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BD8355MWV Datasheet(PDF) 8 Page - Rohm |
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BD8355MWV Datasheet(HTML) 8 Page - Rohm |
8 / 21 page Technical Note 8/20 BD8355MWV www.rohm.com 2011.12 - Rev.A © 2011 ROHM Co., Ltd. All rights reserved. ● Functional Description / peripheral devices setting 1. Internal Regulator (VREGA, VREGD) Both VREGA and VREGD are internal regulator of 3.6 V output. Bypass VREGA/VREGD to GND with a capacitor be- tween 0.47 µF and 2.2 µF. In addition, it needs care for the voltage between VREGA and VREGD not to excess 0.3 V to avoid IC malfunctions. 2. Control block (SHUT DOWN) Inputting voltages to CTL14, 2, 35, 6, and 7 control ON/OFF of respective channels. Note that it is impossible to inde- pendently control CH1 and 4, and to independently control CH3 and 5. In addition, turn on any CTL1-6 and wait 500 usec before turning on CTL7. Input higher voltage than 2 V to CTL14, 2, 35, or 6 to turn on each channel. Open or in- put voltage -0.3 ~ 0.4 V to those to turn off. Input 2 ~ 5.5 V to CTL7 to turn on CH7. Open or input voltage -0.3 ~ 0.4 V to CTL7 to turn off. The states of output terminals (Lx1-7), FB terminals, SCP/SCP6 terminals, and internal regulator (VREGA and VREGD) are written below. Each CTL terminal contains pull down resistor of 1MΩ (typ.) 14 2 35 67123 456712 34567 LLL LLLLL LLL H-Z LL LLLLLL LLL HL L L L A L L A L L H-Z A L L A LLL A A A L L H L LLL A L LLL H-Z L A LLLLL A A A L LL H LLLL A L A L H-Z L L AL AL L A A A L LLL H LLLL LL A H-Z LL LLL A L A A L A L* L* L* L* H L* L* L* L* L* L* A L* L* L* L* L* L* AAAA L* H H H H H A AAAAAA AAAAAA AAAAA A: active SCP6 * Turn on any CTL1-6 before turn on CTL7. Conditions of Lx1 ~ 6, FB1 ~ 6, SCP6 are changed with active channel. CTL Lx FB VREGA VREGD SCP 3. Output voltage/current setting Fig. 7 Setting of feedback resistance (a) Setting output voltage of CH1-6 The reference voltages of ERROR AMP. are 0.8 V (CH1) and 1 V (CH2-6). The output voltages are determined as equation (1) and (2). Set the value of feedback resistance R1 and R2 which are connected to INV1-6 pin. (b) Setting output current of CH7 The reference voltage of CH7 ERROR AMP. is 0.3 V. The current flowing LED is determined as equation (3). Set the value of feedback resistance R3, considering the tolerance current of LED. 4. Startup/Stop sequence To avoid rush current on startup, each channel has soft start function. The output voltage of CH1 reaches to the target in Tss1=2.5msec (typ.) and the output voltage of CH2 ~ 6 reaches to the target in Tss2-6=3.1msec (typ.). In case of CH7, the output of error amplifier is restricted in TDTC7=15msec (typ.). Note that Tss1-6, TDTC7 vary from typical value Ttyp as following with setting of switching frequency. 5. Protection matrix The following table displays state of outputs when protection is operating. Lx1-5 Lx6 Lx7 FB1-6 FB7 VREGA VREGD HVREG SCP SCP6 Short Circuit Protection (CH1-5,7) H-Z A H-Z A A A A A - A Short Circuit Protection (CH6) A H-Z A A A A A A A - Under Voltage Lockout (VCC) H-Z H-Z H-Z NA NA A A NA NA NA Under Voltage Lockout (VREGA) H-Z H-Z H-Z NA NA - A NA NA NA Under Voltage Lockout (VREGD) H-Z H-Z H-Z NA NA A - NA NA NA Under Voltage Lockout (HVREG) H-Z H-Z A NA A A A - NA NA Thermal Shutdown (TSD) H-Z H-Z H-Z NANA NANANANANA A: active NA: non-active |
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