1
Features
+
-
+
-
V
REF
SYNC
Oscillator
Error
Amp 1
Error
Amp 2
Latching
PWM 2
Latching
PWM 1
V
REF
Undervoltage
Lockout
5.0V Ref
V
CC
Undervoltage
Lockout
V
CC
V
FB1
COMP
1
ENABLE
2
V
FB2
COMP
2
C
T
R
T
Gnd
Pwr Gnd
Sense
2
V
OUT2
Sense
1
V
OUT1
s
Oscillator has Precise
Duty Cycle
Limit and Frequency
Control
s
500kHz Current Mode
Operation
s
Automatic Feed Forward
Compensation
s
Separate Latching PWMs
for Cycle-By-Cycle
Current Limiting
s
Internally Trimmed
Reference with
Undervoltage Lockout
s
Switchable Second
Output
s
Two High Current Totem
Pole Outputs
s
Input Undervoltage
Lockout with Hysteresis
s
8.4V Start Up Voltage
Threshold
Package Options
16 Lead SO Wide
CS5661
High Performance Dual Channel
Current Mode Controller with ENABLE
1
SYNC
2
3
4
5
6
7
8
C
T
R
T
V
FB1
COMP
1
SENSE
1
V
OUT1
Gnd
16
15
14
13
12
11
10
9
V
CC
V
REF
ENABLE
2
V
FB2
COMP
2
SENSE
2
V
OUT2
Pwr Gnd
CS5661
Description
The CS5661 is a high performance,
fixed frequency, dual current mode
controller specifically designed for
Off-Line and DC to DC converter
applications. It offers the designer a
cost effective solution with minimal
external components. This integrat-
ed circuit features a unique oscilla-
tor for precise duty cycle limit and
frequency control, a temperature
compensated reference, two high
gain error amplifiers, two current
sensing comparators, and two high
current totem pole outputs ideally
suited for driving power MOSFETs.
V
OUT2
output is switchable via the
ENABLE
2
pin.
Also included are protective fea-
tures consisting of input and refer-
ence undervoltage lockouts, each
with hysteresis, cycle-by-cycle cur-
rent limiting, and a latch for single
pulse metering of each output.
The CS5661 is pin compatible with
the MC34065L.
Block Diagram
Rev. 2/2/99
Cherry Semiconductor Corporation
2000 South County Trail, East Greenwich, RI 02818
Tel: (401)885-3600 Fax: (401)885-5786
Email: info@cherry-semi.com
Web Site: www.cherry-semi.com
A Company
2
Electrical Characteristics:
(V
CC
= 15V, R
T
= 8.2k, C
T
= 3.3nF, for typical values T
A
= 25C, for min/max values -40C < T
A
< 85C,
unless otherwise stated.
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
Absolute Maximum Ratings
Output Current, Source or Sink (Note 1) ......................................................................................................................400mA
Output Energy (capacitive load per cycle) .......................................................................................................................5.0J
Current Sense, Enable and Voltage ......................................................................................................................-0.3 to +5.5V
Feedback Inputs
Sync Input High State (Voltage) ......................................................................................................................................5.5V
Low State (Reverse Current) ...................................................................................................................-5.0mA
Error Amp Output Sink Current......................................................................................................................................10mA
Storage Temperature Range ................................................................................................................................-65 to +150C
Operating Junction Temperature...................................................................................................................................+150C
Lead Temperature Soldering
Reflow (SMD styles only) ......................................................................................60 sec. max above 183C, 230C peak
ESD Capability (Human Body Model) ...................................................................................................................................2kV
CS5661
s
Reference Section
Reference Output Voltage,
I
OUT
= 1.0mA, T
J
= 25C
4.9
5.0
5.1
V
V
REF
Line Regulation
11V V
CC
15V
2.0
20.0
mV
Load Regulation
1.0mA I
OUT
10mA
3.0
30.0
mV
Total Output Variation over
4.85
5.15
V
Line, Load and Temperature
Output Short Circuit Current
30
100
mA
s
Oscillator and PWM Sections
Total Frequency Variation
11V V
CC
15V, T
low
T
A
T
high
46.0
49.5
53.0
kHz
over Line and Temperature
Frequency Change with
11V V
CC
15V
0.2
1.0
%
Voltage
Duty Cycle at each Output
Maximum
46.0
49.5
52.0
%
SYNC Current
High State V
IN
= 2.4V
170
250
A
Low State V
IN
= 0.8V
80
160
s
Error Amplifiers
Voltage Feedback Input
V
OUT
= 2.5V
2.42
2.50
2.58
V
Input Bias Current
V
FB
= 5.0V
-0.1
-1.0
A
Open-Loop Voltage Gain
2.0V V
OUT
4.0V
65
100
dB
Unity Gain Bandwidth
T
J
= 25C (Note 5)
0.7
1.0
MHz
Power Supply Rejection Ratio V
CC
= 11V to 15V
60
90
dB
Output Current
Source V
OUT
= 3.0V, V
FB
= 2.3V
-0.45
-1.00
mA
Sink V
OUT
= 1.2V, V
FB
= 2.7V
2.00
12.00
mA
Output Voltage Swing
High State R
L
= 15k to ground,
V
FB
= 2.3V
5.0
6.2
V
Low State R
L
= 15k to V
REF
,
V
FB
= 2.7V
0.8
1.1
V
3
CS5661
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
Note 1: Maximum package power dissipation limits must be observed.
Note 2: Low duty cycle pulse techniques are used during test to maintain
junction temperature as close to ambient as possible:
T
low
= -40C ; T
high
=+85C
Note 3: This parameter is measured at latch trip point with V
FB
=0V.
Note 4: Comparator gain is defined as:
AV=
Note 5: These parameters are guaranteed by design but not 100% tested
in production.
V Compensation
V Current Sense
s
Current Sense Section
Current Sense Input
(Notes 3 and 4)
2.75
3.00
3.25
V/V
Voltage Gain
Maximum Current Sense
(Note 3)
0.9
1.0
1.1
V
Input Threshold
Input Bias Current
-2.0
-30.0
A
Propagation Delay
Current Sense Input to Output (Note 5)
150
300
ns
s
Output 2 Enable Pin
Enable Pin Voltage
V
High State
OUTPUT
2
enabled
3.5
V
REF
V
Low State
OUTPUT
2
disabled
0.0
1.5
V
Low State Input Current
V
IL
= 0V
100
250
400
A
s
Drive Outputs
Output Voltage
Low State
I
SINK
= 20mA
0.1
0.4
V
I
SINK
= 200mA
1.6
2.5
V
High State
I
SOURCE
= 20mA
13.0
13.5
V
I
SOURCE
= 200mA
12.0
13.4
V
Output Voltage with
(V
CC
= 6.0V, I
SINK
= 1.0mA)
0.1
1.1
V
UVLO Activated
Output Voltage Rise Time
(C
L
= 1.0nF) Note 5
28
150
ns
Output Voltage Fall Time
(C
L
= 1.0nF) Note 5
25
150
ns
s
Undervoltage Lockout Section
Start-Up Threshold
7.4
8.4
9.4
V
Minimum Operating Voltage
After Turn-On
6.8
7.8
8.8
V
Hysteresis
0.6
V
s
Total Device
Start-Up Current
V
CC
= 6V
0.6
1.0
mA
Operating Current
20
25
mA
Electrical Characteristics:
(V
CC
= 15V, R
T
= 8.2k, C
T
= 3.3nF, for typical values T
A
= 25C, for min/max values -40C < T
A
< 85C,
unless otherwise stated.
4
CS5661
Package Pin Description
PACKAGE PIN #
PIN SYMBOL
FUNCTION
Typical Performance Characteristics
100pF
1.0nF
10k
30k
50k
100k
300k
500k
1.0M
f
OSC
OSCILLATOR FREQUENCY (Hz)
4.0
6.0
8.0
10
12
14
16
R
T
TIMING RESIST
OR (K
)
T
A
=25
C
2.2nF
3.3nF
5.0nF
C
T
=10nF
V
CC
=
15V
220pF
330pF
500pF
10k
30k
50k
100k
300k
500k
1.0M
f
OSC
OSCILLATOR FREQUENCY (Hz)
38
40
42
44
46
48
50
MAXIMUM DUTY
CYCLE (%)
V
CC
= 15V
R
T
= 4.0k
to 16k
C
L
= 15pF
T
A
= 25
C
Max. Output Duty Cycle vs. Oscillator Frequency
Timing Resistor vs. Oscillator Frequency
10k
100k
1.0k
10k
100k
1.0M
10M
f, FREQUENCY (Hz)
-20
0
20
40
60
80
100
A
VOL
, OPEN-LOOP
VOL
T
AGE GAIN (dB)
V
CC
= 15V
V
O
= 1.5V TO 2.5V
R
L
= 100k
T
A
= 25
C
GAIN
PHASE
180
150
120
90
60
30
0
Phase Margin (DEGREES)
0
1.0
2.0
3.0
4.0
5.0
7.0
ERROR AMP OUTPUT VOLTAGE (V)
0
0.2
0.4
0.6
0.8
1.0
1.2
Vth, CURRENT
SENSE
INPUT
THRESHHOLD
(V)
6.0
V
CC
= 15V
T
A
= 125
C
T
A
= 25
C
T
A
= -55
C
Current Sense Input Threshold
vs. Error Amp Output Voltage
Error Amp Open-Loop Gain & Phase vs. Frequency
16 Lead SO Wide
1
SYNC
A positive going pulse applied to this input will synchronize the
oscillator. A DC voltage within the range of 2.4V to 5.5V will
inhibit the oscillator.
2
C
T
Timing capacitor C
T
connects pin to ground setting oscillator
frequency.
3
R
T
Resistor R
T
connects to ground setting the charge current for C
T
.
Its value must be between 4.0k and 16k.
4
V
FB1
The inverting input of error amplifier 1. Normally it is connect-
ed to the switching power supply output.
5
COMP
1
The output of error amplifier 1, for loop compensation.
6
SENSE
1
Output 1 pulse by pulse current limit.
7
V
OUT1
Drives the power switch at output 1.
8
Gnd
Logic ground
9
Pwr Gnd
Power ground. Power device return is connected to this pin.
10
V
OUT2
Drives the power switch at output 2.
11
SENSE
2
Output 2 pulse by pulse current limit.
12
COMP
2
Output of error amplifier 2, for loop compensation.
13
V
FB2
Inverting input of error amplifier 2. Normally it is connected to
the switching power supply output.
14
ENABLE
2
Output 2 disable. A logic low at this pin disables V
OUT2
.
15
V
REF
5.0V reference output. It can source current in excess of 30mA.
16
V
CC
The positive supply of the IC. The minimum operating voltage
after start-up is 8.8V.
5
The CS5661 is a high performance, fixed frequency, dual
channel current mode PWM controller for Off-Line and
DC to DC converter applications. Each channel contains a
high gain error amplifier, current sensing comparator,
pulse width modulator latch, and totem pole output driv-
er. The oscillator, reference, and undervoltage lockout cir-
cuits are common to both channels.
The oscillator has both precise frequency and duty cycle
control. The oscillator frequency is programmed by the
timing components R
T
and C
T
. Capacitor C
T
is charged
and discharged by an equal magnitude internal current
source and sink that generates a symmetrical 50 percent
duty cycle waveform at C
T
. The oscillator peak and valley
thresholds are 3.5V and 1.6V respectively. The source/
sink current is controlled by resistor R
T
. For proper opera-
tion over temperature range R
T
's value should be between
4.0k to 16k.
As C
T
charges and discharges, an internal blanking pulse
is generated that alternately drives the inputs of the upper
and lower NOR gates high. This, in conjunction with a
precise amount of delay time introduced into each chan-
nel, produces well defined non-overlapping output duty
cycles. Output 2 is enabled while C
T
is charging, and
Output 1 is enabled during the discharge. Even at 500kHz,
each output is capable of approximately 44% duty cycle,
making this controller suitable for high frequency power
conversion applications.
In noise sensitive applications it may be necessary to syn-
chronize the converter with an external system clock. This
can be accomplished by applying an external clock signal.
For reliable synchronization, the oscillator frequency
should be set about 10% slower than the clock frequency.
The rising edge of the clock signal applied to SYNC, termi-
nates the charging of C
T
and V
OUT2
conduction. By tailor-
ing the clock waveform symmetry, accurate duty cycle
clamping of either output can be achieved.
Each channel contains a fully-compensated error amplifier
with access to the output and inverting input. The amplifi-
er features a typical dc voltage gain of 100 dB, and a unity
gain bandwidth of 1.0 MHz with 71 degrees of phase mar-
gin. The non-inverting input is internally biased at 2.5V.
The converter output voltage is typically divided down
and monitored by the inverting input through a resistor
divider. The maximum input bias current is -1.0 A which
will cause an output voltage error that is equal to the
product of the input bias current and the equivalent input
divider resistance.
Its output voltage is offset by two diode drops (1.4V) and
divided by three before it connects to the inverting input
of the current sense comparator. This guarantees that both
Operating Description
CS5661
Typical Performance Characteristics: continued
0
20
40
60
80
100
120
I
ref
, REFERENCE SOURCE CURRENT (mA)
-24
-20
-16
-12
-8.0
-4.0
0
V
REF
, REFERENCE
V
oltage (mV)
V
CC
= 15V
T
A
= 55
C
T
A
= 125
C
T
A
=
25
C
-55
-25
0
25
50
75
100
125
T
A
, AMBIENT TEMPERATURE (
C)
I
SC
, REFERENCE
SHOR
T
CIRCUIT
CURRENT
(mA)
120
100
80
60
Reference Short Circuit Current vs. Temperature
Reference Voltage Change vs. Source Current
SOURCE SATURATION
(LOAD TO GROUND)
V
CC
=15V
80
S PULSED LOAD
120Hz RATE
T
A
=25
C
T
A
= 55
C
T
A
= 55
C
T
A
=25
C
SINK
SATURATION
(LOAD TO V
CC
)
GND
0
200
400
600
800
OUTPUT LOAD CURRENT (mA)
V
sat
, OUTPUT
SA
TURA
TION VOL
T
AGE (V)
V
CC
0
-1.0
-2.0
2.0
1.0
0
8.4
V
CC,
SUPPLY VOLTAGE (V) - CS-5661
0
8.0
16
24
32
R
T
=8.2k
C
T
=3.3nF
V
FB
1, 2=0V
CURRENT SENSE 1, 2=0V
T
A
=25
C
I
CC,
SUPPL
Y
CURRENT
(mA)
Supply Current vs. Supply Voltage
Output Saturation Voltage vs. Load Current
Oscillator
Error Amplifier
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