CYStech Electronics Corp.
High Performance Current Mode PWM Controllers
Spec. No. : C510P8
Issued Date : 2003.04.24
Revised Date :
Page No. : 1/15
PL384XBP8
Description
The PL384XBP8 family of control ICs provides the necessary features to implement off-line or DC to DC fixed
frequency current mode control schemes with a minimal external parts count. Internally implemented circuits
include a trimmed oscillator for precise duty cycle control, under voltage lockout featuring start-up current less than
0.5mA, a precision reference trimmed for accuracy at the error amp input, logic to insure latched operation, a PWM
comparator which also provides current limit control, and a totem pole output stage designed to source or sink high
peak current. The output stage, suitable for driving N-channel MOSFETs, is low in the off-state.
Differences between members of this family are the under-voltage lockout thresholds and maximum duty cycle
ranges. The PL3842B and PL3844B have UVLO thresholds of 16V (on) and 10V (off), ideally suited off-line
applications. The corresponding thresholds for the PL3843B and PL3845B are 8.5V and 7.9V. The PL3842B and
PL3843B can operate to duty cycles approaching 100%. A range of the zero to <50% is obtained by the PL3844B
and PL3845B by the addition of an internal toggle flip flop which blanks the output off every other clock cycle.
Features
•
Trimmed oscillator for precise frequency control
•
Oscillator frequency guaranteed at 250 kHz
•
Current mode operation to 500kHz
•
Automatic feed forward compensation
•
Latching PWM for cycle-by-cycle current limiting
•
Internally trimmed reference with undervoltage lockout
•
High current totem pole output
•
Undervoltage lockout with hysteresis
•
Low start-up and operating current
Block Diagram
( toggle flip flop used only in PL3844B and PL3845B)
VI
7
34V
5
UVLO
S/R
5V
REF
8
GROUND
VREF
5V50mA
2.50V
INTERNAL
BIAS
VREF GOOD
LOGIC
6
OUTPUT
4
RT/CT
OSC
ERROR AMP.
VFB
2
T
2R
R
1V
S
R
CURRENT
SENSE
COMPARATOR
PWM
LATCH
COMP
1
CURRENT
SENSE
3
PL3842B
CYStek Product Specification
PL384XBP8
CYStech Electronics Corp.
Absolute Maximum Ratings
Symbol
V
I
V
I
I
O
E
O
Ptot
Tstg
T
J
T
L
Parameter
Supply Voltage (low impedance source)
Supply Voltage (Ii<30mA)
Output Current
Output Energy (capacitive load)
Analog Inputs (pins 2, 3)
Error Amplifier Output Sink Current
Power Dissipation at Tamb≤ 25℃
Storage Temperature Range
Junction Operating Temperature
Lead Temperature (soldering 10s)
Spec. No. : C510P8
Issued Date : 2003.04.24
Revised Date :
Page No. : 2/15
Value
30
Self Limiting
±
1
5
-0.3 to 5.5
10
1.25
-65 to +150
-40 to +150
300
Unit
V
A
µJ
V
mA
W
℃
℃
℃
Note : All voltages are with respect to pin 5, all currents are positive into the specified terminal.
Pin Connection
(top view)
COMP
V
FB
I
SENSE
R
T
/C
T
V
REF
V
CC
OUTPUT
GROUND
Pin Functions
No Function
1 COMP
2
3
4
5
6
7
8
V
FB
I
SENSE
R
T
/C
T
GROUND
OUTPUT
V
CC
V
REF
Description
This pin is the Error Amplifier output and is made available for loop compensation.
This is the inverting input of the Error Amplifier. It is normally connected to the switching
power supply output through a resistor divider.
A voltage proportional to inductor current is connected to this input. The PWM uses this
information to terminate the output switch conduction.
The oscillator frequency and maximum output duty cycle are programmed by connecting
resistor R
T
to V
REF
and capacitor C
T
to ground. Operation to 500kHz is possible.
This pin is the combined control circuitry and power ground.
This output directly drives the gate of a power MOSFET. Peak currents up to 1A are sourced
and sunk by this pin.
This pin is the positive supply of the control IC.
This is the reference output. It provides charging current for capacitor C
T
through resistor R
T
.
Thermal Data
Symbol
R
th, j-amb
Description
Thermal Resistance, junction to ambient
Value
100
Unit
℃/W
PL384XBP8
CYStek Product Specification
CYStech Electronics Corp.
Spec. No. : C510P8
Issued Date : 2003.04.24
Revised Date :
Page No. : 3/15
Electrical Characteristics
(〔note 1〕Unless otherwise stated, these specifications apply for
0≤T
amb
≤70℃,V
i
=15V(note 5),R
T
=10k,C
T
=3.3nF)
Parameter
Reference Section
Output Voltage
Line Regulation
Load Regulation
Temperature Stability
Total Output Variation
Output Noise Voltage
Long Term Stability
Output Short Circuit
Oscillator Section
Frequency
Frequency Change with Volt
Frequency Change with Temp
Oscillator Voltage Swing
Discharge Current (Vosc=2V)
Error Amp Section
Input Voltage
Input Bias Current
A
VOL
Unity Gain Bandwidth
Power Supply Rejec. Ratio
Output Sink Current
Output Source Current
V
OUT
High
V
OUT
Low
Current Sense Section
Gain
Maximum Input Signal
Supply Voltage Rejection
Input Bias Current
Delay to Output
Output Section
Output Low Level
Output High Level
UVLO Saturation
Rise Time
Fall Time
PL384XBP8
Test Conditions
Tj=25℃,I
O
=1mA
12V
≤
V
I
≤
25V
1mA
≤
I
O
≤
20mA
(Note 2)
Line, Load, Temperature
10Hz
≤
f
≤10kHz,Tj=25℃
(note 2)
Tamb=125℃, 1000 Hrs (note 2)
Symbol
V
REF
∆V
REF
∆V
REF
∆V
REF /
∆T
Min. Typ. Max.
4.9
5.0
5.1
-
2
20
-
3
25
-
0.2
-
4.82
-
5.18
-
50
-
-
5
25
-30 -100 -180
49
48
225-
-
-
-
7.8
7.6
2.42
-
65
0.7
60
2
-0.5
5
-
2.85
0.9
-
-
-
-
-
13
12
-
-
-
52
-
250
0.2
0.5
1.6
8.3
-
55
56
275
1.0
1.0
-
8.8
8.8
Unit
V
mV
mV
mV/℃
V
µV
mV
mA
kHz
kHz
kHz
%
%
V
mA
mA
V
µA
dB
MHz
dB
mA
mA
V
V
V/V
V
dB
µA
ns
V
V
V
V
V
ns
ns
e
N
I
SC
Tj=25℃
TA= 0 to 70
℃
Tj=25℃(R
T
=6.2k,C
T
=1nF)
V
CC
=12V to 25V
T
A
= 0 to 70
℃
Peak to peak
T
J
=25℃
T
A
= 0 to 70
℃
V
PIN 1
=2.5V
V
FB
=5V
2V
≤
Vo
≤
4V
T
J
= 25℃
V
I
= 12V to 25V
V
PIN 2
= 2.7V, V
PIN 1
= 1.1V
V
PIN 2
= 2.3V, V
PIN 1
= 5V
V
PIN 2
= 2.3V, R
L
= 15kΩ to ground
V
PIN 2
= 2.7V, R
L
= 15kΩ to Pin 8
(note 3 & 4)
V
PIN 1
= 5V (note 3)
12V
≤
V
I
≤
25V
fosc
∆fosc/∆V
∆fosc/∆T
Vosc
I
dischg
V
2
Ib
BW
PSRR
I
O
I
O
2.50 2.58
-0.1 -2
90
-
1
-
70
-
12
-
-1
-
6.2
-
0.8 1.1
3 3.15
1
1.1
70
-
-2
-10
150 300
0.1
1.6
13.5
13.5
0.1
50
50
0.4
2.2
-
-
1.1
150
150
G
V
V
3
SVR
Ib
I
SINK
= 20mA
I
SINK
= 200mA
I
SOURCE
= 20mA
I
SOURCE
= 200mA
V
CC
= 6V, I
SINK
= 1mA
Tj=25℃, C
L
=1nF (note 2)
Tj=25℃, C
L
=1nF (note 2)
V
OL
V
OH
V
OLS
tr
tf
CYStek Product Specification
CYStech Electronics Corp.
Electrical Characteristics
(
continued
)
Parameter
Test Conditions
Symbol
Spec. No. : C510P8
Issued Date : 2003.04.24
Revised Date :
Page No. : 4/15
Min. Typ. Max.
14.5
7.8
8.5
7.0
94
47
-
16
8.4
10
7.6
96
48
-
0.3
0.3
12
36
17.5
9.0
11.5
8.2
100
50
0
0.5
0.5
17
-
Unit
V
V
V
Undervoltage Lockout Section
Start Threshold
PL3842B/PL3844B
Min Operating Voltage
After Turn-on
PWM Section
Maximum Duty Cycle
Minimum Duty Cycle
Total Standby Current
Start-up Current
Operating Supply Current
Zener Voltage
V
I
=6.5V for PL3843B/45B
V
I
=14V for PL3842B/44B
V
PIN 2
= V
PIN 3
= 0V
I
I
= 25 mA
I
I
V
IZ
Ist
PL3842B/PL3843B
PL3844B/PL3845B
PL3843B/PL3845B
PL3842B/PL3844B
PL3843B/PL3845B
%
%
%
mA
mA
mA
V
-
-
-
30
Notes: 1. Max. package power dissipation limits must be respected; low duty cycle pulse techniques are used during test
maintain Tj as close to Tamb as possible.
2.These parameters, although guaranteed, are not 100% tested in production.
3.Parameter measured at trip point of latch with V
PIN 2
= 0 .
4.Gain defined as:
A=
∆V
PIN 1
∆V
PIN 3
, 0
≤
V
PIN 3
≤
0.8V
5
.
Adjust V
I
above the start threshold before setting at 15V.
PL384XBP8
CYStek Product Specification
CYStech Electronics Corp.
Figure 1: Open Loop Test Circuit
Spec. No. : C510P8
Issued Date : 2003.04.24
Revised Date :
Page No. : 5/15
VREF
RT
4.7k
2N2222
A
VREF
100k
ERROR AMP.
ADJUST
COMP
VFB
1k
ISENSE
ADJUST
ISENSE
5k
RT/CT
0.1uF
VI
1
2
8
7
VI
0.1uF
1W
1k
OUTPUT
3
4
6
5
4.7k
OUTPUT
GROUND
CT
GROUND
High peak currents associated with capacitive loads necessitate careful grounding techniques. Timing and bypass
capacitors should be connected close to pin 5 in a single point ground. The transistor and 5kΩ potentiometer are
used to sample the oscillator waveform and apply an adjustable ramp to pin 3.
Figure 2:Timing Resistor vs Oscillator Frequency
100
CT=100pF
200pF
100
Figure 3:Output Dead-Time vs Oscillator Frequency
CT=2nF
Output Dead Time---(%)
CT=1nF
10
CT=500p
F
CT=200pF
CT=10nF
CT=5nF
Timing Resistor---RT(kΩ)
500pF
10
10nF
5nF
2nF
1nF
CT=100pF
Vi=15V
TA=25
1
1
10
Vi=15V,TA=25
℃
100
Oscillator Frequency---fosc(kHz)
1000
10
100
Oscillator Frequency---fosc(kHz)
1000
PL384XBP8
CYStek Product Specification
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