Analog Devices Inc. LTC1429CS

Overview

LTC1429CS from Analog Devices (formerly Linear Technology) is a clock-synchronized, switched-capacitor regulated negative voltage inverter IC that generates an adjustable –1.25V to –8V output from a single 3V–6.5V positive supply. It features external clock synchronization for noise-sensitive systems, 5% output regulation, 5mV typical output ripple, and shutdown mode reducing supply current to 0.2µA. It is used in GaAs FET bias generation and battery-powered instrumentation requiring clean, regulated negative rails.

For engineers reviewing the LTC1429CS datasheet, LTC1429CS pinout, LTC1429CS application, or LTC1429CS equivalent, key selection considerations include its SO-14 package, adjustable output configuration via ADJ/COMP pin, ±5% regulation tolerance, 700kHz typical sync clock frequency, and compatibility with tripler/doubler charge-pump topologies for flexible input-to-output voltage scaling.

Technical Context

The LTC1429CS implements a dual-mode charge-pump architecture-doubler (V_OUT ≈ –V_CC) and tripler (|V_OUT| ≈ 2×V_CC)-with external clock control via SYNC/SD. Its regulation loop uses two comparators: COMP1 (1.24V reference) for output voltage control and COMP2 (1.18V reference) to drive the open-drain REG flag when output is within ±5% of setpoint.

It supports external resistor-divider feedback at the ADJ pin for adjustable outputs or internal resistor-string configuration (R0/R1/RADJ pins) for fixed voltages like –3.5V, –4V, –4.5V, or –5V. Output ripple is minimized by optional 1000pF compensation capacitor from ADJ to ground and optimized flying/output capacitor selection (e.g., 0.1µF C1/C2, 3.3µF C_OUT).

Key Specifications

Pinout & Package

LTC1429CS is housed in a 14-pin plastic SOIC (SO-14) package with θ_JA = 150°C/W and operating junction temperature up to 150°C.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LTC1429CS8, the LTC1429CS supports adjustable outputs and tripler mode for wider input voltage compatibility, while LTC1550 trades external clock flexibility for lower ripple and integrated timing-making LTC1429CS optimal for noise-sensitive, clock-controlled systems requiring design adaptability.

Availability

LTC1429CS is available at Aetrix Electronics and suitable for GaAs FET bias generation, battery-powered instrumentation, and single-supply signal conditioning requiring stable component supply, long-term lifecycle support, and traceable sourcing.

Supply support for LTC1429CS 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 acquired Linear Technology in 2017 and maintains full technical and supply chain support for legacy Linear products including the LTC series.

The LTC1429CS belongs to Linear's precision switched-capacitor voltage converter family, designed specifically for noise-sensitive analog systems requiring regulated negative rails without inductors or transformers.

FAQ

What is the maximum input voltage the LTC1429CS can tolerate?

The LTC1429CS has an absolute maximum supply voltage rating of 9V on the VCC pin. However, for reliable operation in tripler mode, the total voltage between VCC and OUT must not exceed 12V. With outputs below –4.5V, the device may fall out of regulation at high loads or low input voltages; consult the Applications Information section for safe VCC–VOUT combinations. The LTC1429CS is rated for continuous operation from 3V to 6.5V.

Can the LTC1429CS generate –5V from a 3.3V supply?

Yes, the LTC1429CS can generate –5V from a 3.3V supply when configured in tripler mode using two 0.1µF flying capacitors (C1 between C1+/C1–, C2 between C2+/C2–). This configuration delivers up to 25mA at –5V with 5% regulation. The LTC1429CS datasheet confirms tripler-mode operation down to 3.3V input, making it suitable for single-cell Li-ion or low-voltage embedded systems requiring clean negative rails.

How does the REG pin function on the LTC1429CS?

The REG pin on the LTC1429CS is an open-drain N-channel output that pulls low when the magnitude of VOUT is within 5% of the set output voltage (e.g., –3.8V to –4.2V for a –4V target). It sinks up to 15mA at 5V VCC and requires an external pull-up resistor. The pin's drain can be pulled up to 12V above ground without damage, enabling direct interfacing with higher-voltage logic or discrete power-valid indicators in the LTC1429CS application.

What external capacitors are required for basic LTC1429CS operation?

A minimum of three external capacitors are required for basic LTC1429CS operation: one 0.1µF flying capacitor (C1) between C1+ and C1– for doubler mode, or two 0.1µF flying caps (C1 and C2) for tripler mode; one ≥0.1µF ceramic bypass capacitor on VCC; and one ≥3.3µF output capacitor (low-ESR tantalum or ceramic) on OUT. An optional 1000pF capacitor from ADJ/COMP to ground further reduces output ripple in the LTC1429CS design.

Is the LTC1429CS pin-compatible with the LTC1429CS8?

No, the LTC1429CS is not pin-compatible with the LTC1429CS8. The LTC1429CS uses a 14-pin SOIC package with dedicated C2+, C2–, R0, R1, and RADJ pins for tripler mode and adjustable/fixed output configuration, while the LTC1429CS8 uses an 8-pin SOIC package with only C1+, C1–, SYNC/SD, COMP, REG, OUT, VCC, and GND. Their pinouts, functionality, and external component requirements differ significantly-direct replacement requires PCB redesign.