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System Power Supply for TV Series Built-in 1ch FET Synchronous Rectification Type DC/DC converters BD8629FS
- Description BD8629FS has realized the high performance and reliability required as a power supply for thin-screen TV. With built-in FET 1ch current mode control, the DC/DC Converter series has the advantage of high-speed load response and wide phase margin. Due to the high-speed load response, it is most suitable for TV-purpose processors with increasingly high performance, and due to the wide phase margin it leaves a good margin for board pattern & constant setting and so facilitates its application design. As a high-reliability design, it has various built-in protection circuits (overcurrent protection, output voltage abnormal protection, thermal protection, and off-latch function at the time of abnormality etc.), therefore as an advantage it does not easily damage in every possible abnormal condition such as all-pin short circuit test etc. and hence most suitable for thin-screen TV which requires the high reliability.
- Features 1) High efficiency in all load area 2) 2.0A output current 3) Low RDS(ON) internal switches (PchMOS:170mΩ, NchMOS:130mΩ) 4) ±1% reference voltage accuracy 5) Programmable frequency : 250kHz-1MHz 6) Terminal RT OPEN/SHORT detecting function 7) Over current protection function 8) Output over voltage/low voltage protection function (over : FB > VREF +60mV , low : FB < VREF -60mV) 9) Timer off latch function in abnormal circumstances 10) Thermal shutdown function 11) Under voltage protection 12) Soft start/start delay circuit 13) Soft start time out function 14) SSOP-A16 package Aug. 2008
- Electrical characteristic (Unless otherwise noted Ta=25 ℃, VIN=5.6V) Parameter Symbol Specification value UNIT Condition MIN TYP MAX VIN supply current (operating) I Q_active - 1.3 2.0 mA V FB = 0.83V, VFC = 1V VIN supply current (standby) I Q_stby - 350 700 μA V EN = 0V Reference voltage (VREF) V REF 0.792 0.8 0.808 V Output rise detection voltage V OVP 30 60 90 mV Monitoring FB terminal Output decrease detection voltage V LVP -90 -60 -30 mV Monitoring FB terminal Terminal PDET output current I PDET 1 - - mA V PDET< 0.5V Oscillation frequency f OSC 500 550 600 kHz R OSC = 220kΩ Pch FET ON resistance R PFET - 170 240 m Ω I SW = 1A Nch FET ON resistance R NFET - 130 200 m Ω I SW = -1A UVLO voltage V UVLO 3.8 4.0 4.2 V SW leak current I LSW - 0 1 μA V EN= 0V, VIN = 6V EN terminal H threshold voltage V ENH 2.0 - - V EN terminal L threshold voltage V ENL - - 0.5 V SS/DELAY terminal source current I SSSO 2 4 6 μA VFB :FB terminal voltage, VEN :EN terminal voltage, VFC :FC terminal voltage, VPDET: PDET terminal voltage Current capability should not exceed Pd. Permissible loss Permissible loss ： PD [W] Fig. 1 heat decrease curve
- Block Diagram Fig.2 Block diagram
- Pin description No. Symbol Description Explanation
1 SGND Signal GND terminal Small signal system GND
2 FB Feed back terminal Output voltage detection
3 PDET Off latch signal output Reset output
4 SW Output terminal Switching output
5 PGND Power GND terminal GND for power MOSFET
6 PGND
7 SW Output terminal Power Mos output
9 VIN
Power supply input terminal Power supply input. The decoupling is done to PGND 10 VIN
11 VIN
12 REG Internal regulator Internal regulator
13 EN Enable input ON/OFF control for device operation
14 SS/DELAY Soft start adjustment capacity connection terminal The soft start time is adjusted with the connected capacitor
15 FC Error amplifier output Error amplifier phase compensation point
16 RT Frequency adjustment resistance connection terminal The switching frequency is set by the connected resistance
- Pin equivalence circuit diagram No. Symbol Explanation Terminal equivalent circuit diagram
1 SGND GND (connected 0V)
2 FB Output voltage detection terminal
3 PDET Off latch signal output terminal
4,7,8 SW Output terminal 5,6 PGND Power GND (Same voltage as SGND) 9,10,11 VIN Power supply input terminal
No. Symbol Explanation Terminal equivalent circuit diagram
12 REG Internal regulator output terminal
13 EN Enable terminal
No. Symbol Explanation Terminal equivalent circuit diagram
14 SS Soft start time adjustment
15 FC Error amplifier compensation
16 RT Oscillator frequency adjustment
- ● Operation description Enable control The device can be controlled ON/OFF by EN terminal (13 pin) voltage. An internal circuit starts when VEN reaches 1.4V. Fig. 3 ON/OFF transition wave form in EN controlling Soft start time set function As for BD8629FS, output can do soft start without overshoot by charging soft start capacity (CSS) connected between SS and SGND terminal. Also, soft start time (tss) can be set by setting soft start capacity (CSS) arbitrarily.
OSC oscillation frequency setting function The output oscillation frequency can be set by connecting resistance between terminal RT (16 pins) and SGND (range = 250kHz - 1MHz) The relation between RT terminal resistance and the oscillation frequency follows Fig.3. 100 1000 10000 10 100 1000 10000 RT端子抵抗[kΩ] スイッチング周波数[kHz] Fig. 4 RT resistance-oscillation frequency RT terminal resistance [kΩ] Frequency [kHz]
- ● Protection function Protection circuit is effective for destruction prevention due to accident so that avoid using under continuous protection operation. Low voltage protection function (LVP) The voltage of the terminal FB (2 pins) is compared with internal reference voltage VREF. If FB terminal voltage falls below VLVP(= VREF -60mV) and the state continues for 500us, output changes to low voltage and the state is fixed. In that case , PDET (3pin) output changes to L. Table 4-1 output low voltage protection function EN terminal SS terminal FB terminal Low voltage protection function Low voltage protection operation >VIHEN >1.4V(typ) <VLVP Effective ON >VLVP OFF <1.4V(typ) - Invalidity OFF <VILEN - - Invalidity OFF ＊ Low voltage protection function is available when SS terminal voltage becomes more than 1.4V (typ) in the transition to ON control (during soft start). Over voltage protection function(OVP) The voltage of the terminal FB is compared with internal reference voltage VREF. If FB terminal voltage is over Vovp (=VREF +60mV) and the state is continues for 500usec, output changes to low voltage and the state is fixed. Table 4-2 output overvoltage protection function EN terminal SS terminal FB terminal Over voltage protection function Over voltage protection operation >VIHEN >1.4V(typ) >VOVP Effective ON <VOVP OFF <1.4V(typ) - Invalidity OFF <VILEN - - Invalidity OFF ＊ Over voltage protection function is available when SS terminal voltage becomes more than 1.4V (typ) in the transition to ON control (during soft start). FB terminal voltage VREF ON OFF Protection OVP LVP VREF＋60ｍV VFB PDET terminal HIGH LOW VREF-60ｍV 500[us] 500[us] Fig. 5 Output voltage error detection range
Under voltage lock out protection (UVLO) As for BD8629FS, the power-supply voltage decrease detection protection circuit is built in. It the input voltage decrease below the UVLO voltage (4.0V typ), the device state changes to the standby mode (Moreover, to prevent the chattering of the output) hysteresis width of 300mV(typ) has been installed in the UVLO cancel voltage. RT terminal open/short protection function (RTO/RTS) RT terminal opening/short protection function prevent the clock from abnormal oscillation. If RT terminal open/short protection function is detect ed, output voltage changes to low level and is fixed. Terminal RT opening/short protection function is al ways effective after the power supply start-up. Terminal RT opening/short protection function is av ailable if the state cont inue for 500usec, abnormal detection operates when the state continues about 500 μsec(typ). Soft start time-out function If VSS doesn't exceed VSSTH within 64msec (typ) since a soft start began, BD8629FS controls an off latch. Vo is fixed in a low level. Fig. 6 Soft start time-out Error detection (off latch) release method BD8629FS enters the state of an off latch when the protection function operates. To release the off latch state, EN terminal voltage should be changed to low level once time. Thermal shut down function Thermal shut down circuit (TSD circuit) is built into BD8629FS. When the temperature of the chip exceeds Tjmax=175, the DC/DC converter is fixed in a low voltage. TSD function is aimed to shut down IC from thermal reckless driving under an abnormal state to exceed Tjmax=175. It aims at neither protection nor the guarantee of the set. Therefore, please do not use this function to protect the set. Over current protection function The over current protection function has been achieved by limiting the current that flows on high side MOSFET. The current is controlled in every one cycle of the switching frequency. When an abnormal state continues for about 500μsec(typ), the output is fixed in a low level.
Catalog No.08T271A '08.8 ROHM © Tape Quantity Direction of feed Embossed carrier tape 2500pcs (The direction is the 1pin of product is at the upper left when you hold reel on the left hand and you pull out the tape on the right hand) <Tape and Reel information> （Unit:mm) SSOP-A16 <Dimension> 6.6±0.2 4.4±0.2 6.2±0.3 0.11 1.5±0.1 0.36±0.1 0.3Min. 0.8 0.15±0.1 0.1 ※When you order , please order in times the amount of package quantity. Reel 1pin 1234 1234 1234 Direction of feed 1234 1234 1234 1234 1234
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