Preliminary FT838MBD/838MDD
Fremont Micro Devices
High Efficiency Off-Line CC/CV Switch
DESCRIPTION
FEATURES
Constant-Current (CC) and
The FT838MBD/FT838MDD controller device is
Constant-Voltage (CV) with Primary Side
optimized for high-performance, low power
Control
switching mode power supply applications. The
Proprietary technology enabling high
FT838MBD/FT838MDD
efficiency and fast dynamic response
charger design by eliminating an opto-coupler
No audible noise over entire operating
and TL431. Its highly integrated functions such
range
as Under Voltage Lockout (UVLO), Leading
Built-in power MOS
Edge
Built-in Cable Compensation
compensation offer the users a high efficiency
Built-in Line Compensation
and
Primary-side feedback eliminates
applications.
Blanking
low
cost
(LEB)
solution
facilitates
and
for
built-in
AC/DC
CC/CV
cable
power
opto-coupler and TL431
Cycle-by-Cycle Current Limiting
Power
Over Temperature Protection
FT838MBD/FT838MDD can achieve both high
VCC Over Voltage Protection
average efficiency
CV Open-loop Protection
and super low standby power.
supplies
built
with
fast dynamic load response
Excellent capacitive loading start-up
Furthermore, FT838MBD/FT838MDD features
performance
fruitful protections like Open Circuit Protection
and Over Temperature Protection to eliminate
the external protection circuits and provide
TYPICAL APPLICATION
reliable operations. FT838MBD/FT838MDD is
Adapter/Charger for Cell/Cordless Phones,
available in DIP8 package.
PDAs, MP3 and Other Portable Apparatus
Standby and Auxiliary Power Supplies
Set Top Boxes (STB)
Adapter for ADSL / WiFi Wireless
AC/DC LED Driver applications
© 2013 Fremont Micro Devices Inc.
Confidential Rev0.80
DS838MBD/MDD-A0-Page1
Fremont Micro Devices
Preliminary FT838MBD/838MDD
TYPICAL APPLICATION CIRCUIT
Figure 1: FT838MBD/838MDD Typical Application Circuit
© 2013 Fremont Micro Devices Inc.
Confidential Rev0.80
DS838MBD/MDD-A0-Page2
Fremont Micro Devices
Preliminary FT838MBD/838MDD
ABSOLUTE MAXIMUM RATINGS
FB to GND
...
.
.
.
.... -0.3V to +7V
CS to GND
...
.
.....-0.3V to +7V
VCC to GND
..
.
-0.3V to +30V
C to GND
...
.
.
......-0.3V to +700V
Operating Temperature Range
...
...-40
to +125
Junction Temperature
..
.... -40
to +150
Storage Temperature Range
..
.-60
to +150
ESD Protection HBM
.....
.2000V
ESD Protection MM
..
.200V
*Stresses exceeding Maximum Ratings may damage the device. Maximum Ratings are stress
ratings only. Functional operation above the Recommended Operating Conditions is not
implied. Extended exposure to stresses above the Recommended Operating Conditions may
affect device reliability.
© 2013 Fremont Micro Devices Inc.
Confidential Rev0.80
DS838MBD/MDD-A0-Page3
Preliminary FT838MBD/838MDD
Fremont Micro Devices
PIN CONFIGURATION
Figure 2: Pin Assignments
TERMINAL DEFINITION
Pin
Name
1
CS
Primary current sense
2
FB
Output voltage feedback pin
3
GND
Ground.
4
VCC
Supply voltage
NC
No connection
5
6
7
8
D
Description
The drain of the power MOS. This pin is connected to the primary lead of the
transformer
Table 1
© 2013 Fremont Micro Devices Inc.
Confidential Rev0.80
DS838MBD/MDD-A0-Page4
Preliminary FT838MBD/838MDD
Fremont Micro Devices
ORDERING INFORMATION
FT838MxD x D - xx
Circuit Type
HSF and Packaging
B or D
RB: RoHS and Tube
RT: RoHS and T&R
Cable Comp
GB: Green and Tube
0: 0%
GT: Green and T&R
1: 3%
Package
2: 6%
DIP8
3: 9%
FT838MBD /FT838MDD
Device
DESIGNATOR
SYMBOL
Options
0
Cable Comp = 0%
FT838MBD
1
Cable Comp = 3%
FT838MDD
2
Cable Comp = 6%
3
Cable Comp = 9%
Table 2
MARKING RULE
Figure 3: Marking Rule
: Represents Version (0, 1, 2 or 3)
: for internal reference
© 2013 Fremont Micro Devices Inc.
Confidential Rev0.80
DS838MBD/MDD-A0-Page5
Fremont Micro Devices
Preliminary FT838MBD/838MDD
Block Diagram
Figure 4: FT838MBD/838MDD Block Diagram
© 2013 Fremont Micro Devices Inc.
Confidential Rev0.80
DS838MBD/MDD-A0-Page6
Preliminary FT838MBD/838MDD
Fremont Micro Devices
ELECTRICAL CHARACTERISTICS
(For typical values Tj=25
, Vcc=12V, unless otherwise noted)
Characteristic
Symbol
Min
Typ
Max
Unit
Vcs_max
535
552
575
mV
Tleb
350
400
450
ns
200
ns
2.944
V
Current Sense
Maximum Current Threshold
Leading Edge Blanking Duration
Propagation Delay
Tpd
(OUT=1.0nF to GND)
Feedback Section
Feedback Voltage Threshold
Vfb
CCM protection Threshold Level
Vcp
2.856
2.9
100
mV
Supply Section
Start Up Threshold Voltage
Vcc_on
15.5
16.2
17.5
V
Under Voltage Lockout Voltage
Vcc_off
5.2
5.5
6.0
V
VCC Start Up Current
Istart_up
2
5
uA
Operating Current
Iop
0.4
0.5
0.7
mA
Feedback Loop Open Protection
Ifb_open
90
115
140
uA
VCC Over Voltage Protection
Vcc_OVP
26
27
28
V
Over Temperature Protection
T_OTP
40
mV
Protection Section
145
Compensation
Line Compensation (Ifb=1mA)
Vline
25
0
Cable
1
compensation
2
33
0
3
Kcab
%
6
3
9
Power MOS Section (FT838MBD)
Characteristic
Static drain-source
on-resistance
Drain-source
breakdown voltage
Drain-source
leakage current
Maximum Drain
Current
Symbol
RDS_ON
BVDSS
IDSS
IDMAX
Test
condition
Min
VGS=10V,
IDS=250uA
650
Unit
V
VGS=0V,
10
VDS=650V
Vd=4V
Max
5.5
IDS=0.5A
VGS=0V,
Typ
0.6
0.7
uA
A
Power MOS Section (FT838MDD)
Static drain-source
on-resistance
Drain-source
RDS_ON
BVDSS
© 2013 Fremont Micro Devices Inc.
VGS=10V,
2.6
IDS=0.5A
VGS=0V,
650
Confidential Rev0.80
V
DS838MBD/MDD-A0-Page7
Fremont Micro Devices
breakdown voltage
Drain-source
leakage current
Maximum Drain
Current
Preliminary FT838MBD/838MDD
IDS=250uA
IDSS
IDMAX
VGS=0V,
10
VDS=650V
Vd=3V
1.0
1.1
uA
A
Table 3
© 2013 Fremont Micro Devices Inc.
Confidential Rev0.80
DS838MBD/MDD-A0-Page8
Fremont Micro Devices
Preliminary FT838MBD/838MDD
FUNCTIONAL DESCRIPTION
Operating Description
FT838MBD/FT838MDD is a cost effective and high-performance AC-DC power supply controller for
off-line low power AC-DC applications including battery chargers, adaptors and LED lighting. The
constant voltage (CV) and constant current (CC) control are achieved accurately without the secondary
feedback circuit.
Start up Control
Start-up current of FT838MBD/838MDD is very low so that a start-up resistor with high resistance and
low-wattage is allowed to supply the start-up power for the controller. The large value startup resistor
minimizes the power loss in operations and allows quick start up. With a special fast startup technology,
FT838MBD/FT838MDD starts up easily in capacitive loading applications.
Operating current
The operating current of FT838MBD/FT838MDD is as low as 500uA. Good efficiency is achieved with
the low operating current. Low operating current also reduces the Vcc hold-up capacitance
requirement.
Constant voltage (CV) and constant current (CC) Operation
The FT838MBD/FT838MDD can accurately achieve CV/CC characteristic output without secondary
side voltage and current-feedback circuits. It operates in CV mode to regulate the output voltage by
capturing the auxiliary winding feedback voltage at FB pin. The auxiliary winding feedback voltage is
proportional to secondary winding, so it provides controller the feedback signal from secondary side
and achieves constant-voltage output. In CC mode, the controller detects the secondary discharger
peak current and the discharger time, which determines the off-time of the base driver to make the
output average current constant.
Primary peak current modulation
Primary peak current is constant at constant current mode. And primary peak current is modulated at
constant voltage mode for the purposes of good dynamic load response and no audible noise over
entire operating range. According to the output loading current the current threshold voltage is
modulated from 0.55V to 0.27V. The current threshold voltage is 0.55V at rated load and 0.27V at light
load.
Leading edge blanking
Each time the power MOS transistor is switched on, a turn-on spike occurs at the sense resistor. To
avoid premature termination of the switching pulse, a 400ns leading edge blanking time is built in.
Conventional RC filtering can therefore be omitted. During this blanking period, the current limit
comparator is disabling and cannot switch off the base driver.
Under voltage lockout (UVLO)
FT838MBD/FT838MDD turn-on Vcc_on and turn-off Vcc_off are 16.2 V and 5.5 V, respectively. During
start-up, the hold-up capacitor must be charged to 16.2V through the start-up resistor. The hold-up
© 2013 Fremont Micro Devices Inc.
Confidential Rev0.80
DS838MBD/MDD-A0-Page9
Fremont Micro Devices
Preliminary FT838MBD/838MDD
capacitor continues to supply Vcc until power can be delivered from the auxiliary winding of the
transformer. Vcc must not drop below 5.5 V during this start-up process. This UVLO hysteresis window
ensures that hold-up capacitor is sufficient to supply Vcc during start-up.
Protection control
With rich protection features of FT838MBD/FT838MDD, excellent power supply system reliability can
be achieved. The protection features include cycle by cycle current limiting, Vcc over voltage protection
and clamp, over temperature protection, feedback loop open circuit protection and Vcc under voltage
lockout, etc.
Integrated MOS
Power MOS is integrated in FT838MBD/FT838MDD for low cost and/or space limited applications,
respectively.
Output cable compensation
The output cable compensation provides a constant output voltage at the end of the cable over the
entire load range in constant voltage mode. As the converter load increases from no-load to the peak
current load, the voltage drop introduced across the output cable is compensated by increasing the
feedback pin reference voltage.
© 2013 Fremont Micro Devices Inc.
Confidential Rev0.80
DS838MBD/MDD-A0-Page10
Preliminary FT838MBD/838MDD
Fremont Micro Devices
PACKAGE INFORMATION
DIP8 Package
Symbol
Dimensions In Millimeters
Min
Max
4.310
Dimensions In Inches
Min
Max
0.146
0.170
A
3.710
A1
0.510
A2
3.200
3.600
0.126
0.142
B
0.380
0.570
0.015
0.022
B1
0.020
1.524 BSC
0.060
BSC
C
0.204
0.360
0.008
D
9.000
9.400
0.354
0.370
E
6.200
6.600
0.244
0.260
E1
7.320
7.920
0.288
0.312
e
2.540 (BSC)
0.014
0.100
BSC
L
3.000
3.600
0.118
0.142
E2
8.400
9.000
0.331
0.354
© 2013 Fremont Micro Devices Inc.
Confidential Rev0.80
DS838MBD/MDD-A0-Page11
Preliminary FT838MBD/838MDD
Fremont Micro Devices
Fremont Micro Devices (SZ) Limited
#5-8, 10/F, Changhong Building, Ke-Ji Nan 12 Road, Nanshan District, Shenzhen, Guangdong 518057
Tel: (86 755) 86117811
Fax: (86 755) 86117810
Fremont Micro Devices (Hong Kong) Limited
#16, 16/F, Blk B, Veristrong Industrial Centre, 34-36 Au Pui Wan Street, Fotan, Shatin, Hong Kong
Tel: (852) 27811186
Fax: (852) 27811144
Fremont Micro Devices (USA), Inc.
42982 Osgood Road Fremont, CA 94539
Tel: (1-510) 668-1321
Fax: (1-510) 226-9918
Web Site: http://www.fremontmicro.com/
* Information furnished is believed to be accurate and reliable. However, Fremont Micro Devices,
Incorporated (BVI) assumes no responsibility for the consequences of use of such information or for
any infringement of patents of other rights of third parties which may result from its use. No license is
granted by implication or otherwise under any patent rights of Fremont Micro Devices, Incorporated
(BVI). Specifications mentioned in this publication are subject to change without notice. This publication
supersedes and replaces all information previously supplied. Fremont Micro Devices, Incorporated
(BVI) products are not authorized for use as critical components in life support devices or systems
without express written approval of Fremont Micro Devices, Incorporated (BVI). The FMD logo is a
registered trademark of Fremont Micro Devices, Incorporated (BVI). All other names are the property of
their respective owners.
© 2013 Fremont Micro Devices Inc.
Confidential Rev0.80
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