BD8629FS [ROHM]
Built-in 1ch FET Synchronous Rectification Type DC/DC converters; 内置1通道FET同步整流型DC / DC转换器
| 型号： | BD8629FS |
| 厂家： | 
ROHM |
| 描述： | Built-in 1ch FET Synchronous Rectification Type DC/DC converters |
| 文件： | 总12页 (文件大小：607K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
TECHNICAL NOTE
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)
Specification value
TYP
Parameter
Symbol
UNIT
Condition
MIN
MAX
VIN supply current (operating)
VIN supply current (standby)
Reference voltage (VREF)
Output rise detection voltage
Output decrease detection voltage
Terminal PDET output current
Oscillation frequency
Pch FET ON resistance
Nch FET ON resistance
UVLO voltage
SW leak current
IQ_active
IQ_stby
VREF
VOVP
VLVP
IPDET
fOSC
RPFET
RNFET
VUVLO
ILSW
-
1.3
350
0.8
60
-60
-
2.0
700
0.808
90
-30
-
mA
μA
V
mV
mV
mA
kHz
mΩ
mΩ
V
VFB = 0.83V, VFC = 1V
VEN = 0V
-
0.792
30
-90
1
Monitoring FB terminal
Monitoring FB terminal
VPDET< 0.5V
500
-
-
3.8
-
2.0
-
550
170
130
4.0
0
-
-
4
600
240
200
4.2
1
-
0.5
6
ROSC = 220kΩ
ISW = 1A
ISW = -1A
μA
V
V
VEN= 0V, VIN = 6V
EN terminal H threshold voltage
EN terminal L threshold voltage
SS/DELAY terminal source current
VENH
VENL
ISSSO
2
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
Fig. 1 heat decrease curve
2 / 11
● Block Diagram
Fig.2 Block diagram
● Pin description
Description
Explanation
No.
1
Symbol
SGND
FB
Small signal system GND
Signal GND terminal
Feed back terminal
Output voltage detection
Reset output
2
3
Off latch signal output
Output terminal
PDET
SW
Switching output
4
5
PGND
PGND
SW
GND for power MOSFET
Power Mos output
Power GND terminal
Output terminal
6
7
8
SW
9
VIN
Power supply input. The decoupling is done to PGND
10
11
12
13
14
15
16
Power supply input terminal
VIN
VIN
Internal regulator
Internal regulator
REG
EN
ON/OFF control for device operation
Enable input
The soft start time is adjusted with the connected capacitor
Error amplifier phase compensation point
The switching frequency is set by the connected resistance
Soft start adjustment capacity connection terminal
Error amplifier output
SS/DELAY
FC
Frequency adjustment resistance connection terminal
RT
3 / 11
●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
Power GND
(Same voltage as SGND)
5,6
PGND
VIN
9,10,11
Power supply input terminal
4 / 11
No.
Symbol
Explanation
Terminal equivalent circuit diagram
12
REG
Internal regulator output terminal
13
EN
Enable terminal
5 / 11
No.
Symbol
Explanation
Terminal equivalent circuit diagram
Soft start time adjustment
terminal
14
SS
Error amplifier compensation
terminal
15
FC
Oscillator frequency adjustment
terminal
16
RT
6 / 11
● 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.
7 / 11
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.
10000
1000
100
10
10
100
1000
10000
RT terminal resistance [kΩ]
Fig. 4 RT resistance-oscillation frequency
8 / 11
● 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
Low voltage
protection function
Low voltage
protection operation
EN terminal
>VIHEN
SS terminal
>1.4V(typ)
FB terminal
<VLVP
ON
OFF
OFF
OFF
Effective
>VLVP
<1.4V(typ)
-
-
-
Invalidity
Invalidity
<VILEN
＊ 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
Over voltage
protection function
Over voltage
protection operation
EN terminal
>VIHEN
SS terminal
>1.4V(typ)
FB terminal
>VOVP
ON
OFF
OFF
OFF
Effective
<VOVP
<1.4V(typ)
-
-
-
Invalidity
Invalidity
<VILEN
＊ 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).
VFB
VREF＋60ｍV
FB terminal voltage
VREF
VREF-60ｍV
0
ON
Protection
500[us]
OVP
500[us]
LVP
OFF
HIGH
LOW
PDET terminal
Fig. 5 Output voltage error detection range
9 / 11
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 detected, output voltage changes to low level and is fixed.
Terminal RT opening/short protection function is always effective after the power supply start-up.
Terminal RT opening/short protection function is available if the state continue for 500usec, abnormal
detection operates when the state continues about 500μsec(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.
10 / 11
SSOP-A16
<Dimension>
<Tape and Reel information>
Tape
Embossed carrier tape
2500pcs
Quantity
6.6 0.2
Direction
of feed
E2
16
9
(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)
1
8
0.15 0.1
0.1
0.8
0.36 0.1
Direction of feed
1pin
Reel
※When you order , please order in times the amount of package quantity.
（Unit:mm)
Catalog No.08T271A '08.8 ROHM ©
Appendix
Notes
No technical content pages of this document may be reproduced in any form or transmitted by any
means without prior permission of ROHM CO.,LTD.
The contents described herein are subject to change without notice. The specifications for the
product described in this document are for reference only. Upon actual use, therefore, please request
that specifications to be separately delivered.
Application circuit diagrams and circuit constants contained herein are shown as examples of standard
use and operation. Please pay careful attention to the peripheral conditions when designing circuits
and deciding upon circuit constants in the set.
Any data, including, but not limited to application circuit diagrams information, described herein
are intended only as illustrations of such devices and not as the specifications for such devices. ROHM
CO.,LTD. disclaims any warranty that any use of such devices shall be free from infringement of any
third party's intellectual property rights or other proprietary rights, and further, assumes no liability of
whatsoever nature in the event of any such infringement, or arising from or connected with or related
to the use of such devices.
Upon the sale of any such devices, other than for buyer's right to use such devices itself, resell or
otherwise dispose of the same, no express or implied right or license to practice or commercially
exploit any intellectual property rights or other proprietary rights owned or controlled by
ROHM CO., LTD. is granted to any such buyer.
Products listed in this document are no antiradiation design.
The products listed in this document are designed to be used with ordinary electronic equipment or devices
(such as audio visual equipment, office-automation equipment, communications devices, electrical
appliances and electronic toys).
Should you intend to use these products with equipment or devices which require an extremely high level
of reliability and the malfunction of which would directly endanger human life (such as medical
instruments, transportation equipment, aerospace machinery, nuclear-reactor controllers, fuel controllers
and other safety devices), please be sure to consult with our sales representative in advance.
It is our top priority to supply products with the utmost quality and reliability. However, there is always a chance
of failure due to unexpected factors. Therefore, please take into account the derating characteristics and allow
for sufficient safety features, such as extra margin, anti-flammability, and fail-safe measures when designing in
order to prevent possible accidents that may result in bodily harm or fire caused by component failure. ROHM
cannot be held responsible for any damages arising from the use of the products under conditions out of the
range of the specifications or due to non-compliance with the NOTES specified in this catalog.
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Appendix1-Rev2.0
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