Overview

The HT16K33 is a memory-mapped and multi-function LED controller IC manufactured by Holtek Semiconductors. Communicating via an I2CI^2C bus interface (400 kHz400\text{ kHz} Fast Mode), it can drive up to 128 individual LEDs (16×816 \times 8 matrix or up to 8 digits of 7-segment / 14-segment displays) while simultaneously scanning a 13×313 \times 3 key matrix.

Equipped with an internal RC oscillator, 16-step global PWM dimming control, and hardware I2CI^2C address selection jumpers (0x70…0x770\text{x}70 \dots 0\text{x}77), the HT16K33 is the standard driver IC powering Adafruit's 7-segment display backpacks, 14-segment alphanumeric displays, and 8×88 \times 8 dot matrix LED modules.

Quick reference

Operating Voltage (VDD)4.5 V to 5.5 V DC (I2C SDA/SCL lines 3.3V compatible)
Max LED Output Capacity128 LEDs (16 Anodes×8 Cathodes16 \text{ Anodes} \times 8 \text{ Cathodes})
Keyscan CapabilityUp to 39 switches (13×313 \times 3 matrix)
PWM Dimming Control16 Levels (1/161/16 to 16/1616/16 duty cycle)
I2C Bus Speed100 kHz100\text{ kHz} Standard Mode / 400 kHz400\text{ kHz} Fast Mode
I2C Address Range0x700\text{x}70 to 0x770\text{x}77 (Configured via A0, A1, A2 jumpers)
Package28-pin SOP / 24-pin SOP / Breakout Module

Pinout & Module Terminals

SOP-28 Package IC

text
             ┌───┴───┐
       VSS 1 │ 1   28│ VDD
     COM0 2  │       │ 27 ROW15 / A15
     COM1 3  │       │ 26 ROW14 / A14
     COM2 4  │       │ 25 ROW13 / A13
     COM3 5  │ HT16K │ 24 ROW12 / A12
     COM4 6  │  33   │ 23 ROW11 / A11
     COM5 7  │       │ 22 ROW10 / A10
     COM6 8  │       │ 21 ROW9 / A9
     COM7 9  │       │ 20 ROW8 / A8
   ROW0/A0 10│       │ 19 SCL
   ROW1/A1 11│       │ 18 SDA
   ROW2/A2 12│       │ 17 VDD
   ROW3/A3 13│       │ 16 INT / KEY INT
   ROW4/A4 14│       │ 15 ROW5 / A5
             └───────┘

Module Header Terminals (Adafruit LED Backpack)

TerminalFunctionDescription
VCCPowerSupply Voltage (+4.5V to +5.5V DC)
GNDPowerSystem Ground (0 V)
SDAI2C DataSerial Data line (Connect to MCU SDA; 3.3V / 5V tolerant)
SCLI2C ClockSerial Clock line (Connect to MCU SCL; 3.3V / 5V tolerant)
A0, A1, A2JumpersSolder jumpers to change I2C address from default 0x700\text{x}70

Specifications

ParameterSymbolMinTypMaxUnitConditions
Supply VoltageVDDV_{DD}4.55.05.5VDC
Operating CurrentIDDI_{DD}—2.04.0mANo load, VDD=5VV_{DD} = 5\text{V}
Standby CurrentISTBI_{STB}—0.110.0µAStandby mode
I2C Clock FrequencyfSCLf_{SCL}——400kHzVDD=5VV_{DD} = 5\text{V}
Segment Drive CurrentISEGI_{SEG}202530mAVDD=5V,VOUT=VDD−1.0VV_{DD} = 5\text{V}, V_{OUT} = V_{DD}-1.0\text{V}
COM Drive CurrentICOMI_{COM}120150180mAVDD=5V,VOUT=0.6VV_{DD} = 5\text{V}, V_{OUT} = 0.6\text{V}

Wiring & Code Example (Arduino)

text
   HT16K33 Backpack                        Arduino Uno
    [ VCC ] ───────────────────────────── 5V
    [ GND ] ───────────────────────────── GND
    [ SDA ] ───────────────────────────── A4 (SDA)
    [ SCL ] ───────────────────────────── A5 (SCL)
cpp
#include <Wire.h>
#include <Adafruit_GFX.h>
#include "Adafruit_LEDBackpack.h"

Adafruit_7segment matrix = Adafruit_7segment();

void setup() {
  matrix.begin(0x70); // Initialize HT16K33 at I2C address 0x70
  matrix.setBrightness(10); // Set brightness (0 to 15)
  matrix.print(1234, DEC);
  matrix.writeDisplay();
}

void loop() {}

Common mistakes

  • Forgetting System Clock Enable command over I2C: The HT16K33 powers up in standby mode with its internal RC oscillator disabled. You must issue the System Setup command 0x21 (Oscillator ON) followed by Display Setup command 0x81 (Display ON, No Blink) over I2C before any LEDs will turn on.
  • Wrong I2C address: The default I2C address is 0x700\text{x}70 (when A0, A1, A2 solder jumpers are open). If solder jumpers are bridged, the address shifts up to 0x770\text{x}77. Run an I2C scanner sketch if the display fails to respond.
  • Powering from 3.3V without checking VDD range: Official HT16K33 spec lists VDD=4.5V…5.5VV_{DD} = 4.5\text{V} \dots 5.5\text{V}. While 3.3V logic signals on SDA/SCL work fine, powering VDDV_{DD} itself from 3.3V may leave blue or white LEDs under-powered due to their higher forward voltage drop (Vf≈3.2VV_f \approx 3.2\text{V}).

Notes

  • HT16K33 vs MAX7219 vs TM1637: HT16K33 uses I2C (0x700\text{x}70) and drives 128 LEDs (16×816 \times 8); MAX7219 uses SPI and drives 64 LEDs (8×88 \times 8); TM1637 uses a 2-wire custom bitbang protocol for 6 digits.

Assets & downloads