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BD3531F Datasheet(PDF) 2 Page - Rohm |
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BD3531F Datasheet(HTML) 2 Page - Rohm |
2 / 19 page BD3531F 2/15 © 2015 ROHM Co., Ltd. All rights reserved. www.rohm.com TSZ22111・15・001 TSZ02201-0J2J0A900950-1-2 02.Nov.2015 Rev.001 Pin Configuration Pin Descriptions Description of Blocks 1. VCC The VCC pin is for the independent power supply input that operates the internal circuit of the IC. It is the voltage at this pin that drives the IC’s amplifier circuits. The VCC input ranges 5V and maximum current consumption is 4mA. A bypass capacitor of 10 μF or so should be connected to this pin when using the IC in an application circuit. 2. VDDQ This is th e power supply input pin for an internal voltage divider network. The voltage at VDDQ is halved by two 50kΩ internal voltage-divider resistors and the resulting voltage serves as reference for the VTT output. Since VTT = 1/2VDDQ, the JEDEC requirement for DDR-SDRAM can be satisfied by supplying the correct voltage to VDDQ. Noise input should be avoided at the VDDQ pin as it is also included by the voltage-divider at the output. An RC filter consisting of a resistor and a capacitor (220Ω and 2.2μF, for instance,) may be used to reduce the noise input but make sure that it will not significantly affect the voltage- divider’s output. 3. VTT_IN VTT_IN is the power supply input pin for the VTT output. Input voltage may range from 1.0V to 5.5V, but consideration must be given to the current limit dictated by the ON-Resistance of the IC and to the change in allowable loss due to input/output voltage difference. Generally, the following voltages are supplied: ・ DDR I VVTT_IN =2.5V ・ DDRII VVTT_IN =1.8V Take note that a high-impedance voltage input at VTT_IN may result in oscillation or degradation in ripple rejection, so connecting a 100 μF capacitor with minimal change in capacitance to VTT_IN terminal is recommended. However, this impedance may depend on the characteristics of the power supply input and the impedance of the PC board wiring, which must be carefully checked before use. 4. VREF BD3531F provides a constant voltage, VREF, which is independent from the VTT output and can serve as reference input for memory c ontrollers and DRAMs. The voltage level of VREF is kept constant even if the EN pin is at “Low” level, making the use of this IC compatible with the “Self Refresh” state of DRAMs. In order to stabilize the output voltage, connecting the correct combination of capacitor and resistor to VREF is necessary. For this purpose, a combination of 1.0μF to 2.2μF ceramic capacitor, characterized by minimal variation in capacitance, and a 0.5Ω to 2.2Ω phase compensating resistor is recommended. 5. VTTS VTTS is a sense pin for the load regulation of the VTT output voltage. In case the wire connecting VTT pin and the load is too long, connecting VTTS pin to the part of the wire nearer to the load may improve load regulation. Pin No. Pin Name Pin Function 1 GND GND Pin 2 EN Enable Input Pin 3 VTTS Detector Pin for Termination Voltage 4 VREF Reference Voltage Output Pin 5 VDDQ Reference Voltage Input Pin 6 VCC VCC Pin 7 VTT_IN Termination Input Pin 8 VTT Termination Output Pin VTT_IN GND EN VTTS VREF VTT VCC VDDQ 1 2 3 4 5 6 7 8 TOP VIEW |
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