onsemi FHR1200

Overview

FHR1200 from ON Semiconductor (formerly Fairchild) is a micro-power, ultra-wide-voltage shunt regulator IC used for precision voltage reference and feedback in isolated and non-isolated SMPS topologies. It delivers 7.5 V to 100 V programmable output, ±2% output voltage accuracy, -30 PPM/°C temperature coefficient, and operates with only 12 μA max quiescent current - enabling high-efficiency primary- and secondary-side regulation in smart meters and industrial motor control power supplies.

For engineers reviewing the FHR1200 datasheet, pinout, applications, or equivalent options, this page provides verified technical context, SC70-6 pin mapping, real-world regulation use cases, and validated alternative parts for flyback controller feedback loop design under wide-input-voltage and high-temperature conditions.

Technical Context

The FHR1200 implements a precision bandgap-referenced shunt regulator with integrated NPN transistor output stage, enabling direct drive of PWM controller feedback pins without optocouplers. Its architecture supports both fixed and programmable output configurations via external resistor dividers, with cathode current capability spanning 10 μA to 50 mA.

It features active temperature compensation yielding -30 PPM/°C typical drift, low 141 μV_rms output noise (400 Hz–100 kHz), and 4.47 MHz gain-bandwidth product - ensuring fast transient response and stable regulation across -55°C to +150°C ambient operation.

Key Specifications

Pinout & Package

Package: SC70-6 (SOT363), 1.25 mm wide, surface-mount, space-saving footprint with thermal resistance R_θJA = 550°C/W.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar shunt regulator applications.

Compared with TL431ACDBVR and LM4040CIM3-ADJ, the FHR1200 uniquely integrates a high-voltage NPN output stage, supports 100 V cathode operation at 12 μA I_Q, and delivers -30 PPM/°C drift - making it the only option among the three capable of direct, low-component-count, high-temperature regulation in >72 V SMPS systems.

Availability

FHR1200 is available at Aetrix Electronics and suitable for smart meter power supplies, industrial motor control auxiliary rails, and street lighting LED drivers requiring stable component supply across extended temperature and high-voltage operating conditions.

Supply support for FHR1200 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

ON Semiconductor (formerly Fairchild Semiconductor) is a global supplier of energy-efficient semiconductor solutions for automotive, industrial, cloud computing, and IoT applications.

The FHR1200 belongs to ON Semiconductor's high-voltage analog regulator product line, designed specifically for precision feedback and biasing in isolated and non-isolated switch-mode power supplies operating above 72 V and up to 100 V.

FAQ

What is the maximum cathode voltage the FHR1200 can regulate?

The FHR1200 supports a maximum regulator output (cathode) voltage of 100 V, as specified in its Absolute Maximum Ratings and confirmed in the Electrical Characteristics table. This 100 V rating applies to the C pin (Pin 6) relative to E (Pin 1), enabling direct use in high-input-voltage flyback converters without external clamping. The FHR1200 maintains ±2% output accuracy and stable regulation across its full 7.5 V to 100 V programmable range.

Does the FHR1200 require an external transistor to drive a PWM controller feedback pin?

No, the FHR1200 does not require an external transistor - it integrates a high-voltage NPN output stage that directly sinks up to 50 mA at the C pin (Pin 6), allowing it to drive the feedback (FB) pin of PWM controllers such as the UCC287xx or NCP101x families. This capability eliminates the need for optocouplers or discrete transistors in both isolated and non-isolated secondary-side regulation, a key differentiator from standard shunt references like the TL431. The FHR1200 achieves this while consuming only 12 μA max quiescent current.

What is the thermal performance of the FHR1200 in SC70-6 package?

The FHR1200 in SC70-6 (SOT363) package has a junction-to-air thermal resistance (R_θJA) of 550°C/W and a junction-to-board parameter (Ψ_JB) of 370°C/W, measured on a standard FR4 PCB (76 × 114 × 0.6 mm). Its maximum power dissipation is 227 mW at T_A = 25°C, derating linearly above that temperature per Figure 19. These values confirm suitability for compact, thermally constrained layouts in smart meter and LED driver applications where airflow is limited. The FHR1200 remains fully operational from -55°C to +150°C junction temperature.

Can the FHR1200 be used for primary-side regulation without an optocoupler?

Yes, the FHR1200 is explicitly designed for primary-side regulation (PSR) in flyback converters without an optocoupler. Its ability to directly drive PWM controller feedback pins - combined with programmable output up to 100 V, -30 PPM/°C temperature coefficient, and operation from -55°C to +150°C - enables accurate, isolated output voltage sensing via transformer auxiliary winding or capacitive coupling. Application Figures 21 and 22 in the FHR1200 datasheet validate this use case for both PSR and non-isolated secondary-side regulation.

What is the purpose of Pin 2 (N.C.) on the FHR1200?

Pin 2 of the FHR1200 is designated N.C. (No Connection) and is internally unconnected - it serves no electrical function and must be left floating or omitted from the PCB layout. This is confirmed in the Pin Definitions section of the FHR1200 datasheet (Rev. 1.0.1, p.2), which states "N.C." under Pin Name and "No Connection" under Description. Unlike functional pins such as K (reference), C (cathode), or A/B (bias), Pin 2 has no internal bond wire or circuit node; routing or grounding it may introduce parasitic coupling or contamination risk.