PR9853

Low Cost Green-Power PWM Controller

With Low EMI Technique

Features
l Low Cost, PWM&PFM&hiccup mode l SOT-23-6L and DIP-8 Pb-Free
l Low Start-up Current (about 3μA) Packaging
l Low Operating Current (about 1.2mA) l Good Protection Coverage With Auto
l Current Mode Operation Self-Recovery
l VDD Under Voltage Lockout (UVLO) Complete Protection with
l Built-in Synchronized Slope
Ø Soft Clamped GATE output voltage
Compensation
18.0V
l Built-in Low EMI Technique
Ø VDD over voltage Clamp 34.0V
l Programmable PWM Frequency
Ø Cycle-by-cycle current limiting
l Audio Noise Free Operation
Ø Output SCP (Short circuit Protection)
l Leading edge Blanking on SEN input
Ø Output OLP (Over Load Protection)
l Constant output power limiting in
Ø High-Voltage CMOS Process with ESD
universal AC input Range

Applications
l Switching AC/DC Adapter l Set-Top Box Power Supplies
l Battery Charger l 384X Replacement
l Open Frame Switching Power Supply
l Standby Power Supplies

General Description
PR9853 is a highly integrated and low cost blanking circuit at current sense input
current mode PWM controller, which is could remove the signal glitch due to the
ideal for low power current mode of offline reverse recovery of diode in snubber
AC-DC fly-back converter applications. By circuit, and thus greatly reduces the
adjusting the external resistors to change amount of external components and the
the operating frequency, and then IC system cost for this design.
automatically enters PFM or hiccup mode Cycle-by-Cycle current limiting ensures a
in light-load or zero-load condition. safe operation even in the condition of
Thereby reduce the standby power loss short.
and achieve power-stored function. Excellent EMI performance is achieved by
Because of the very low start-up current, a built-in soft driver and low EMI technique.
large value start-up resistor can be used in The PR9853 offers rich protection features
PR9853.
such as VDD over voltage Clamp 、
Built-in synchronized slope compensation OLP(Over Load Protection) 、 SCP(Short
enhances the stability of the system and
circuit protection)、Sense Fault Protection
avoids sub-harmonic oscillation. The
dynamic peak current limiting circuit and OCP(Over current protection). The
reduces the variation of output power output voltage of PR9853 is softly clamped
which caused by system delay over a to maximum 18.0V to protect the power
universal AC input range. Leading edge MOSFET. PR9853 is offered in SOT-23-6L
and DIP-8 packages.

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PR9853 Low Cost Green-Power PWM Controller
With Low EMI Technique

Pin Assignment

Pin Descriptions
DIP8
PIN Name Description
1 GATE Totem output, to drive the gate of external power MOSFET.
2 VDD Supply voltage pin.
3 NC
4 SEN Current sense pin, a resistor connects, to sense the MOSFET current.
This pin is to program the switching frequency. By connecting a resistor
5 RI
to ground to set the switching frequency.
6 NC
Voltage feedback pin. Output current of this pin could controls the PWM
7 FB
duty cycle、OLP and SCP.
8 GND Ground Pin

SOT23-6
PIN Name Description
1 GND Ground Pin
Voltage feedback pin. Output current of this pin could controls the PWM
2 FB
duty cycle、OLP and SCP.
This pin is to program the switching frequency. By connecting a resistor
3 RI
to ground to set the switching frequency.
4 SEN Current sense pin, a resistor connects, to sense the MOSFET current.
5 VDD Supply voltage pin.
6 GATE Totem output, to drive the gate of external power MOSFET.

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PR9853 Low Cost Green-Power PWM Controller
With Low EMI Technique

Typical Application

Block Diagram

Simplified Internal Circuit Architecture

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PR9853 Low Cost Green-Power PWM Controller
With Low EMI Technique

Absolute Maximum Ratings

Symbol Parameter Rating Unit
VDD VDD DC Supply voltage 30 V
IOVP VDD Clamp maximal enter current 20 mA
VFB Input Voltage to FB Pin -0.3 to 6V V
VSEN Input Voltage to SEN Pin -0.3 to 6V V
VRI Input Voltage to RI Pin -0.3 to 6V V
Package Dissipation SOT-23-6 200 ℃/W
RθJA
Package Dissipation DIP8 60 ℃/W
ESD Capability, HBM Model 2500 V
ESD Capability, Machine Model 250 V
Lead Temperature SOT-23-6L (20S) 220 ℃
TL
(Soldering) DIP-8 (10S) 260 ℃
TSTG Storage Temperature Range -55 to + 150 ℃
TJ Operating Junction Temperature Range -20 to + 150 ℃

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PR9853 Low Cost Green-Power PWM Controller
With Low EMI Technique

Electrical Characteristics
(Ta=25°C unless otherwise noted, VDD = 16V)

Symbol Parameter Conditions Min. Typ. Max. Unit

Supply Voltage (VDD Pin)

IST Startup Current 3.0 20.0 μA

VFB=0V 3.0 6 mA

ISS Operating Current VFB=3V 1.2 4 mA

VFB=Open 0.8 3.5 mA

VDDON Turn-on Threshold Voltage 13.0 14.0 15.0 V

VDDOFF Turn-off Threshold Voltage 7.8 8.8 9.8 V

VDDCLAMP VDD Clamp Voltage IVDD=10mA 31 36 V

Anti Intermission Surge

VDDAIS 9.4 V
VDD Voltage

Voltage Feedback (FB Pin)

IFB Short Circuit Current VFB=0V 0.65 mA

VFB Open Loop Voltage VFB=Open 4.8 V

IFB_0D Zero Duty Cycle FB current 0.59 mA

VPFM Enter PFM Threshold VFB 1.80 V

Vhiccup Enter hiccup mode Threshold VFB 1.2 V

VOLP&SCP Enter OLP&SCP FB voltage 3.7 V

TOLP&SCP OLP&SCP min. delay Time RI=100K 33 40 50 mS

Current Sensing (SEN Pin)

SEN Maximum Voltage Level RI=100K,

VTH_L 0.80 V
（Dmin=0%） FB=3.3V
SEN Maximum Voltage RI=100K,
VTH_H 1.05 V
Level(Dmax=78%) FB=3.3V

TPD Delay to Output FB=3.3V 75 ns

RCS Input Impedance 40 KΩ

Leading edge blanking time

TLEB RI=100K 300 nS
( LEB )

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PR9853 Low Cost Green-Power PWM Controller
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Symbol Parameter Conditions Min. Typ. Max. Unit

Oscillator (RI Pin)

FOSC Normal Frequency RI=100Kohm 60 65 70 KHz

FPFM PFM Frequency RI=100Kohm 22 KHZ

DCMAX_W Maximum Duty Cycle PWM RI=100Kohm 78 %

DCMAX_F Maximum Duty Cycle PFM RI=100Kohm 78 %

ΔFTEMP Frequency Temp. Stability -30-100℃ 5 %

Fswing Frequency swing RI=100Kohm -4 4 %

GATE Drive Output (GATE Pin)

Output Low Level VDD=16V,

VOL 0.8 V
IO=20mA

Output High Level VDD=16V,

VOH 10 V
IO=20mA
TR Rising Time CL=1000pF 110 ns

TF Falling Time CL=1000pF 60 ns

VGCLAMP Output Clamp Voltage VDD=20V 18.0 V

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PR9853 Low Cost Green-Power PWM Controller
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Operation Description
Current Mode PWM switching frequency. The suggested
operating frequency range of PR9853 is
When the voltage of the sense resistor from 50 KHz to 150 KHz.
reaches the internal setting value VTH, the
register resets and the power MOSFET cuts
Green Power Operation
off. So, to detect and modulate the peak
current cycle-by-cycle could control the The dissipation of switching mode power
output power. The feedback current has a supply is highly concerned in zero load or
good linear modulation rate. It can increase light load condition. Different topologies
the dynamic response of input or output, have been applied in different chips,
and avoid the pole brought by inductance of however, the basic operation theory of all
output filter ,thus the system descends from these solutions tend to reduce the switching
two-pole to one-pole. So it widens the frequency under light-load or no-load
frequency range and optimizes the overload condition.
protection and short circuit protection.
The green power function of PR9853 adapts
PWM、PFM and hiccup mode combining
Startup Current and Under Voltage
modulation. When RI resistor is 100kΩ, the
Lockout PWM frequency is 65KHz at heavy load
The startup current of PR9853 is set to be operation. T PR9853 control output voltage
very low so that a large value startup through modifying the pulse width. The
resistor can be used to minimize the power voltage of FB pin decrease when the load is
loss. For AC/DC Adapter application, a 2 in light/medium condition, the switching
MΩ and 1/8 W startup resistor and a mode controller enters PFM when the
10uF/25V VDD hold capacitor could be feedback voltage is below 1.8V. The
used. operating frequency of oscillator descends
gradually. When the feedback voltage is
The turn-on and turn-off threshold of the 1.2V, the frequency decreases to be 22kHz,
PR9853 is designed to be 14V and 8.8V. and eliminates the audio noise.
During startup, the hold-up capacitor must
be charged to 14.0V through the startup
resistor. The hysteresis is to prevent the
shutdown from the voltage drop during
startup.

Internal Bias and OSC Operation

A resistor connected between RI pin and
GND pin sets that the internal constant
current source charge or discharge to the
internal fixed capacitor. The charge time and
discharge time decides the internal clock
frequency. Increasing the resistance will PR9853 Green-Power Function
reduce the input current and the switching
frequency. The relationship between RI and To decrease the standby dissipation,
PWM switching frequency follows the below PR9853 enters the hiccup mode. If the
equation within the RI allowed range. feedback voltage is below 1.2V and active,
MOSFET would have been cut off the until
6500 VDD voltage drops below preset level.
FOSC = (kHz ) Otherwise the MOSFET remains off state so
RI ( KΩ)
that obtain minimized power dissipation.
For example, a 100kΩ resistor RI could
generate 20uA constant current and 65kHz Internal Synchronized Slop

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PR9853 Low Cost Green-Power PWM Controller
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Compensation pull down the VDD voltage, then the circuit

is restart. To avoid the wrong operation
Although there are many advantages in the when circuit starts, the delay time is set to
current mode control than the conventional be 40ms with the RI resistance is 100Kohm.
voltage mode control, there are still several The relationship between RI and TOLP&SCP
drawbacks for peak-sensing current-mode follows the below equation.
converter, especially the instability of open
loop when duty-cycle is higher than 50%. To RI × 2 RI × 3
solve this problem, PR9853 introduces an (mS ) < TOLP& SCP < (mS )
6 × 10 3
6 × 10 3
internal slope compensation, adding voltage
ramp to the current sense input voltage for
PWM generation. It improves the stability of
Leading-edge Blanking (LEB)
close loop greatly at CCM, prevents the Each time the power MOSFET is switched
sub-harmonic oscillation, and thus reduces on, a turn-on spike will inevitably occur at
the output ripple voltage. the SEN pin, which would disturb the
internal signal from the sampling of the RSEN.
Current Sensing & Dynamic peak There is a 300ns leading edge blanking time
limiting built in to avoid the effect of the turn-on
spike, and the power MOSFET cannot be
The current flowing by the power MOSFET switched off during this moment, thus the
is detected from SEN voltage VSEN external RC filter on SEN input is no longer
cycle-by-cycle, which would be compared to required.
the internal reference voltage, and thereby
controls the reverse of the internal register,
limits the primary peak current IMAX of the
transformer. The transformer energy
1
E= × L × I MAX . So adjusting the RSEN
2

2
can set the maximal output power. The
current flowing by the power MOSFET has
V IN
an extra value ( ∆I = × TD ) due to the
LP
system delay that is from detecting the
current through the SEN pin to power
MOSFET off in PR9853 (Among these, VIN is
the primary winding voltage of the
transformer and LP is the primary wind
inductance). VIN ranges from 85Vac to
264Vac. To guarantee the output power is a VDD over Clamp
constant for universal input AC voltage, a
dynamic peak limit circuit is designed to There is a 34V VDD over-voltage clamp
compensate the system delay time. circuit in PR9853 to improve the credibility
and extend the life of the chip. When the
OLP&SCP VDD voltage is over 34V, the GATE pin will
be shutdown immediately and the VDD
To protect the circuit from being damaged voltage descend rapidly.
due to over load or short , a smart
OLP&SCP function is added in PR9853. GATE Driver
When short or over load occurs in the output
end, the feedback cycle would enhance the The output of PR9853 designs a totem pole
voltage of FB pin. When the voltage is over to drive a external power MOSFET. The
3.7V, the internal detective circuit would dead time is introduced to minimize the
send a signal to shut down the GATE and transfixion current during the output

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PR9853 Low Cost Green-Power PWM Controller
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operating. The soft clamp technology is As following figure shows, the internal
introduced to protect the external power oscillation frequency is modulated by itself.
MOSFET from breaking down . A whole surge cycle includes 128 pulses
and the swing ranges from -4% to +4%.
Low EMI technique Thus, the function could minimize the
electromagnetic interfere of the power
Low EMI technique is introduced in PR9853. supply module.

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PR9853 Low Cost Green-Power PWM Controller
With Low EMI Technique

Characterization Plots
VDD=16V,RI=100Kohm,TA=25℃ condition applies if not otherwise noted.

VDD Start Current Vs. Voltage I_vdd_startup vs Temp

20 2.5

I_vdd_startup (uA)
15 2.0
Ist(uA)

1.5
10
1.0
5
0.5
0 0.0
0 2 4 6 8 10 12 14 16 -30 -10 10 30 50 70 90 110 130 150
VDD(V) Temp(℃)

VDD Operation Current Vs. Load(pF) UVLO(on) vs Temp

8 8.8
132KHz 8.6
6
UVLO(on) (V)

8.4
Idd(mA)

4 67KHz 8.2

2 50KHz 8
7.8
0 7.6
0 500 1000 1500 2000 -30 -10 10 30 50 70 90 110 130 150
Gate Load(pF) Temp(℃)

UVLO(OFF) vs Temp Fosc Vs. RI

14.2 140
120
14.0
100
UVLO(OFF) (V)

Fosc（KHz）

13.8 80
60
13.6
40
13.4 20
13.2 0
-30 -10 10 30 50 70 90 110 130 150 50 70 90 110 130 150
Temp(℃) RI(Kohm)

Fosc(KHz) vs Temp Vth_OC Vs. Duty_cycle

70 1.1

68 1.0
Fosc(KHz)

66 0.9
Vth_OC(V)

64 0.8

62 0.7

60 0.6
-30 -10 10 30 50 70 90 110 130 150 0 20 40 60 80
Temp(℃) Duty_cycle(%)

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PR9853 Low Cost Green-Power PWM Controller
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Package Dimensions

DIP-8L

Dimensions
Millimeters Inches
Symbol
Min. Typ. Max. Min. Typ. Max.
A 5.334 0.210
A1 0.381 0.015
A2 3.175 3.302 3.429 0.125 0.130 0.135
b 1.524 0.060
b1 0.457 0.018
D 9.017 9.271 10.160 0.355 0.365 0.400
E 7.620 0.300
E1 6.223 6.350 6.477 0.245 0.250 0.255
e 2.540 0.100
L 2.921 3.302 3.810 0.115 0.130 0.150
eB 8.509 9.017 9.525 0.335 0.355 0.375
θ˚ 0˚ 7˚ 15˚ 0˚ 7˚ 15˚

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PR9853 Low Cost Green-Power PWM Controller
With Low EMI Technique

SOT-23-6L

Dimensions
Dimensions In Millimeters Dimensions In Inches
Symbol
Min Max Min Max
A 0.700 1.000 0.028 0.039
A1 0.000 0.100 0.000 0.004
B 1.397 1.803 0.055 0.071
b 0.300 0.559 0.012 0.022
C 2.591 3.000 0.102 0.118
D 2.692 3.099 0.106 0.122
e 0.838 1.041 0.033 0.041
H 0.080 0.254 0.003 0.010
L 0.300 0.610 0.012 0.024

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