MAX7219CNG

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1. Description

The MAX7219CNG are compact, serial input/output common-cathode display drivers that interface microprocessors (μPs) to 7-segment numeric LED displays of up to 8 digits, bar-graph displays, or 64 individual LEDs. Included on-chip are a BCD code-B decoder, multiplex scan circuitry, segment and digit drivers, and an 8x8 static RAM that stores each digit. Only one external resistor is required to set the segment current for all LEDs. The MAX7221 is compatible with SPI™, QSPI™, and MICROWIRE™, and has slew-rate-limited segment drivers to reduce EMI. A convenient 4-wire serial interface connects to all common μPs. Individual digits may be addressed and updated without rewriting the entire display. The MAX7219/MAX7221 also allow the user to select code-B decoding or no-decode for each digit. The devices include a 150μA low-power shutdown mode, analog and digital brightness control, a scan-limit register that allows the user to display from 1 to 8 digits, and a test mode that forces all LEDs on. For applications requiring 3V operation or segment blinking, refer to the MAX6951 data sheet.

2. Features

    1. 10MHz Serial Interface

    2. Individual LED Segment Control

    3. Decode/No-Decode Digit Selection

    4. 150μA Low-Power Shutdown (Data Retained)

    5. Digital and Analog Brightness Control

    6. Display Blanked on Power-Up

    7. Drive Common-Cathode LED Display

    8. Slew-Rate Limited Segment Drivers for Lower EMI (MAX7221)

    9. SPI, QSPI, MICROWIRE Serial Interface (MAX7221)

  10. 24-Pin DIP and SO Packages

3. Applications

    1. Bar-Graph Displays

    2. Industrial Controllers

    3. Panel Meters

    4. LED Matrix Displays

4. Pin Configuration

5. Pin Description

6. Application information

1. Power supply bypass and wiring

Minimize power supply ripple due to peak figures Drive current, connect a 10μF electrolyte and a 0.1μF The ceramic capacitor between V+ and GND is as close as possible Equipment as much as possible. MAX7219CNG/MAX7221 should be Place close to the LED display and connect Should be as short as possible to reduce impact Line inductance and electromagnetic interference. In addition, both GND pins must be grounded.

2. Choose RSET resistor and use external driver

Each segment current is about 100 times Current in ISET. To select RSET, see Table 11. Maximum recommended segment of MAX7219CNG/MAX7221 The current is 40mA. For higher segment current levels These levels will require external digital drivers. At this In application, MAX7219/MAX7221 are only used as Other high-current drivers or transistor controllers. Therefore, in order to save power, use RSET = 47kΩ in the following cases Use an external current source as a segment driver. Use MAX7219/MAX7221 Segment drive, MAX394 single pole double throw Analog switch and external transistor for driving 2.3”AND2307SLC common cathode display. 5.6V Zener diode The diode is connected in series with a decimal point LED because the decimal point LED forward voltage is Usually 4.2V. For all other segments, the LED is forward The voltage is usually 8V. Since the external transistor is Used to sink current (DIG 0 and DIG 1 are used as logic Switch), allowing a peak current of 45mA Even if only two digits are displayed.