Analog Devices Inc. LTC1429CS8-4

Overview

LTC1429CS8-4 from Analog Devices (formerly Linear Technology) is a fixed-output, clock-synchronized switched-capacitor voltage inverter that generates a regulated –4V output from a 5V supply. It delivers up to 10mA output current with ±5% regulation, 10mV typical output ripple, and operates with an external 700kHz synchronization clock. It serves as a compact negative bias supply in single-supply analog signal chains and low-noise sensor interfaces.

For engineers reviewing the LTC1429CS8-4 datasheet, LTC1429CS8-4 pinout, LTC1429CS8-4 application, or LTC1429CS8-4 equivalent, key selection criteria include its SO-8 package, fixed –4V output, external clock dependency, REG flag for power-valid indication, and shutdown capability reducing supply current to 0.2µA.

Technical Context

The LTC1429CS8-4 implements a doubler-mode charge pump topology with internal resistor string configured for –4V output, requiring only one 0.1µF flying capacitor between C1+ and C1–. Regulation is achieved via a 1.24V internal reference and comparator-based duty-cycle control of the charge transfer cycle.

Its open-drain REG output asserts low when VOUT is within ±5% of –4V (i.e., –3.80V to –4.20V), and the SYNC/SD pin accepts TTL/CMOS clock inputs from 60kHz to 2MHz - enabling noise-sensitive system synchronization. Shutdown is entered by holding SYNC/SD high or low, dropping quiescent current to 0.2µA.

Key Specifications

Pinout & Package

Package: 8-pin SOIC (SO-8), 150°C maximum junction temperature, 110°C/W thermal resistance.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar regulated negative voltage inverter applications.

Compared with LTC1429CS-4, LTC1429CS8-4 offers smaller footprint and simpler BOM but sacrifices adjustability; compared with LTC1550IS8-4, it trades lower ripple and internal oscillator for lower quiescent current and external clock control - making it optimal for noise-managed, clock-synchronized, space-constrained designs.

Availability

LTC1429CS8-4 is available at Aetrix Electronics and suitable for industrial sensor conditioning, portable medical instrumentation, automotive audio biasing, and test equipment requiring stable component supply with guaranteed long-term sourcing.

Supply support for LTC1429CS8-4 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

Analog Devices, Inc. (ADI) is a global leader in high-performance analog, mixed-signal, and digital signal processing technologies, serving industrial, automotive, communications, and healthcare markets.

The LTC1429 product line was developed by Linear Technology (acquired by ADI in 2017) specifically for low-noise, clock-synchronized, switched-capacitor negative voltage generation in space- and power-constrained applications.

FAQ

What is the exact output voltage tolerance of the LTC1429CS8-4?

The LTC1429CS8-4 guarantees a fixed –4V output with ±5% regulation accuracy, meaning the actual output remains between –3.80V and –4.20V across 0°C to 70°C temperature range and 0–10mA load. This is confirmed in the Electrical Characteristics table under "VOUT" parameter with MIN/TYP/MAX values of –3.80V/–4.00V/–4.20V.

Does the LTC1429CS8-4 require an external clock to operate?

Yes, the LTC1429CS8-4 requires an external TTL/CMOS-compatible square-wave clock applied to the SYNC/SD pin for normal operation. The minimum frequency is 60kHz at VCC ≤ 5V; operation below this threshold may cause intermittent shutdown. No internal oscillator is present - unlike the LTC1550 series.

Can the LTC1429CS8-4 be used with a 3.3V input supply?

No - the LTC1429CS8-4 is optimized for 5V input and is not rated for reliable –4V regulation from 3.3V. Its absolute minimum VCC is 3V, but the datasheet specifies it is "optimized for applications which require a fixed –4V output from a 5V supply." At 3.3V, output regulation degrades significantly and falls outside ±5% spec.

What is the function of the COMP pin on the LTC1429CS8-4?

On the LTC1429CS8-4, the COMP pin serves as the compensation node for the internal regulation loop. Connecting a 1000pF capacitor from COMP to GND reduces output voltage ripple and improves loop stability - especially critical when routing sensitive analog traces near the SYNC/SD clock line.

How does the REG pin indicate regulation status on the LTC1429CS8-4?

The REG pin on the LTC1429CS8-4 is an open-drain output that pulls low (≤0.8V at 1mA sink) when the –4V output is within ±5% of nominal (i.e., –3.80V to –4.20V). It remains high-impedance otherwise and requires an external pull-up resistor to a logic voltage (up to 12V) to assert a valid logic-high state.