BETADisplay capacity6 digits × 8 segments
Six-digit LED driver with key scanning
TM1637 Specifications
Review TM1637 electrical specifications, operating conditions and package details.
Package view
Key specifications
The host writes one segment byte per grid position. The internal oscillator scans the digits, PWM controls brightness and the shared segment outputs also scan the optional key matrix.
Example supply5 V
Key matrix16 keys · one reported at a time
PWM settings8 non-linear levels
Package details
TM1637 · DIP-20
| Property | Details |
|---|---|
| Manufacturer | Titan Micro Electronics |
| Part number | TM1637 |
| Package | DIP-20 |
| Connections | 20 pins |
| Mounting | Through-hole |
| Lead pitch | 2.54 mm |
| Package code | DIP-20 |
| Thermal reference | See operating and package limits |
Supply and electrical conditions
Distinguish operating conditions from absolute limits
Manufacturer specifications 8 parameters
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| Parameter | Value | Conditions / notes |
|---|---|---|
| Nominal application supply | 5 V | V2.4 reference circuit |
| Electrical/timing test supply | 4.5–5.5 V | Published characteristics use this range |
| Input HIGH / LOW | ≥0.7 × VDD / ≤0.3 × VDD | At 5 V: ≥3.5 V HIGH, ≤1.5 V LOW |
| Operating temperature | −40 to +85°C | Board and LED heating must remain within limits |
| No-load current, display OFF | 5 mA maximum | Not total LED supply current |
| Internal oscillator | 450 kHz typical | RC oscillator; display scan is automatic |
| Bypass example | 100 nF ceramic + 100 µF bulk | Place close to VDD16 / GND1 |
| Absolute limits | 7 V supply; 400 mW dissipation | Damage limits, not recommended operating settings |
No specifications match. Try a parameter name or a unit.
Use a compatible host or proper level translation; a 3.3 V HIGH is not guaranteed at a 5 V supply.
Display and key commands
Each command byte is sent LSB first
Manufacturer specifications 8 parameters
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| Parameter | Value | Conditions / notes |
|---|---|---|
| 0x40 | Write display, auto increment | Normal mode; addresses advance through six bytes |
| 0x44 | Write display, fixed address | Send the chosen address and one byte |
| 0x42 | Read key-scan code | Release DIO for IC-to-host transfer |
| 0xC0–0xC5 | Set display address | GRID1 through GRID6 respectively |
| 0xC6 and higher | Outside display RAM | Data ignored until a valid address is selected |
| 0x80 | Display OFF | Output blanking command |
| 0x88–0x8F | Display ON + brightness | Low three bits select the PWM setting |
| Test mode bit | Keep cleared | Reserved for manufacturer testing |
No specifications match. Try a parameter name or a unit.
There is no I²C slave address or decimal-to-segment decoder.
Segment bytes and example digits
Example wiring: SEG1…SEG8 = A, B, C, D, E, F, G, DP
Manufacturer specifications 7 parameters
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| Parameter | Value | Conditions / notes |
|---|---|---|
| Byte D0…D7 | SEG1…SEG8 | A set bit enables its segment |
| Blank / dash | 0x00 / 0x40 | Dash uses only segment G |
| Digits 0, 1, 2, 3 | 0x3F, 0x06, 0x5B, 0x4F | For the stated segment wiring |
| Digits 4, 5, 6, 7 | 0x66, 0x6D, 0x7D, 0x07 | No automatic font decoding |
| Digits 8, 9 | 0x7F, 0x6F | Decimal point remains off |
| Decimal point | OR the byte with 0x80 | Some modules wire this output to a colon instead |
| Six-digit example 123456 | 06 5B 4F 66 6D 7D | Send after 0xC0 with auto increment enabled |
No specifications match. Try a parameter name or a unit.
A breakout module can have a different digit or colon map; check its wiring.
Eight PWM brightness settings
Duty applies during the selected digit slot
Manufacturer specifications 8 parameters
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| Parameter | Value | Conditions / notes |
|---|---|---|
| 0x88 / level 0 | 1/16 | Display ON; minimum PWM |
| 0x89 / level 1 | 2/16 | |
| 0x8A / level 2 | 4/16 | |
| 0x8B / level 3 | 10/16 | The step from level 2 is intentionally large |
| 0x8C / level 4 | 11/16 | |
| 0x8D / level 5 | 12/16 | |
| 0x8E / level 6 | 13/16 | |
| 0x8F / level 7 | 14/16 | Maximum PWM setting |
No specifications match. Try a parameter name or a unit.
PWM duty is not the complete per-LED average duty: digit multiplexing also applies.
Two-wire timing
Use the conservative 100 kHz example for both writing and key reads
Manufacturer specifications 8 parameters
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| Parameter | Value | Conditions / notes |
|---|---|---|
| START / STOP | DIO falls / rises while CLK HIGH | Keep DIO stable during ordinary HIGH clock periods |
| Bit order | Least-significant bit first | Different from many SPI devices |
| Acknowledge | Ninth clock; DIO pulled LOW | Host releases DIO after bit 7 |
| Write clock upper specification | 500 kHz at 50% duty | Electrical table maximum, subject to timing limits |
| Key-read clock | Below 250 kHz | Additional instruction in the key-read section |
| Clock pulse width | At least 400 ns | Observe all other timing constraints too |
| Data setup / hold | At least 100 ns / 100 ns | Relative to CLK |
| Waiting time | At least 1 µs | CLK rising to falling in the timing table |
No specifications match. Try a parameter name or a unit.
The 100 kHz demonstration provides margin for pull-ups, wiring capacitance and host timing.
Key scan and output loading
Optional 8 × 2 matrix shares the segment scan lines
Manufacturer specifications 8 parameters
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| Parameter | Value | Conditions / notes |
|---|---|---|
| K1 / K2 contacts | Pins 19 / 20 | Two key-return inputs |
| Idle key code | 0xFF | No key reported |
| Simultaneous keys | Not supported | Do not assume rollover or independent key bits |
| Key input bias | 10 kΩ nominal internal pull-down | Unused K1/K2 can remain unconnected |
| Segment sink capability | 20 / 30 / 50 mA min / typ / max | At VO=0.3 V in the electrical table |
| Grid source capability | 80 / 120 / 180 mA min / typ / max | At VO=VDD−2 V |
| Current interpretation | These are output-characteristic test values | Not a guaranteed constant-current setting or a free current budget |
| Display loading | Check LED pulse limits and IC dissipation | Use segment resistors when required by the selected display/current design |
No specifications match. Try a parameter name or a unit.
Unlike MAX7219, TM1637 has no external RSET pin; do not copy the MAX7219 current-setting circuit.
Connections by function
Select a pin for its function, connection guidance and electrical notes.