NXP Semiconductors HEF4794BT-Q100118

Overview

HEF4794BT-Q100 from Nexperia is an automotive-qualified 8-stage serial-in/parallel-out shift-and-store register with open-drain LED driver outputs (QP0–QP7), dual serial outputs (QS1/QS2), and independent strobe (STR) and output enable (OE) controls. It operates from 3 V to 15 V, supports -40 °C to +125 °C ambient, and delivers 40 mA per output for direct LED sinking in dashboard backlighting and status indicator arrays.

For engineers reviewing the HEF4794BT-Q100 datasheet, HEF4794BT-Q100 pinout, HEF4794BT-Q100 application, or HEF4794BT-Q100 equivalent, this page provides verified functional architecture, SO16 pin mapping, AEC-Q100 Grade 1 qualification evidence, propagation delay timing at 5/10/15 V, and validated alternatives for automotive serial-to-parallel LED control systems.

Technical Context

The HEF4794BT-Q100 implements a two-stage pipeline: an 8-bit shift register accepting serial data on CP rising edges, followed by an 8-bit storage latch loaded synchronously on STR HIGH. Outputs QP0–QP7 are open-drain with 40 mA sink capability and 1.5 V VOL at 20 mA (15 V supply). QS1 and QS2 provide cascading support - QS1 outputs shifted data on CP↑, while QS2 outputs the same data on the subsequent CP↓, enabling robust daisy-chaining under varying clock edge integrity conditions.

It features fully static CMOS operation, 5 V/10 V/15 V parametric ratings, and AEC-Q100 Grade 1 qualification confirmed across -40 °C to +125 °C. Input thresholds scale with VDD (VIH = 0.7×VDD min, VIL = 0.3×VDD max), and dynamic power dissipation is calculated via PD = K×fi + Σ(fo×CL)×VDD², where K = 15000 μW/MHz at 15 V.

Key Specifications

Pinout & Package

HEF4794BT-Q100 is housed in a plastic small outline package (SO16) per SOT109-1, with 16 leads, 3.9 mm body width, and JEDEC MS-012 compliance. Pin 1 is index-marked; pin 8 is VSS (ground); pin 16 is VDD (supply).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 8-bit shift-and-store LED driver applications.

Compared with HEF4794BT-Q100, TLC6C5912QPWRQ1 offers superior current accuracy but adds protocol overhead and cost, while TPIC6B595QPWRQ1 delivers higher drive strength at the expense of missing QS2-based clock-edge compensation - making HEF4794BT-Q100 optimal for cost-sensitive, cascaded 5–15 V automotive LED arrays requiring robust timing margin.

Availability

HEF4794BT-Q100 is available at Aetrix Electronics and suitable for automotive instrument clusters, interior lighting control systems, and HVAC panel indicators requiring stable component supply, AEC-Q100 compliance, and long-term production continuity.

Supply support for HEF4794BT-Q100 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

Nexperia is a global semiconductor expert focused on essential efficiency technologies, delivering high-performance logic, discrete, and MOSFET solutions for automotive, industrial, and consumer markets.

The HEF4794BT-Q100 belongs to Nexperia's automotive-qualified logic portfolio, designed specifically for robust serial-to-parallel LED control in harsh environments where reliability, wide supply range, and AEC-Q100 validation are mandatory.

FAQ

What is the maximum clock frequency supported by the HEF4794BT-Q100?

The HEF4794BT-Q100 supports a maximum clock frequency (fclk(max)) of 28 MHz at VDD = 15 V, 22 MHz at 10 V, and 10 MHz at 5 V. These values are specified in Table 7 of the datasheet and reflect guaranteed timing margins under recommended operating conditions. The HEF4794BT-Q100 achieves this performance through optimized CMOS gate design and low-propagation-delay internal paths, enabling high-speed LED refresh in real-time automotive displays.

Does the HEF4794BT-Q100 require external pull-up resistors on its QPn outputs?

Yes, the HEF4794BT-Q100 QP0–QP7 outputs are open-drain and require external pull-up resistors to VDD or another positive rail to establish HIGH-state voltage levels for LED anodes or logic interfacing. The value depends on desired LED current and VDD; for example, a 150 Ω resistor with 12 V VDD yields ~80 mA - exceeding the 40 mA absolute maximum per output, so 300 Ω or higher is typical. The HEF4794BT-Q100 datasheet confirms this requirement in Section 1 and Figure 11.

How does the dual serial output (QS1 and QS2) functionality improve system reliability in cascaded configurations?

QS1 outputs data on CP rising edges, while QS2 outputs the same data on the subsequent CP falling edge - decoupling cascaded device timing from clock slew rate. This allows reliable daisy-chaining even with slow-rising clocks (where QS2 prevents setup-time violations) or fast-rising clocks (where QS1 minimizes latency). The HEF4794BT-Q100 functional description explicitly defines this behavior in Section 1 and Figure 2, making it uniquely robust for automotive wiring harnesses with variable signal integrity.

Is the HEF4794BT-Q100 pin-compatible with the non-automotive HEF4794B series?

Yes, the HEF4794BT-Q100 shares identical pinout, electrical characteristics, and functional behavior with the commercial-grade HEF4794B (e.g., HEF4794BT), as confirmed in Nexperia's ordering information table and pin description section. The "-Q100" suffix denotes AEC-Q100 qualification and extended temperature screening - not a pinout or logic change. Therefore, HEF4794BT-Q100 can be used as a drop-in replacement in existing designs requiring automotive qualification, provided thermal and lifetime validation is performed.

What is the purpose of the strobe (STR) input in the HEF4794BT-Q100, and how does it differ from the clock (CP) input?

The STR input controls transfer from the 8-bit shift register to the 8-bit storage latch - effectively freezing the parallel output state during ongoing serial shifting. CP advances bits through the shift register only; STR updates QP0–QP7 simultaneously. This separation prevents partial updates and visual artifacts in LED arrays. The HEF4794BT-Q100 function table (Table 3) and timing diagram (Figure 4) confirm STR's role as the output latch enable, distinct from CP's serial shift function.