Renesas HA1835P-01

Overview

HA1835P from Renesas Electronics (formerly Hitachi) is a monolithic watchdog timer and voltage regulator controller IC for microcomputer systems. It integrates regulated 5 V output (4.75–5.25 V), power-on reset (80–200 ms), and pulse-width-detect watchdog timer with external Rf/Cf programmable bandpass filter, operating from 6–30 V supply. It drives external PNP transistors for high-current regulation and supports both low- and high-level reset microcontrollers.

For engineers reviewing the HA1835P datasheet, HA1835P pinout, HA1835P application, or HA1835P equivalent, this page delivers verified functional identity, validated pin roles, confirmed reset timing ranges, regulator load/line regulation specs, and real-world watchdog sensitivity configuration - all critical for embedded safety-critical power sequencing and fail-safe monitoring design.

Technical Context

The HA1835P implements a dual-path reset architecture: a power-on reset detector using external RR/CR (60–220 ms off-time, 80–200 ms on-time) and a watchdog timer with bandpass filter-based pulse validation via P-RUN input. Its regulator section uses error amplifier feedback through Vadj to adjust output between 4 V and 6 V, while CS pin enables current limiting via external sense resistor (RSC ≈ 0.3 V / I_OUT(LIMIT)).

It features open-collector RES and RES outputs requiring ~5 kΩ pull-up resistors, internal overcurrent protection for external PNP transistors, and phase compensation at Comp pin (≤100 pF capacitor to VCC). HA1835P excludes pin 9 (Comp), distinguishing it from HA1848P which leaves pin 9 unconnected.

Key Specifications

Pinout & Package

HA1835P uses a 14-pin DP-14 (Dual In-line Plastic) package per Hitachi JEDEC/EIAJ-compliant outline, mass 0.97 g, lead pitch 2.54 mm, body width 7.62 mm, length 19.20 mm.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar watchdog timer and regulator controller applications.

Compared with MAX6326US29D3+ and TPS3823-33DBVR, HA1835P uniquely integrates regulator control, dual-mode reset, and programmable watchdog in one 14-pin package - eliminating three discrete components and enabling robust, self-contained fail-safe power management for 5 V microcomputer systems.

Availability

HA1835P is available at Aetrix Electronics and suitable for industrial automation, automotive electronics, medical device, and smart metering applications requiring stable component supply, long-term lifecycle support, and guaranteed fail-safe reset functionality.

Supply support for HA1835P 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

Renesas Electronics Corporation is a global semiconductor leader formed from the merger of NEC Electronics and Renesas Technology, delivering microcontrollers, analog, power, and timing solutions for industrial, automotive, and IoT markets.

The HA1835P belongs to Hitachi's legacy analog power management product line, designed specifically for microcomputer systems needing integrated voltage regulation, power-on reset, and hardware watchdog supervision in harsh environments.

FAQ

What is the function of the Comp pin on HA1835P?

The Comp pin on HA1835P is the phase compensation terminal for the internal voltage regulator error amplifier. A capacitor of ≤100 pF must be connected between Comp and VCC to ensure loop stability and prevent oscillation under varying load conditions. This pin is actively used in HA1835P, unlike HA1848P where it is unconnected.

Can HA1835P drive a PNP transistor directly, and what is the maximum supported current?

Yes, HA1835P directly drives the base of an external PNP transistor via the VCONT pin, with built-in current limiting. The IC supports external PNP transistors delivering up to 1 A output current, protected by the CS pin current-sense circuit (ICS = 1.0–2.0 A threshold) and internal overcurrent limiter.

How do I configure HA1835P for a 4.5 V output voltage?

To set HA1835P output to 4.5 V, connect a resistor between Vadj and GND. Using the formula R(Vadj–GND) ≈ (7.14 × (Vout − 5)) / (5 − Vout) kΩ, a ~2.4 kΩ resistor yields ~4.5 V. Confirm with load testing, as Vout tolerance is ±250 mV at 1 A per datasheet.

What is the difference between RES and RES pins on HA1835P?

RES is an active-low open-collector reset output for microcontrollers requiring low-level reset assertion; RES is an active-high open-collector reset output for those requiring high-level assertion. Both require ~5 kΩ external pull-up resistors and share identical timing characteristics (tRL = 40–160 ms, tRH = 50–200 ms).

Does HA1835P support watchdog timeout adjustment independent of power-on reset timing?

Yes, HA1835P supports fully independent adjustment: power-on reset timing is set by RR and CR, while watchdog timeout is set by Rf and Cf. These RC networks operate in separate internal circuits - allowing distinct configuration for boot reliability (e.g., 150 ms ton) and runtime fault detection (e.g., 100 ms clock-off window).