Primary Side PWM Controller
Features
Description
The AS2214 is a full featured, pulse width modulation
controller. Based on an improved AS3842, the AS2214
provides additional features that reduce component count
and improve specifications in a wide range of power supply
designs. The added functionality includes AC power and
bulk voltage sensing, over-voltage input, as well as the ability
to latch off or bounce through different fault conditions.
The PWM function is controlled by the current sense com-
parator for normal current mode control and a second
comparator for voltage mode soft start. A buffered RAMP
signal is available for slope compensation without loading
the oscillator. The output stage is a high current totem pole
output that sees only 85 ns delay from the PWM comparator.
The AS2214 requires less than 10µA of startup current. The
undervoltage lockout (UVLO) thresholds are nominally 13.8V
for turn on and 8 V for turn off. A precision 2.5 V bandgap
reference serves as an input for the error amplifier. The
oscillator discharge current is trimmed to provide guaran-
teed duty cycle clamping.
AS2214
•
•
•
•
•
•
•
•
•
Low Startup Current
Bulk and AC sensing
Soft Start
Single-start or auto-restart
modes
Oscillator trimmed for precision
duty cycle clamp
Standard temperature range
extended to 105°C
Remote on / off control
Buffered Ramp for slope
compensation
Standard current mode control
Pin Configuration
—
Top view
V
CC
V
REG
COMP
V
FB
ISNS
SS
RAMP
1
2
3
4
5
6
7
14 OUT
13 GND
12 BOK
11 LEN
10 ACP
9
8
OV
RT/CT
Ordering Information
Package
Temperature Range
Order Code
14-Pin Plastic DIP
0 to 105° C
AS2214N
ASTEC Semiconductor
83
AS2214
Functional Block Diagram
Primary Side PWM Controller
V
CC
A CP
AC
DETECT
(LEN)
V
REG
6V
5V enab le
5V Reg.
V
REG
LEN
50µA
UV LO
V
REG
BOK
2V 5
(BULK_UV )
6µA
(CLR)
3V 95
OV
(OV )
2V 5
ISNS
COMP
SS LOGIC
(RUN)
SS
V
FB
2V 5
2R
CM PWM
V
CC
1V
R
(PWM)
OUT
SS PWM
OSC
(BLA NK)
RT/CT
GND
RA MP
x1
ASTEC Semiconductor
84
ENABL
0
1
1
1
1
0
1
Latch_bias
0
0
1
0
V REG
0
0
0
1
2V7
-
1
1
0
0
-
1
0
1
0
6µA
-
0
1
0
1
V REG
-
0
0
Q
•Q
-
-
-
0
0
AS2214 Soft Start Logic
Primary Side PWM Controller
ASTEC Semiconductor
Preset
S
R
Q
•Q
LEN
ENBL
OV
S
Q
•Q
S
R
ENBL
S
Q
•Q
ENBL
S
Q
•Q
R
PRESET
VOV
R
Started
R
VREG
PRESET
Faulted
ENBL
Q
•Q
PRESET
2V5
SS
85
PRESET
OV
1V7
3V9
BOK
PWM_Disable
AS2214
2V5
AS2214
Pin Function Description
Pin Number
Function
Primary Side PWM Controller
Description
1
2
3
4
5
6
V
CC
V
REG
COMP
V
FB
ISNS
SS
Positive supply voltage for the IC.
Output of 5V series regulator.
This pin is the error amplifier output. Typically used to provide loop compensation to
maintain V
FB
at 2.5 V.
Inverting input of the error amplifier. The non-inverting input is a trimmed 2.5 V
bandgap reference.
A voltage proportional to inductor current is connected to this pin. The PWM uses this
information to terminate the gate drive of the output.
This pin provides a 6µA current source to linearly charge an external capacitor. This pin
is compared to the RAMP pin in the soft start comparator, terminating output pulses when
RAMP goes above the SS voltage.
This pin is a level-shifted and buffered oscillator signal used to provide slope compensa-
tion to the current sense signal. The pin also serves as the non-inverting input of the soft-
start comparator.
Oscillator frequency and maximum duty cycle are set by connecting a resistor (R
T
) to
VREG and a capacitor (C
T
) to ground.
This pin latches SS low when pulled above 2.5 V. The latch can be reset by pulling
OV above 4 V then back to ground.
This pin detects the presence of AC signal and drives LEN high.
This pin must be high to enable starting. The pin can also clear all latches by going low
then high.
This pin monitors the bulk voltage through a resistor divider and, when BOK exceeds
2.5 V, provides a 50µA current source for hysteresis. When BOK drops below 2.5V, SS
is pulled low and the hysteresis current is turned off. Auto-restart after a brown-out is
possible.
Circuit common ground.
This totem pole output is designed to directly drive a power MOSFET switch capable of
sourcing and sinking peak currents up to 1 A.
7
RAMP
8
9
10
11
12
RT/CT
OV
ACP
LEN
BOK
13
14
GND
OUT
ASTEC Semiconductor
86
Primary Side PWM Controller
Absolute Maximum Ratings
Parameter
Symbol
Rating
AS2214
Unit
Reference Current
Output Current
Supply Voltage
Output Voltage
Continuous Power Dissipation at 25° C
Junction Temperature
Storage Temperature Range
Lead Temperature, Soldering 10 Seconds
I
REF
I
OUT
V
CC
V
OUT
P
D
T
J
T
STG
T
L
200
1
20
20
500
150
– 65 to 150
300
mA
A
V
V
mW
°C
°C
°C
Stresses greater than those listed under ABSOLUTE MAXIMUM RATINGS may cause permanent damage to the device. This is a stress
rating only and functional operation of the device at these or any other conditions above indicated in the operational sections of this
specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect reliability.
Recommended Conditions
Parameter
Supply Voltage
Oscillator
Symbol
V
CC
F
OSC
Rating
10 - 15
50 - 250
Unit
V
kHz
Typical Thermal Resistance
Package
14L PDIP
θ
JA
85° C/W
θ
JC
40° C/W
Typical Derating
11.7 mW/°C
Electrical Characteristics
Electrical Characteristics are guaranteed over full junction temperature range (0 to 105° C). Ambient temperature must be derated
based on power dissipation and package thermal characteristics. Unless otherwise specified, the conditions of test are V
CC
= 15 V;
BOK = 3 V; OV = 0V; R
T
= 680
Ω;
C
T
= 10 nF. To override UVLO, V
CC
should be raised above 18 V prior to test.
Parameter
Error Amplifier
Input Voltage
Input Bias Current
Voltage Gain
Transconductance
Unity Gain Bandwidth
Power Supply Rejection Ratio
Output Sink Current
Output Source Current
Output Swing High
Output Swing Low
V
FB
I
BIAS
A
VOL
G
m
GBW
PSRR
I
COMPL
I
COMPH
I
COMPH
I
COMPL
12
≤
V
CC
≤
18 V
V
FB
= 2.7 V; V
COMP
= 1.1 V
V
FB
= 2.3 V; V
COMP
= 5 V
V
FB
= 2.3 V; R
L
= 15
Ω
to GND
V
FB
= 2.7 V; R
L
= 15
Ω
to V
REG
0.8
60
2
0.5
5
2
≤
V
COMP
≤
4 V
65
T
J
= 25°C
2.465
2.500
-0.1
90
1
1.2
70
6
1.0
5.5
0.7
1.1
2.535
-1
V
µA
dB
mA/mV
MHz
dB
mA
mA
V
V
Symbol
Test Condition
Min
Typ
Max
Unit
ASTEC Semiconductor
87
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