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℃, V
IN
=5.6V)
Parameter
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
EN terminal H threshold voltage
EN terminal L threshold voltage
SS/DELAY terminal source current
Current capability should not exceed Pd.
Symbol
I
Q_active
I
Q_stby
V
REF
V
OVP
V
LVP
I
PDET
f
OSC
R
PFET
R
NFET
V
UVLO
I
LSW
V
ENH
V
ENL
I
SSSO
Specification value
MIN
-
-
0.792
30
-90
1
500
-
-
3.8
-
2.0
-
2
TYP
1.3
350
0.8
60
-60
-
550
170
130
4.0
0
-
-
4
MAX
2.0
700
0.808
90
-30
-
600
240
200
4.2
1
-
0.5
6
UNIT
mA
μA
V
mV
mV
mA
kHz
mΩ
mΩ
V
μA
V
V
μA
Condition
V
FB
= 0.83V, V
FC
= 1V
V
EN
= 0V
Monitoring FB terminal
Monitoring FB terminal
V
PDET
< 0.5V
R
OSC
= 220kΩ
I
SW
= 1A
I
SW
= -1A
V
EN
= 0V, V
IN
= 6V
V
FB
:FB terminal voltage, V
EN
:EN terminal voltage, V
FC
:FC terminal voltage, V
PDET
: PDET terminal voltage
Permissible loss
Permissible loss ： PD [W]
Fig. 1 heat decrease curve
2 / 11
●
Block Diagram
Fig.2 Block diagram
●
Pin description
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
Symbol
SGND
FB
PDET
SW
PGND
PGND
SW
SW
VIN
VIN
VIN
REG
EN
FC
RT
Internal regulator
Enable input
Error amplifier output
Frequency adjustment resistance connection terminal
Internal regulator
ON/OFF control for device operation
The soft start time is adjusted with the connected capacitor
Error amplifier phase compensation point
The switching frequency is set by the connected resistance
Power supply input terminal
Power supply input. The decoupling is done to PGND
Signal GND terminal
Feed back terminal
Off latch signal output
Output terminal
Power GND terminal
Output terminal
Description
Explanation
Small signal system GND
Output voltage detection
Reset output
Switching output
GND for power MOSFET
Power Mos output
SS/DELAY
Soft start adjustment capacity connection terminal
3 / 11
●
Pin equivalence circuit diagram
No.
Symbol
1
SGND
Explanation
GND (connected 0V)
Terminal equivalent circuit diagram
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
4 / 11
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