OB2262CPA [ETC]
Current Mode PWM Controller;
| 型号： | OB2262CPA |
| 厂家： | 
ETC |
| 描述： | Current Mode PWM Controller |
| 文件： | 总13页 (文件大小：402K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
OB2262
Current Mode PWM Controller
The tone energy at below 20KHZ is minimized in the
design and audio noise is eliminated during operation.
OB2262 is offered in SOT23-6, SOP-8 and DIP-8
packages.
GENERAL DESCRIPTION
OB2262 is a highly integrated current mode PWM
control IC optimized for high performance, low
standby power and cost effective offline flyback
converter applications in sub 30W range.
FEATURES
PWM switching frequency at normal operation is
externally programmable and trimmed to tight range.
At no load or light load condition, the IC operates in
extended ‘burst mode’ to minimize switching loss.
Lower standby power and higher conversion
efficiency is thus achieved.
■
Extended Burst Mode Control For Improved
Efficiency and Minimum Standby Power Design
Audio Noise Free Operation
External Programmable PWM Switching
Frequency
Internal Synchronized Slope Compensation
Low VDD Startup Current and Low Operating
Current (1.4mA)
Leading Edge Blanking on Current Sense Input
Good Protection Coverage With Auto Self-
Recovery
■
■
■
■
VDD low startup current and low operating current
contribute to a reliable power on startup design with
OB2262. A large value resistor could thus be used in
the startup circuit to minimize the standby power.
The internal slope compensation improves system
large signal stability and reduces the possible sub-
harmonic oscillation at high PWM duty cycle output.
Leading-edge blanking on current sense(CS) input
removes the signal glitch due to snubber circuit diode
reverse recovery and thus greatly reduces the external
component count and system cost in the design.
OB2262 offers complete protection coverage with
automatic self-recovery feature including Cycle-by-
Cycle current limiting (OCP), over load protection
(OLP), VDD over voltage clamp and under voltage
lockout (UVLO). The Gate-drive output is clamped
to maximum 18V to protect the power MOSFET.
Excellent EMI performance is achieved soft
switching control at the totem pole gate drive output.
■
■
o
VDD Over Voltage Clamp and Under Voltage
Lockout with Hysteresis (UVLO)
o
o
Gate Output Maximum Voltage Clamp (18V)
On-Bright Proprietary Line Input Compensated
Cycle-by-Cycle Over-current Threshold Setting
For Constant Output Power Limiting Over
Universal Input Voltage Range.
o
Overload Protection (OLP).
APPLICATIONS
Offline AC/DC flyback converter for
■
■
■
■
Battery Charger
Power Adaptor
Set-Top Box Power Supplies
Open-frame SMPS
TYPICAL APPLICATION
E M I
4
2
A C I N
F i l t e r
+
+
DC OUT
+
V DD
G A T E
O B 2 2 6 2
R I
S E N S E
O B 4 3 1
F B
G N D
©On-Bright Electronics
Confidential to Micro Bridge
- 1 -
OB_DOC_DS_62B5
OB2262
Current Mode PWM Controller
Ordering Information
GENERAL INFORMATION
Pin Configuration
The OB2262 is offered in SOT23-6, DIP8 and SOP8
packages, shown as below.
Part Number
OB2262MP
OB2262AP
OB2262CP
Description
SOT23-6, Pb-free
DIP8, Pb-free
SOP8, Pb-free
Package Dissipation Rating
Package
RθJA
(°C/W)
DIP8
90
SOP8
150
200
SOT23-6
Absolute Maximum Ratings
Parameter
Value
VDD DC Supply Voltage
VDD Zener Clamp
VoltageNote
30 V
VDD_Clamp+0.1V
VDD DC Clamp Current
VFB Input Voltage
VSENSE Input Voltage to
Sense Pin
10 mA
-0.3 to 7V
-0.3 to 7V
VRI Input Voltage to RI Pin -0.3 to 7V
Min/Max Operating
Junction Temperature TJ
Min/Max Storage
-20 to 150 oC
-55 to 160 oC
Temperature Tstg
Note: VDD_Clamp has a nominal value of 34V.
Stresses beyond those listed under “absolute maximum ratings”
may cause permanent damage to the device. These are stress
ratings only, functional operation of the device at these or any
other conditions beyond those indicated under “recommended
operating conditions” is not implied. Exposure to absolute
maximum-rated conditions for extended periods may affect device
reliability.
©On-Bright Electronics
Confidential to Micro Bridge
- 2 -
OB_DOC_DS_62B5
OB2262
Current Mode PWM Controller
Marking Information
TERMINAL ASSIGNMENTS
Pin Name
GND
FB
I/O Description
P
I
Ground
Feedback input pin. The PWM duty cycle is determined by voltage level into this pin and
the current-sense signal at Pin 6.
RI
I
Internal Oscillator frequency setting pin. A resistor connected between RI and GND sets
the PWM frequency.
SENSE
VDD
GATE
I
P
O
Current sense input pin. Connected to MOSFET current sensing resistor node.
Chip DC power supply pin.
Totem-pole gate drive output for the power MOSFET.
RECOMMENDED OPERATING CONDITION
Symbol
Parameter
Min
Unit
Max
VDD
RI
TA
VDD Supply Voltage
RI Resistor Value
Operating Ambient Temperature
10 to 30
100
-20 to 85
V
Kohm
oC
©On-Bright Electronics
Confidential to Micro Bridge
- 3 -
OB_DOC_DS_62B5
OB2262
Current Mode PWM Controller
BLOCK DIAGRAM
©On-Bright Electronics
Confidential to Micro Bridge
- 4 -
OB_DOC_DS_62B5
OB2262
Current Mode PWM Controller
ELECTRICAL CHARACTERISTICS
(TA = 25OC if not otherwise noted)
Symbol
Parameter
Test Conditions
Min
Typ
Max
Unit
Supply Voltage (VDD)
I_VDD_Stup
VDD Start up Current
VDD =12.5V, RI=100K
Measure Leakage current
into VDD
3
20
uA
I_VDD_Ops
UVLO(ON)
UVLO(OFF)
Operation Current
VDD=16V,
RI=100Kohm, VFB=3V
1.4
8.8
14
mA
V
VDD Under Voltage
Lockout Enter
VDD Under Voltage
Lockout Exit
7.8
13
9.8
15
V
(Recovery)
VDD_Clamp
VDD Zener Clamp
Voltage
IVDD = 5 mA
34
V
Feedback Input Section(FB Pin)
AVCS
VFB_Open
IFB_Short
PWM Input Gain
2.0
4.8
1.2
V/V
V
mA
ΔVFB /ΔVcs
VFB Open Loop Voltage
FB pin short circuit
current
Zero Duty Cycle FB
Threshold Voltage
Power Limiting FB
Threshold Voltage
Power limiting
Short FB pin to GND and
measure current
VDD = 16V,
VTH_0D
VTH_PL
TD_PL
0.75
V
RI=100Kohm
3.7
35
V
mSec
Debounce Time
ZFB_IN
DC_MAX
Input Impedance
Maximum Duty Cycle
6
75
Kohm
%
VDD=18V,
RI=100Kohm, FB=3V,
CS=0
Current Sense Input(Sense Pin)
T_blanking
Leading edge blanking RI = 100 Kohm
300
ns
time
ZSENSE_IN
TD_OC
Input Impedance
Over Current Detection VDD = 16V,
40
75
Kohm
nSec
and Control Delay
Over-Current
Threshold Voltage or
Equivalent maximum
input voltage at SENSE
CS>VTH_OC, FB=3.3V
FB=3.3V, RI=100 Kohm
VTH_OC
0.70
60
0.75
0.80
70
V
Oscillator
FOSC
Normal Oscillation
Frequency
Frequency Temperature VDD = 16V,
RI = 100 Kohm
65
5
KHZ
%
∆f_Temp
∆f_VDD
Stability
RI=100Kohm, TA -20oC
to 100 oC
Frequency Voltage
Stability
VDD = 12-25V,
RI=100Kohm
5
%
RI_range
V_RI_open
Fosc_BM
Operating RI Range
RI open load voltage
Burst Mode Base
Frequency
50
100
2
22
150
Kohm
V
KHZ
VDD = 16V, RI =
100Kohm
©On-Bright Electronics
Confidential to Micro Bridge
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OB_DOC_DS_62B5
OB2262
Current Mode PWM Controller
Gate Drive Output
VOL
VOH
V_Clamp
Output Low Level
VDD = 16V, Io = -20 mA
VDD = 16V, Io = 20 mA
0.8
V
V
V
Output High Level
Output Clamp Voltage
Level
10
18
T_r
T_f
Output Rising Time
Output Falling Time
VDD = 16V, CL = 1nf
VDD = 16V, CL = 1nf
220
70
nSec
nSec
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Confidential to Micro Bridge
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OB_DOC_DS_62B5
OB2262
Current Mode PWM Controller
CHARACTERIZATION PLOTS
VDD = 16V, RI = 100 Kohm, TA = 25oC condition applies if not otherwise noted.
VDD Startup Current vs. Voltage
I_VDD_startup vs. Temp
5.0
4.6
4.2
3.8
3.4
3.0
20
15
10
5
0
0 2 4 6 8 10 12 14 16
-20
10
40
70
100
130
VDD(V)
Temp(C)
VDD UVLO and Ops Current
VDD Operation Current vs. Load(pF)
50KHz 65KHz 100KHz
2
1.6
1.2
0.8
0.4
0
5
4
3
2
1
0
0
500
1000
1500
2000
0
5
10
15
VDD (V)
20
25
30
Gat e Load (pF)
UVLO(ON) vs Temp
UVLO(OFF) vs Temp
14.5
14.4
14.3
14.2
14.1
14.0
9.0
8.8
8.6
8.4
8.2
8.0
-20
10
40
70
100
130
-20
10
40
70
100
130
Temp(C)
Temp(C)
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OB_DOC_DS_62B5
OB2262
Current Mode PWM Controller
Fosc vs. Temp
Fosc(KHz) vs. RI(Kohm)
66.5
66
140
115
90
65.5
65
64.5
64
65
40
63.5
50
70
90 110 130 150
RI(Kohm)
-20
5
30
55
80
105
130
Temp (C)
Vth_OC(V) vs Duty_cycle(%)
1.2
1.1
1
0.9
0.8
0.7
0 10 20 30 40 50 60 70
Duty_cycle(%)
©On-Bright Electronics
Confidential to Micro Bridge
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OB_DOC_DS_62B5
OB2262
Current Mode PWM Controller
OPERATION DESCRIPTION
The OB2262 is a highly integrated PWM controller
IC optimized for offline flyback converter
applications in sub 30W power range. The extended
burst mode control greatly reduces the standby
power consumption and helps the design easily
meet the international power conservation
requirements.
is determined. The relationship between RI and
switching frequency follows the below equation
within the specified RI in Kohm range at nominal
loading operational condition.
6500
FOSC
=
(Khz)
RI(Kohm)
•
Startup Current and Start up Control
•
Current Sensing and Leading Edge Blanking
Startup current of OB2262 is designed to be very
low so that VDD could be charged up above UVLO
threshold level and device starts up quickly. A large
value startup resistor can therefore be used to
minimize the power loss yet provides reliable
startup in application. For AC/DC adaptor with
universal input range design, a 2 MΩ, 1/8 W
startup resistor could be used together with a VDD
capacitor to provide a fast startup and low power
dissipation solution.
Cycle-by-Cycle current limiting is offered in
OB2262 current mode PWM control. The switch
current is detected by a sense resistor into the sense
pin. An internal leading edge blanking circuit chops
off the sense voltage spike at initial MOSFET on
state due to Snubber diode reverse recovery so that
the external RC filtering on sense input is no longer
required. The current limit comparator is disabled
and thus cannot turn off the external MOSFET
during the blanking period. PWM duty cycle is
determined by the current sense input voltage and
the FB input voltage.
•
Operating Current
The Operating current of OB2262 is low at 1.4mA.
Good efficiency is achieved with OB2262 low
operating current together with extended burst
mode control features.
•
Internal Synchronized Slope Compensation
Built-in slope compensation circuit adds voltage
ramp onto the current sense input voltage for PWM
generation. This greatly improves the close loop
stability at CCM and prevents the sub-harmonic
oscillation and thus reduces the output ripple
voltage.
•
Extended Burst Mode Operation
At zero load or light load condition, majority of the
power dissipation in a switching mode power
supply is from switching loss on the MOSFET
transistor, the core loss of the transformer and the
loss on the snubber circuit. The magnitude of
power loss is in proportion to the number of
switching events within a fixed period of time.
Reducing switching events leads to the reduction
on the power loss and thus conserves the energy.
OB2262 self adjusts the switching mode according
to the loading condition. At from no load to
light/medium load condition, the FB input drops
below burst mode threshold level. Device enters
Burst Mode control. The Gate drive output switches
only when VDD voltage drops below a preset level
and FB input is active to output an on state.
Otherwise the gate drive remains at off state to
minimize the switching loss and reduces the
standby power consumption to the greatest extend.
The frequency control also eliminates the audio
noise at any loading conditions.
•
Gate Drive
OB2262 Gate is connected to an external MOSFET
gate for power switch control. Too weak the gate
drive strength results in higher conduction and
switch loss of MOSFET while too strong gate drive
output compromises the EMI.
A good tradeoff is achieved through the built-in
totem pole gate design with right output strength
and dead time control. The low idle loss and good
EMI system design is easier to achieve with this
dedicated control scheme. An internal 18V clamp is
added for MOSFET gate protection at higher than
expected VDD input.
•
Protection Controls
Good power supply system reliability is achieved
with its rich protection features including Cycle-by-
Cycle current limiting (OCP), Over Load
Protection (OLP) and over voltage clamp, Under
Voltage Lockout on VDD (UVLO).
•
Oscillator Operation
A resistor connected between RI and GND sets the
constant current source to charge/discharge the
internal cap and thus the PWM oscillator frequency
With On-Bright Proprietary technology, the OCP
threshold tracks PWM Duty cycles and is line
voltage compensated to achieve constant output
©On-Bright Electronics
Confidential to Micro Bridge
- 9 -
OB_DOC_DS_62B5
OB2262
Current Mode PWM Controller
power limit over the universal input voltage range
with recommended reference design.
VDD is supplied by transformer auxiliary winding
output. It is clamped when VDD is higher than
threshold value. The power MOSFET is shut down
when VDD drops below UVLO limit and device
enters power on start-up sequence thereafter.
At overload condition when FB input voltage
exceeds power limit threshold value for more than
TD_PL, control circuit reacts to shut down the
output power MOSFET. Device restarts when VDD
voltage drops below UVLO limit.
©On-Bright Electronics
Confidential to Micro Bridge
- 10 -
OB_DOC_DS_62B5
OB2262
Current Mode PWM Controller
PACKAGE MECHANICAL DATA
SOT23-6
©On-Bright Electronics
Confidential to Micro Bridge
- 11 -
OB_DOC_DS_62B5
OB2262
Current Mode PWM Controller
8-Pin Plastic DIP
©On-Bright Electronics
Confidential to Micro Bridge
- 12 -
OB_DOC_DS_62B5
OB2262
Current Mode PWM Controller
8-Pin Plastic SOP
©On-Bright Electronics
Confidential to Micro Bridge
- 13 -
OB_DOC_DS_62B5
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