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MAX14521E Datasheet(PDF) 10 Page - Maxim Integrated Products |
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MAX14521E Datasheet(HTML) 10 Page - Maxim Integrated Products |
10 / 21 page Boost Converter The MAX14521E boost converter consists of an exter- nal- tapped inductor from VDD to the LX input, an internal DMOS switch, an external diode from the secondary of the tapped inductor to the CS output, an external capaci- tor from the CS output to GND, and an EL lamp con- nected to the EL lamp outputs. When the DMOS switch is turned on, LX is connected to GND, and the inductor is charged. When the DMOS switch is turned off, the energy stored in the inductor is transferred to the capacitor CCS and the EL lamp. Note: The MAX14521E exhibits high-voltage spikes on the LX node. The addition of a snubber circuit to the LX node protects the device by suppressing the highvoltage spikes. The values of RSN and CSN should be optimized for the specific tapped inductor used. Typical values are RSN = 20Ω and CSN = 330pF. The MAX14521E boost-converter frequency uses an internal oscillator to set the frequency of the boost converter. The oscillator frequency is adjusted by the FSW[4:0] bits of the boost-converter frequency register. The boost converter increases and decreases linearly with FSW[3:0]. To further reduce the amount of EMI/EFI generated by the circuit, the boost-converter frequency can be modulated (see the SS[1:0] bits of the boost-converter frequency register). Enabling modulation spreads the switching energy of the oscillator in the frequency domain, thus decreasing EMI. Independent Dimming Control The brightness of an EL lamp is proportional to the peak- to-peak voltage applied across the lamp. The MAX14521E provides four registers to control the EL peak-to-peak volt- age of each EL output using the EL_ _[4:0] bits of the EL ramping time and EL peak voltage registers. EL Output Waveshape The MAX14521E can produce sine-wave to squarewave waveshapes on the EL output by varying the slope of the EL output. This is achieved by using bits SL[1:0] of the EL shape register. If the EL shape configuration is set to sine and if all EL outputs have the same amplitude settings, then each EL output has a sinusoidal waveshape. If the EL outputs have different amplitude settings, then the EL output with the highest setting has a sine waveshape while the remaining EL outputs have a clamped sine waveshape. Auxiliary Audio Input (AUX) The MAX14521E uses an auxiliary input AUX that accepts an audio signal to produce visual effects on the EL out- puts. The frequency and amplitude modulation (FR_AM) bit is set to modulate the EL output voltage or frequency. The AUX audio signal modulates the EL output voltage when FR_AM is set to 0 and modulates the EL output frequency when FR_AM is set to 1. When the NO_SAMPLE bit is enabled, the voltage of the EL outputs is proportional to the voltage at AUX. For example, when FR_AM = 0, NO_SAMPLE = 1, and any of the AU1, AU2, AU3, AU4 bits are set to 1, the peak value of those particular channels follow AUX directly. If AUX is a DC value, the EL output voltage is VEL = 250 x AUX (VP-P) with a maximum of 300VP-P. AUX can also accept a PWM signal with a frequency rang- ing from 100kHz to 10MHz, where the EL output voltage is VEL = 300 x DutyCycle% (VP-P). The NO_SAMPLE bit has no effect when FR_AM = 1. When FR_AM = 1, frequency modulation is enabled and the AUXDIV1 and AUXDIV0 bits are used to divide the audio frequency and apply this to the EL outputs. AU1, AU2, AU3, and AU4 must be set to 1 to enable this feature. Shutdown The MAX14521E features two methods to place the device in shutdown: 1) a reset input, RB, to clear all reg- isters to zero and put the device into low-power shutdown mode, and 2) the EN bit of the system register. Using method 1, the device does not respond to I2C commu- nications when RB is held low. Using method 2, the EL outputs are shut down; however, the register contents remain unchanged. Undervoltage Lockout (UVLO) The MAX14521E has a UVLO threshold of +2.0V (typ). When VDD falls below +2.0V (typ), the device enters a nonoperative mode. The contents of the I2C registers are not guaranteed below UVLO. Thermal Protection The MAX14521E enters a nonoperative mode if the internal die temperature of the device reaches or exceeds +160°C (typ). The MAX14521E is latched, and only placing RB to 0 resets the thermal protection bit as well as all registers. MAX14521E Quad, High-Voltage EL Lamp Driver with I2C Interface www.maximintegrated.com Maxim Integrated │ 10 |
Similar Part No. - MAX14521E_15 |
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Similar Description - MAX14521E_15 |
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