UNISONIC TECHNOLOGIES CO., LTD
USRB02
Preliminary
LINEAR INTEGRATED CIRCUIT
HIGH PRECISION CC/CV
PRIMARY SIDE SWITCH
DESCRIPTION
The UTC
USRB02
is a primary controller for charger and
adapter applications. The controlled variable is transferred by an
auxiliary winding from the secondary to the primary side. The
device operates in Pulse Frequency Modulation (PFM) in CC
mode as well at large load condition and it operates in Pulse
Width Modulation (PWM) with frequency reduction at
light/medium load condition.
The UTC
USRB02
operates in primary-side sensing and
regulation. Opto-coupler and TL431 could be eliminated. It also
eliminates the need of loop compensation circuitry while
maintaining stability.
The UTC
USRB02
achieves high precision CV/CC regulation
and high power efficiency. It offers comprehensive protection
coverage with auto-recovery features including Cycle-by-cycle
current limiting, output over voltage protection, V
DD
over voltage
protection, feedback loop open protection, short circuit protection,
leading edge blanking, OTP, V
DD
under voltage lockout, etc.
SOP-8
FEATURES
* Programmable cable drop compensation
* Built-in leading edge blanking
* Built-in primary winding inductance compensation
* Built-in line voltage compensation
* Audio noise free operation
* Open circuit protection
* Output over voltage protection
* VDD over voltage protection
* Short circuit protection
* Over temperature protection
* ±5% constant voltage regulation at universal AC input
* Primary side control without TL431 and opto-coupler
* High precision constant current regulation at universal AC
input
* Programmable CV and CC regulation
* Eliminates control loop compensation circuitry
* Flyback topology in DCM operation
* Random frequency modulation to reduce system EMI
* Built-in power NPN
* Multi-mode operation for efficiency improving
ORDERING INFORMATION
Ordering Number
USRB02G-S08-R
Package
SOP-8
Packing
Tape Reel
USRB02G-S08-R
(1)Packing Type
(2)Package Type
(3)Green Package
(1) R: Tape Reel
(2) S08: SOP-8
(3) G: Halogen Free and Lead Free
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Copyright © 2015 Unisonic Technologies Co., Ltd
1 of 7
QW-R103-087.a
USRB02
MARKING
Preliminary
`
LINEAR INTEGRATED CIRCUIT
PIN CONFIGURATION
V
DD
FB
NC
CS
1
2
3
4
8
7
6
5
GND
GND
C
C
PIN DESCRIPTION
PIN NAME
V
DD
FB
NC
CS
C
GND
DESCRIPTION
Power supply
The voltage feedback from the auxiliary winding
NC
Current sense input
The collector of the power NPN
Ground
PIN NO.
1
2
3
4
5~6
7~8
BLOCK DIAGRAM
UNISONIC TECHNOLOGIES CO., LTD
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QW-R103-087.a
USRB02
PARAMETER
Preliminary
`
LINEAR INTEGRATED CIRCUIT
ABSOLUTE MAXIMUM RATING
SYMBOL
RATINGS
UNIT
V
DD
Voltage
-0.3~30
V
C Voltage
-0.3~700
V
CS Input Voltage
-0.3~7
V
FB Input Voltage
-0.3~7
V
Junction Temperature
T
J
-40~150
°C
Storage Temperature
T
STG
-55~150
°C
Lead Temperature (Soldering, 10 secs)
T
OPR
260
°C
Note: Absolute maximum ratings are those values beyond which the device could be permanently damaged.
Absolute maximum ratings are stress ratings only and functional device operation is not implied.
THERMAL DATA
SYMBOL
θ
JC
RATINGS
150
UNIT
°C/W
PARAMETER
Junction to Ambient
ELECTRICAL CHARACTERISTICS
(T
A
=25°C, VDD=15V, if not otherwise noted)
SYMBOL
I
ST
I
OP
V
TH(OFF)
V
TH (ON)
V
DD_OVP
TEST CONDITIONS
V
DD
= V
TH (ON)
-1V
6.5
18.4
26.5
MIN
TYP
5
0.72
7.1
19.4
28
MAX UNIT
15
1.0
7.8
20.4
29.5
26
μA
mA
V
V
V
V
μS
mV
mV
mV
uS
nS
PARAMETER
Supply Voltage (V
DD
) Section
Start up Current
Static Current
Turn-off Threshold Voltage
Turn-on Threshold Voltage
V
DD
Over Protect Voltage
Operating Voltage
Current Sense Input Section
LEB Time
Minimum Over Current Threshold
Maximum Over Current Threshold
Minimum CS threshold
Maximum Ton
OCP Propagation Delay
T
LEB
Vth_ocp_min
Vth_ocp_max
Vcs_mini
Ton_max
T
D_OC
From OCP Comparator to Base
Drive
485
0.5
500
555
100
50
100
515
FB Input Section
Reference Voltage for Feedback
V
FB
Threshold
Minimum Toff
Tpause_min
Minimum frequency
F_min
Maximum Cable Compensation
Icable
Current
Output over voltage threshold
V_ovp
Power BJT Section
Collector-emitter breakdown voltage
V
CEO
Collect Peak Current
I
C
Collector-Base Breakdown Voltage
V
CBO
On Chip Over Temperature Section
Over Temperature Protection
T_otp
Over Temperature Protection
T_otp_rec
recovery point
2.475
720
2.5
2.0
800
48
2.525
880
V
uS
Hz
μA
2.85
I
C
=10mA, I
B
=0
I
C
=10mA
450
3.00
3.15
V
V
A
V
°C
°C
0.6
700
165
130
UNISONIC TECHNOLOGIES CO., LTD
www.unisonic.com.tw
3 of 7
QW-R103-087.a
USRB02
Preliminary
`
LINEAR INTEGRATED CIRCUIT
OPERATION DESCRIPTION
The UTC
USRB02
is a primary control unit for switch mode charger and adapter applications. It operates in
primary-side sensing and regulation. Opto-coupler and TL431 could be eliminated. Proprietary built-in CV and CC
control can achieve high precision CV/CC performance. It uses Pulse Frequency Modulation (PFM) and Pulse Width
Modulation (PWM) method to build discontinuous conduction mode (DCM) flyback power supplies.
Startup control
The V
DD
pin of UTC
USRB02
is connected to the line input through a resistor. A large value startup resistor can be
used to minimize the power loss in application because the start current of UTC
USRB02
is very low. When the V
DD
voltage reaches V
TH (ON)
, the internal startup circuit is disabled and the IC turns on.
Operating Current
The Operating current of UTC
USRB02
is as low as 720μA. Good efficiency and very low standby power can be
achieved.
Constant Voltage Operation
The output voltage is defined by the transmission ratio between the secondary and auxiliary winding. The UTC
USRB02
captures the auxiliary winding feedback voltage at FB pin and operates in constant-voltage (CV) mode to
regulate the output voltage. The auxiliary voltage reflects the output voltage is given by:
N
V
AUX
=
A
× V
O
+
∆
V
）
（
(1)
N
S
Where
△
V indicates the drop voltage of the output diode.
Figure 2. Auxiliary voltage waveform
Via a resistor divider connected between the auxiliary winding and FB, the V
AUX
is sampled at the Tsampling end
and it is hold until the next sampling. The sampled voltage is compared with 2.5V reference voltage and the error is
amplified. The error amplifier output reflects the load condition and controls the Toff time to regulate the output
voltage, thus constant output voltage can be achieved.
Constant Current Operation
When the sampled voltage is below 2.5V reference voltage and the error amplifier output reaches its maximum,
thus UTC
USRB02
operates in constant-current (CC) mode. The CC point and maximum output power can be
externally adjusted by external current sense resistor Rcs. The larger Rcs, the smaller CC point is, and the smaller
output power becomes.
UNISONIC TECHNOLOGIES CO., LTD
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QW-R103-087.a
USRB02
Preliminary
`
LINEAR INTEGRATED CIRCUIT
OPERATION DESCRIPTION (Cont.)
Vout
Large
Rcs
Small
Rcs
Iout
Figure3. Adjustable output power by changing Rcs
Figure4. Secondary current waveform
In CC operation, the CC loop control function of UTC
USRB02
will keep a fixed proportion between secondary
inductance de-magnetization time (Tdemag) and switching cycle time (Tsw). The fixed proportion is
T
demag
1
(2)
=
T
SW
2
Thus the output current is given by:
I
out
=
T
demag
1 N
P
1 N
P
×
× I
PK
×
= ×
×I
2 N
S
T
SW
4 N
S PK
(3)
Programmable Cable drop Compensation
UTC
USRB02
has a built-in cable voltage drop compensation to achieve good load regulation. An offset voltage is
generated at FB pin by an internal current flowing into the resistor divider. it is inversely proportional to the output
load current. The voltage drop across the cable is compensated by this offset voltage at FB pin. It can also be
programmed by adjusting the resistance of the divider to compensate the drop for various cable lines used.
Current Sensing and Leading Edge Blanking
Cycle-by-cycle current limiting is offered in UTC
USRB02
. The switch current is detected by a sense resistor into
the CS pin. When the power switch is turned on, a turn-on spike will occur on this resistor. A 500ns leading-edge
blanking is built in to avoid false-termination of the switching pulse so that the external RC filtering is no longer
needed.
UNISONIC TECHNOLOGIES CO., LTD
www.unisonic.com.tw
5 of 7
QW-R103-087.a
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