Texas Instruments LP3943ISQ

Overview

LP3943ISQ from Texas Instruments is a 16-channel SMBus/I²C-controlled LED driver IC with independent per-channel dimming control, 25mA sink capability per output, internal precision oscillator (0.625Hz–160Hz), and programmable PWM frequency/duty cycle via two prescaler-PWM register pairs. It serves as an RGB/white-LED lighting controller and GPIO expander in space-constrained portable electronics.

For engineers reviewing the LP3943ISQ datasheet, LP3943ISQ pinout, LP3943ISQ application, or LP3943ISQ equivalent, this page delivers verified technical context, exact package mapping (WQFN-24), confirmed I²C timing compliance (400kHz), real-world thermal metrics (RθJA = 45.0°C/W), and validated alternative part selection guidance for LED driver design and BOM optimization.

Technical Context

The LP3943ISQ integrates a precision internal oscillator and dual 8-bit prescaler-PWM register pairs (PSC0/PWM0 and PSC1/PWM1), enabling independent dimming rates across two groups of up to eight LEDs each. Each of its 16 open-drain outputs supports programmable states: high-impedance (Hi-Z), active-low ON, or dimming at either DIM0 or DIM1 rate.

It implements SMBus/I²C protocol with auto-increment addressing, 7-bit slave address selectable via A0–A2 pins (base address 0x60–0x67), and supports write-only chip addressing followed by register-addressed data writes. The device features power-on reset (VPOR = 1.96V) and active-low asynchronous reset (RST), ensuring deterministic initialization without external circuitry.

Key Specifications

Pinout & Package

LP3943ISQ is housed in a 4.00mm × 4.00mm WQFN-24 package (RTW) with exposed thermal pad tied internally to GND. The 24-pin top-view layout includes 16 dedicated LED sink outputs, 3 address inputs (A0–A2), I²C interface (SCL/SDA), active-low reset (RST), power (VDD), ground (GND), and no unused or NC pins.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar LED driver applications.

Compared with TLC59284DBQR and PCA9635PW, the LP3943ISQ uniquely combines 8-bit PWM resolution, internal oscillator, Hi-Z output state for GPIO use, and I²C auto-increment - making it optimal for cost-sensitive, space-constrained designs requiring both lighting control and I/O expansion.

Availability

LP3943ISQ is available at Aetrix Electronics and suitable for cellular phone indicator lighting, digital camera status feedback, and portable audio UI lighting requiring stable component supply and long-term production continuity.

Supply support for LP3943ISQ 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

Texas Instruments is a global semiconductor company specializing in analog and embedded processing solutions, with leadership in power management, signal chain, and interface technologies.

The LP3943ISQ belongs to TI's LED driver product line, designed specifically for low-power, multi-channel LED control in portable consumer electronics where I²C efficiency, small footprint, and integrated timing are essential.

FAQ

What is the maximum total current the LP3943ISQ can sink across all channels?

The LP3943ISQ supports up to 25mA per LED output pin, with a hard limit of 200mA total package current. This is enforced by thermal design - exceeding 200mA risks junction temperature rise beyond 125°C under typical PCB conditions. Each octal group (LED0–LED7 and LED8–LED15) must not exceed 100mA. The LP3943ISQ datasheet specifies these limits in Section 5.5 Electrical Characteristics and Figure 7-3 LED switch resistance curves.

Does the LP3943ISQ require an external crystal or clock source?

No, the LP3943ISQ does not require an external crystal or clock source. It contains an internal precision oscillator that generates all timing signals needed for PWM dimming and I²C interface operation. The oscillator supports frequencies from 0.625Hz to 160Hz and maintains stability across −40°C to +85°C ambient temperature, as confirmed in Section 6.3 Feature Description and Figure 5-1 Frequency vs. Temperature.

How many I²C addresses can be assigned to the LP3943ISQ?

The LP3943ISQ supports eight unique I²C slave addresses (0x60 through 0x67) via the A0, A1, and A2 address-select pins. These pins configure the three least-significant bits of the fixed 7-bit address (bits 6–4 are hardwired to '110'). All combinations are valid and electrically isolated - no conflict occurs between devices sharing the same bus when A0–A2 are set to distinct values. This is documented in Section 6.5.3 Transferring Data and Figure 6-3 Chip Address Byte.

Can unused LED output pins on the LP3943ISQ be used as general-purpose I/O?

Yes, unused LED output pins on the LP3943ISQ can be configured as general-purpose open-drain I/O. By setting the corresponding bits in LS0–LS3 selector registers to '00', the pin enters high-impedance (Hi-Z) state; setting them to '01' drives the pin low. This GPIO functionality is explicitly supported in the device architecture and described in Section 6.4 Device Functional Modes and Section 6.6.3 Binary Format for Selector Registers.

What is the recommended decoupling capacitance for the LP3943ISQ VDD pin?

Texas Instruments recommends placing a 1µF ceramic capacitor as close as possible to the VDD pin and GND for stable operation. This value is specified in Section 5 Layout and illustrated in Figure 7-6 Layout Example. The capacitor mitigates noise coupling from switching LED currents and ensures clean power delivery during I²C communication bursts, especially under dynamic load conditions.