve one count in a 2000-count measurement range. This resolution is well suited to digital panel meters, laboratory instruments, and process-monitoring equipment where direct numerical display is more useful than a high-resolution waveform representation.
Integrated features reduce the number of surrounding components in a meter design. The on-chip reference establishes the conversion reference, while the charge-pump circuit supports the specified single-supply operating range. Direct LED drivers allow the converter to drive display elements without a separate display-driver IC. According to the Analog Devices product documentation, the MAX138 family also accepts bipolar input signals, allowing a frontend to measure positive or negative quantities relative to a defined common reference.
The dual-slope conversion architecture integrates the input over a fixed measurement interval and compares the result against a reference ramp. This approach is well matched to slowly changing measurements such as temperature, pressure, level, weight, and laboratory process variables. Its practical benefits include effective rejection of periodic interference, straightforward integration into digital meters, and a direct path to LED-segment display outputs. These characteristics are more valuable than maximum conversion speed for this class of instrumentation.
Typical uses include bench-top digital multimeters, temperature controllers, panel meters, laboratory displays, industrial process indicators, and compact weighing or dispensing equipment. The MAX138EQH is particularly appropriate when a readable three-and-a-half-digit result, bipolar input capability, and direct display excitation are desired in one IC. Designers should still verify front-panel drive requirements, reference accuracy, input filtering, and timing behavior against the manufacturer datasheet before laying out the PCB.
A key design consideration is that the converter, reference, display outputs, and power supply share a compact analog and mixed-signal layout. Keep the input and reference paths compact, maintain stable supply decoupling near the device, and route display-drive currents away from sensitive measurement nodes. Validate the complete meter accuracy with the intended transducers, wiring, grounding, and display rather than relying only on nominal converter resolution.
This product page combines the Analog Devices MAX138 family specifications with practical guidance for LCD meter design, drop-in family alternatives, package-aware comparison, and application-oriented selection. It highlights where the integrated reference, charge pump, bipolar-input capability, and LED drivers simplify a design while distinguishing it from unrelated converter families that use different packages, interfaces, or measurement architectures.
直接替换替代料： MAX138EQH ——相同封装，引脚兼容。需要 PCB 改动的不同封装料号已排除。
本系列中的变体
可与以下型号直接替换的同系列型号： MAX138EQH （相同外形与封装尺寸） ——差异在于 Charge Pump, Package.
MAX138EQH+D
✅ 直接替换📋 参考替代料（不在目录中）
MAX138CQH+D
✅ 直接替换📋 参考替代料（不在目录中）
MAX138CQH+TD
✅ 直接替换📋 参考替代料（不在目录中）
MAX138CMH+C10166
✅ 直接替换📋 参考替代料（不在目录中）
MAX138EPL+
✅ 直接替换 ⚠️ 规格未核验联系询价
查看数据手册 →MAX138EQH 最大额定值与电气特性
| ADC Type | Dual-slope, 3.5-digit ADC |
| Number of Channels | 1 channel |
| 分辨率 | 3.5 decimal digits |
| Supply Voltage Range | +2.5 V to +7 V |
| Input Signal Capability | Bipolar input |
| Internal Reference | Integrated |
| Charge Pump | Integrated |
| Display Driver | Direct LED drivers |
| Data Interface | Serial |
| 封装 | 44-pin PLCC, J-lead, 16.59 mm x 16.59 mm |
| 工作温度 | -40 °C to +85 °C |
| Packaging | Tube |
| Production Status | Production |
MAX138EQH 44-pin plcc, j-lead, 16.59 mm x 16.59 mm 引脚配置指南
MAX138EQH（44-pin plcc, j-lead, 16.59 mm x 16.59 mm 封装）的引脚配置。 该模拟元件具有输入、输出和电源引脚。请参阅制造商数据手册以了解失调调零、补偿和使能引脚配置。适用于信号调理和放大器电路。
暂无详细引脚数据： MAX138EQH.
请参阅 数据手册 以查看完整引脚配置。
典型应用
MAX138EQH 适用于 6 应用s: Digital Panel Meters, Temperature Measurement Instruments, Laboratory Digital Instruments, Industrial Process Indicators, Bench-Top Digital Multimeter, Load and Balance Displays.
Digital Panel Meters
The MAX138EQH fits digital panel meters because its 3.5-digit dual-slope ADC, internal reference, and direct LED drivers combine measurement and display functions in one IC. The single +2.5 V to +7 V supply simplifies low-voltage instrument design, while bipolar-input capability supports meters that display both positive and negative readings. In a panel-meter implementation, the sensor signal is conditioned into the permitted input range, and the converter drives the segmented display directly. The architecture is most appropriate for slow-changing measurements where readable resolution is more important than rapid conversion throughput.
推荐
Temperature Measurement Instruments
The MAX138EQH is suitable for thermocouple, RTD, or resistance-based temperature instruments when the front end converts the sensed temperature into a bipolar voltage. Its 3.5-digit resolution provides a practical numerical display range, and the integrated reference, charge pump, and LED drivers reduce the number of separate support components. The dual-slope ADC is particularly suitable for thermal signals that change relatively slowly. Front-end amplifier gain, input protection, and sensor wiring must be designed so the complete instrument meets its intended accuracy rather than relying on converter resolution alone.
推荐
Laboratory Digital Instruments
A laboratory display instrument can use the MAX138EQH when a direct, readable three-and-a-half-digit measurement is preferable to a high-speed converter output. The device accepts bipolar inputs and includes an internal reference, which simplifies the central signal chain around slowly varying laboratory quantities. Its +2.5 V to +7 V operating range allows use with common low-voltage regulated supplies. Designers should add suitable input attenuation, filtering, calibration, and protection while verifying reference accuracy, noise performance, and display-drive limits in the manufacturer datasheet.
推荐
Industrial Process Indicators
The MAX138EQH supports industrial process indicators for pressure, flow, level, or other slowly varying process variables. Its dual-slope conversion architecture is appropriate when the process signal changes gradually, and the integrated reference and display drivers help create a compact front panel. Bipolar input capability accommodates positive and negative readings around the process zero point. The measurement conditioner should include electrical isolation or protection where required, while the PCB should keep high-current display and actuator wiring away from sensitive analog nodes.
推荐
Bench-Top Digital Multimeter
The MAX138EQH can serve as the display converter in a bench-top digital multimeter designed around a three-and-a-half-digit numerical indication. It combines a one-channel dual-slope ADC with an internal reference, charge pump, and LED drivers, while accepting bipolar inputs for resistance, voltage, or temperature-derived measurements. The 44-pin PLCC package is relatively large compared with modern surface-mount ADC packages, but it remains practical for leaded legacy-style and industrial instrument designs. Input switching, protection, calibration, and safety barriers remain functions of the complete meter rather than the converter alone.
推荐
Load and Balance Displays
The MAX138EQH is applicable to compact load-cell indicators, weighing systems, and balance displays that need a straightforward numeric result rather than a rapid conversion stream. The 3.5-digit resolution and integrated LED drivers suit a basic commercial display, while the internal reference helps simplify the converter subsystem. Mechanical shock, sensor lead noise, common-mode voltage, and input grounding often determine real weighing accuracy. Use the device within its electrical limits, retain the dual-slope advantage for slowly varying forces, and validate calibration across the full sensor and load range.
推荐
推荐产品汇总
工程参考数据： MAX138EQH ——对比、设计指导和合规信息。
选型指南
与替代料对比
| 参数 | 本产品 | MAX138EQH+D | MAX138CQH+D | MAX138CQH+TD | MAX138CMH+C10166 | MAX138EPL+ |
|---|---|---|---|---|---|---|
| Package | 44-pin PLCC, J-lead | 44-pin PLCC | 44-pin PLCC | 44-pin PLCC | 44-pin PLCC | 44-pin PLCC |
| Brand | Analog Devices | Analog Devices | Analog Devices | Analog Devices | Analog Devices | Analog Devices |
| ADC Architecture | Dual-slope ADC | Dual-slope ADC | Dual-slope ADC | Dual-slope ADC | Dual-slope ADC | Dual-slope ADC |
| Resolution | 3.5 decimal digits | 3.5 decimal digits | 3.5 decimal digits | 3.5 decimal digits | 3.5 decimal digits | 3.5 decimal digits |
| Number of Channels | 1 channel | 1 channel | 1 channel | 1 channel | 1 channel | 1 channel |
| Supply Voltage Range | +2.5 V to +7 V | +2.5 V to +7 V | +2.5 V to +7 V | +2.5 V to +7 V | +2.5 V to +7 V | +2.5 V to +7 V |
| Input Capability | Bipolar input | Bipolar input | Bipolar input | Bipolar input | Bipolar input | Bipolar input |
| Integrated Features | Reference, charge pump, direct LED drivers | Reference, charge pump, direct LED drivers | Reference, charge pump, direct LED drivers | Reference, charge pump, direct LED drivers | Reference, charge pump, direct LED drivers | Reference, charge pump, direct LED drivers |
| Interface | Serial | Serial | Serial | Serial | Serial | Serial |
关键差异点
- Integrated display-meter signal chain （对比 MAX138EQH+D)
- Single-supply operation with internal charge pump （对比 MAX138CQH+D)
- Direct LED output integration （对比 MAX138CMH+C10166)
- Bipolar measurement capability （对比 MAX138CQH+TD)
设计说明
Place the input-conditioning network, reference bypass, and supply-decoupling components close to the corresponding MAX138EQH pins. Keep the analog input traces short and separate them from display-drive and external switching currents. A compact, ground-referenced analog region reduces susceptibility to errors that can appear as unstable meter readings even when the converter itself is operating correctly.
Use a low-noise, low-drift reference arrangement and route the analog node away from the direct LED-drive outputs. Display multiplexing and external relays can inject transient current into sensitive measurement paths. If the input source has high source impedance, include suitable filtering and account for settling time in the dual-slope measurement cycle. Confirm all input and reference limits in the manufacturer datasheet before setting the gain network.
Do not assume that a related MAX138 suffix is automatically interchangeable. Verify the ordering table, temperature grade, package, pin assignment, and lifecycle configuration for MAX138EQH+D, MAX138CQH+D, or other family members before replacing an installed device. Also avoid driving display outputs beyond their specified limits and provide suitable protection for external sensor wiring, where the measurement system can experience transients or ground-potential differences.
Use a continuous ground plane beneath and around the device, but partition high-current display and switching paths from the measurement-return path. Decouple the +2.5 V to +7 V supply close to the IC and control the amount of copper attached to sensitive signal nodes if leakage or temperature gradients affect accuracy. Review the manufacturer's recommended PCB layout and test setup before releasing a multi-channel or high-precision meter design.
合规信息
The MAX138 family is listed as production by Analog Devices, but explicit RoHS, REACH, lead-free, halogen-free, and conflict-minerals declarations are not present in the available product information. AEC-Q100 is not applicable to this general-purpose meter ADC.
