Analog Devices Inc./Maxim Integrated DS1780E

Overview

DS1780E from Maxim Integrated (now Analog Devices) is a highly integrated CPU peripheral monitor IC for PC and embedded microprocessor systems. It performs real-time monitoring of ambient temperature (±0.5°C LSB, 9-bit two's complement), six power supply voltages (+12V, +5V, +3.3V, +2.5V, +VCCP1, +2.5VS/+VCCP2), and two fan tachometer inputs - all with internal 8-bit ΔΣ ADC and programmable fan speed control via an 8-bit DAC output (0–1.25V). It supports chassis intrusion detection with latched state retention even during power-off.

For engineers reviewing the DS1780E datasheet, DS1780E pinout, DS1780E application, or DS1780E equivalent, this page delivers verified technical context, exact pin functions, confirmed voltage monitoring resolution (e.g., 13.0 mV/LSB on +2.5VIN), true interrupt behavior (programmable SMI on voltage/temp/fan/chassis events), and validated alternatives for system instrumentation design in desktop, server, and industrial control platforms.

Technical Context

The DS1780E integrates a 9-bit temperature sensor, six analog voltage inputs with internal scaling and 8-bit ΔΣ conversion, dual fan tachometer counters with selectable divisors (1/2/4/8), and an 8-bit DAC for closed-loop fan control. Its 2-wire serial interface uses a 2-bit address (A0/A1) and supports slave address reprogramming via Serial Address Register (0x48h).

It implements three programmable temperature interrupt modes (one-time, default, comparator), per-channel voltage high/low limit comparison, fan count-based failure detection (e.g., 70% RPM = 219 counts @ ÷2 mode), and hardware-level chassis intrusion latching with open-drain CHS reset capability - all managed through dedicated configuration, status, and mask registers mapped to I²C-accessible addresses (0x40h–0x49h, 0x20h–0x3Dh).

Key Specifications

Pinout & Package

DS1780E is housed in a 24-pin 173-mil TSSOP package (JEDEC MO-153), optimized for low-profile motherboard placement and thermal performance. Pin spacing is 0.65 mm; body dimensions are 7.8 mm × 4.4 mm × 1.2 mm.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar CPU peripheral monitoring applications.

Compared with DS1780E, LM95235CIMM/NOPB offers higher temperature resolution but no system-level monitoring; ADM1027ARUZ provides SMBus compatibility and VRM support but lacks the DS1780E's integrated DAC and intrusion latching - making DS1780E uniquely suited for self-contained, low-BOM-cost PC instrumentation.

Availability

DS1780E is available at Aetrix Electronics and suitable for desktop motherboard production, server board qualification, and industrial embedded controller design requiring stable component supply and long-term lifecycle assurance.

Supply support for DS1780E includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Maxim Integrated (acquired by Analog Devices in 2021) is a leader in precision analog, mixed-signal, and power management ICs for computing, industrial, and communications infrastructure.

The DS1780E belongs to Maxim's CPU Peripheral Monitor product line - designed specifically to consolidate power, thermal, and mechanical monitoring functions into a single chip for x86 and embedded microprocessor platforms.

FAQ

What is the temperature measurement accuracy and format used by the DS1780E?

The DS1780E measures ambient temperature with 0.5°C least significant bit (LSB) resolution and outputs data in 9-bit two's complement format. The value is stored at internal address 0x27 and represents degrees Celsius directly - for example, 0x19 = +25°C, 0xFF = −1°C. No external calibration is required, and the sensor is factory-trimmed for ±1°C accuracy over 0°C to +70°C.

How does the DS1780E support fan speed control, and what is the DAC output specification?

The DS1780E includes an 8-bit DAC that outputs a 0–1.25V analog signal at the VOUT/NTIN pin (Pin 11), intended for direct interfacing with fan driver circuits. This eliminates the need for external PWM generation or filtering components. The DAC value is written to internal register 0x19 and updates immediately; full-scale output corresponds to 0xFF (255 decimal).

Can the DS1780E monitor negative supply voltages like −12V, and if so, how?

Yes, the DS1780E can monitor −12V using the +2.5VS/+VCCP2 input (Pin 14) with an external resistor ladder (e.g., R1 = 4 kΩ, R2 = 23.2 kΩ) referenced to +5V. This scales −12V to 0–3.6V at the pin, matching the ADC's input range. The resulting conversion uses 14.1 mV/LSB resolution, and the raw count maps to supply voltage via Table 6 in the datasheet.

What are the interrupt capabilities of the DS1780E, and how are they configured?

The DS1780E supports four interrupt sources - temperature, six voltage channels, two fan speeds, and chassis intrusion - each individually maskable in two interrupt mask registers (0x43h and 0x44h). The active-low INT pin (Pin 10) is enabled via Bit 1 of the Configuration Register (0x40h). Interrupt status is latched in two status registers (0x41h/0x42h) and cleared upon read or via the INT_Clear bit (Bit 3 of 0x40h).

Does the DS1780E retain chassis intrusion state when powered off, and how is it cleared?

Yes, the DS1780E retains chassis intrusion state even when VDD is removed, because the CHS pin (Pin 7) is designed to accept and latch an active-high signal from an external mechanical/optical switch. To clear the latched state, the DS1780E drives CHS low for ≥20 ms when Bit 6 of the Configuration Register (0x40h) is set - a hardware action independent of VDD presence.