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SP7616 Evaluation Board Manual
LED Drivers for parallel connected LED Ultra Low Dropout Voltage of 150mV No EMI, no switching noise Integrated current matching PWM and Analog brightness control Enable/Shutdown control Shutdown current < 1A
SP7616 Eval Board Top Side (not to scale)
DESCRIPTION AND BOARD SCHEMATIC
This Evaluation Board is designed to help the user evaluate performance of the SP7616 for use as a LED Driver. The evaluation board is a completely assembled and tested surface mount board which provides easy probe access points to all inputs and outputs so that the user can quickly connect and measure electrical characteristics and waveforms. The Evaluation Board schematic diagram is shown in Figure 1. The SP7616 driver provides a simple solution for a matched current source for any color LED. The current in the LEDs is programmed by an external resistor. The SP7616 is capable of driving up to four LED chains from a source of up to 30Vin. The evaluation board contains one SP7616 driver, and four locations to solder the led chains for ease of use. The user will need to supply an active high PWM signal or an external power supply with at least 2.5V volts to turn the Sp7616 driver on. (Note R2 on the PCB is referred to as Rset in the data sheet.)
R2=46K
Figure 1. Evaluation Board Schematic Diagram for SP7616
Rev 07/28/06
SP7616 Evaluation Board Manual
Copyright 2006 Sipex Corporation
USING THE EVALUATION BOARD
1) Vin requirements and PWM pin The user of the SP7616 will need to supply Vin and an PWM signal that is active high. The PWM pin signal is a logic level signal and should range between 0 an 5V. The threshold is 2.4V for a logic high. 2) Setting the LED current The LED current is set through the Iset resistor. The SP7616 provides an internal reference voltage that is set to 1V at the ISETPin (Pin3). RSET is then determined by using equation 1. R2 = VISET*IMULT/ILED (k), Where VISET is the internal reference (1V) IMULT Current Multiplication Ratio ILED is the desired Led current. (1)
In example 1: For a 20mA LED current, the current set resistor should be R2=1V*920/20mA (k), R2=46K 3) LED dimming PWM dimming The LED dimming control is done through the PWM pin. The acceptable frequency range of this signal is 100Hz to 5 kHz. The acceptable duty cycle range of the signal is 10% to 90% at 1KHZ. When the PWM pin is driven low, only the LED current sources are disabled while the rest of the chip is still enabled. . Analog dimming control Besides digital PWM control, the LED current can be controlled continuously (from high to low LED current) by raising the voltage at the bottom of RSET from 0V to 1V maximum. RSET value may be determined from equation 1. Equation 2 shows the effect of using a VMOD in the circuit on the Led current ILED = (1V - VMOD)*IMULT/RSET mA (2) Where 1V typical ISET pin voltage IMULT Current Multiplication Ratio ILED is the desired Led current. VMOD is the adjustment voltage VMOD is an adjustment voltage applied to the bottom side of R2, 920 is a typical current multiplication ratio IMULT, and ILED is a required LED current in mA/channel. Figure 2 shows the location of the external VMOD source.
2
R2=46K
Figure 2
4) EVALUATION BOARD LAYOUT
Figure 4. SP7616 Evaluation Board Layout top side (not an actual size)
Bottom Side PCB
Figure 5. SP7616 Evaluation Board Layout bottom side (not an actual size) Table 2. SP761X_EB List of Materials Count 1 1 1 3 Reference Designator U1 C1 R2 (RSET) GND VIN PWM Value 1uF 46K Part Number SP7616 GRM21BR71H105KA12L CRCW06034602J K24C/M Manufacturer SP7616 Murata Vishay Vector Electronic Comments
1uF 50V capacitor 805 size Post for Vin PWM signal and GND
3
ORDERING INFORMATION Model Temperature Range Package Type
SP7616_EB......................... -40C to +85C.................................................................. SP7616 Evaluation Board
4

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