Page 1
LAB
SEME
IP1844A SERIES
IP1845A SERIES
Semelab plc. Telephone (01455) 556565. Telex: 341927. Fax (01455) 552612.
Prelim. 2/95
TOP VIEW
J Package – 8 Pin Ceramic DIP
N Package – 8 Pin Plastic DIP
D-8 Package – 8 Pin Plastic (150) SOIC
1
2
3
4
8
7
6
5
COMP
V
REF
GROUND
OUTPUT
RT/C
T
V
CC
I
SENSE
V
FB
TOP VIEW
D-14 Package – 14 Pin Plastic (150) SOIC
COMP
V
REF
GROUND
OUTPUT
1
2
3
4
POWER
GROUND
5
6
7
14
13
12
11
10
9
8
N/C
R
T/CT
I
SENSE
N/C
N/C N/C
V
CC
V
FB
V
C
CURRENT MODE
REGULATING
PULSE WIDTH
MODULATORS
FEATURES
• Guaranteed ±1% reference voltage tolerance
• Accurate oscillator discharge current
• Guaranteed ±10% frequency tolerance
• Low start–up current (<500 mA)
• Under voltage lockout with hysteresis
• Output state completely defined for all supply
and input conditions
• Interchangeable with IP and UC1844/5 series for
improved operation
• 500kHz Oscillator operation
250kHz Output operation
+30V
Self limiting
±1A
5µJ
–0.3V to +V
CC
10mA
1W
10mW/°C
725mW
7.25mW/°C
2W
16mW/°C
–65 to 150°C
+300°C
ABSOLUTE MAXIMUM RATINGS (T
case
= 25°C unless otherwise stated)
V
CC
Supply Voltage (low impedance source)
(ICC< 30mA)
I
O
Output Current
Output Energy (capacitive load)
Analog Inputs (pins 2 and 3)
Error Amp Output Sink Current
P
D
Power Dissipation T
amb
= 25°C J, N Packages
Derate @ T
amb
> 50°C
P
D
Power Dissipation T
case
= 25°C D Package
Derate @ T
amb
> 50°C
P
D
Power Dissipation T
case
= 25°C J, N Packages
Derate @ T
case
> 25°C
T
STG
Storage Temperature Range
T
L
Lead Temperature (soldering, 10 seconds)
Part J–Pack N–Pack D–8 D–14 Temp.
Number 8 Pin 8 Pin 8 Pin 14 Pin Range
IP1844A ✔ -55 to +125°C
IP2844A ✔✔✔✔-25 to +85°C
IP3844A ✔✔✔✔0 to +70°C
IP1845A ✔ -55 to +125°C
IP2845A ✔✔✔✔-25 to +85°C
IP3845A ✔✔✔✔0 to +70°C
Order Information
Note:
To order, add the package identifier to the
part number.
eg. IP1844AD–14
IP3845AJ
Page 2
LAB
SEME
IP1844A SERIES
IP1845A SERIES
Semelab plc. Telephone (01455) 556565. Telex: 341927. Fax (01455) 552612.
Prelim. 2/95
V
CC
Supply Voltage
1
I
O
Output Current
Analog Inputs (pins 2 and 3)
Error Amp Output Sink Current
IP1844A , IP1845A
Operating Ambient Temperature Range IP2844A , IP2845A
IP3844A , IP3845A
≤ 30V
0 to ±200mA
–0.3V to 3V
0 to 2mA
–55 to 125°C
–25 to 85°C
0 to 70°C
Notes:
1. Lower limit set by under voltage lockout specification.
RECOMMENDED OPERATING CONDITIONS
* 1844A and 1845A series only.
Values in brackets are for IP1845 series.
3.6V
ERROR
AMP
OSCILLATOR
2R
R
1V
R
S
PWM
LATCH
CURRENT
SENSE
COMPARATOR
16V
(8.4V)
6V
(0.5V) 2.5V
UNDER–VOLTAGE
LOCKOUT
ENABLE
REFERENCE
REGULATOR
5V
INTERNAL
BIAS
34V
REG
R
S
V STATUS
LATCH
REF
PIN NUMBERS
1st Number
2nd Number
– N, J and 8 Pin D Packag es
– 14 Pin D Package.
C
OMP
G
ND
V
CC
I
SENSE
V
FB
/CR
TT
OUTPUT
POWER
GROUND
V
REF
V
C
3/5
5/9
7/12
2/3
1/1
4/7 6/10
7/11
5/8
8/14
TOGGLE
FLIP
FLOP *
T
Q
DESCRIPTION
The IP1844A/IP1845A series of switching regulator control circuits contain all the functions necessary to
implement off-line, current mode switching regulators, using a minimum number of external parts. Functions
included are voltage reference, error amplifier, current sense comparator, oscillator, totem-pole output driver and
under-voltage lockout circuitry.
In addition the IP1844A and IP1845A series of devices have a toggle flip-flop which blanks the output on every
second clock pulse, thereby ensuring that the duty cycle never exceeds 50%. For applications requiring more
flexible control, all devices feature an on-chip trimmed oscillator discharge current, allowing accurate control to
maximum-duty-cycle by selection of timing components. This can be beneficial even when using the IP1844A or
IP1845A series, as it allows optimum safety margins to be designed into the application.
Although pin compatible with the standard IP1844/5 parts these devices offer improved performance in several
areas. They also offer tighter specification and improved performance over the IP and UC1844/5 series, whilst
retaining complete compatibility.
BLOCK DIAGRAM
Page 3
LAB
SEME
IP1844A SERIES
IP1845A SERIES
Semelab plc. Telephone (01455) 556565. Telex: 341927. Fax (01455) 552612.
Prelim. 2/95
NOTES
1. Test Conditions unless otherwise stated:
V
CC
= 15V* , RT= 10kΩ , CT= 3.3nF , f = 52kHz.
*Adjust V
CC
above start threshold before setting at required level.
2. Output frequency is half the oscillator frequency.
4.90 5.00 5.10
620
625
0.2 0.4
4.82 5.18
50
525
30 80 160
47 52 57
0.2 1
5
1.7
7.8 8.3 8.8
79
2.42 2.50 2.58
–0.3 –2
65 90
0.7 1
60 70
26
–0.5 –0.8
56
0.7 1.1
4.95 5.00 5.05
620
625
0.2 0.4
4.90 5.10
50
525
30 80 160
47 52 57
0.2 1
5
1.7
7.8 8.3 8.8
79
2.45 2.50 2.55
–0.3 –1
65 90
0.7 1
60 70
26
–0.5 –0.8
56
0.7 1.1
IP1844A , IP1845A IP3844A
IP2844A , IP2845A IP3845A
Parameter Test Conditions
1
Min. Typ. Max. Min. Typ. Max. Units
Output Voltage
Input Regulation
Output Regulation
Temperature Stability
Total Output Variation
Output Noise Voltage
Long Term Stability
Output Short Circuit
Current
Frequency
Voltage Stability
Temperature Stability
Amplitude
Discharge Current
Input Voltage
Input Bias Current
Open Loop Voltage
Gain
Unity Gain Bandwidth
Supply Voltage
Rejection
Output Sink Current
Output Source Current
V
OUT
High
V
OUT
Low
I
O
= 1mA TJ= 25°C
V
CC
= 12V to 25V
I
O
= 1mA to 20mA
Line, Load, Temp
f = 10Hz to 10kHz T
J
= 25°C
T
J
= 125°C @ 1000Hrs
V
REF
= 0
T
J
= 25°C (Note 2)
V
CC
= 12V to 25V
∆T
A
= Min to Max
V
PIN4
Peak to Peak
T
J
= 25°C
∆T
A
= Min to Max
V
PIN1
= 2.5V
V
O
= 2V to 4V
V
CC
= 12V to 25V
V
PIN2
= 2.7V V
PIN1
= 1.1V
V
PIN2
= 2.3V V
PIN1
= 5V
V
PIN2
= 2.3V RL= 15kΩ
V
PIN2
= 2.7V RL= 15kΩ
V
mV
mV
°C
V
µV
mV
mA
kHz
%
%
V
mA
V
µA
dB
MHz
dB
mA
V
ELECTRICAL CHARACTERISTICS (Over Full Operating Temperature Range unless otherwise stated)
REFERENCE SECTION
OSCILLATOR SECTION
ERROR AMP SECTION
All specifications apply over the full operating temperature range unless otherwise stated.
(See Ordering Information for further details).
Page 4
LAB
SEME
IP1844A SERIES
IP1845A SERIES
Semelab plc. Telephone (01455) 556565. Telex: 341927. Fax (01455) 552612.
Prelim. 2/95
IP1844A , IP1845A IP3844A
IP2844A , IP2845A IP3845A
Parameter Test Conditions
1
Min. Typ. Max. Min. Typ. Max. Units
2.85 3 3.15
0.9 1 1.1
60 70
–2 –10
150 300
0.1 0.4
1.5 2.2
13 13.5
12 13.5
50 150
50 150
0.7 1.1
14.5 16 17.5
7.8 8.4 9
8.5 10 11.5
7 7.6 8.2
0.3 0.5
11 15
14 17
30 34 40
46 48 50
0
2.85 3 3.15
0.9 1 1.1
60 70
–2 –10
150 300
0.1 0.4
1.5 2.2
13 13.5
12 13.5
50 150
50 150
0.7 1.1
15 16 17
7.8 8.4 9
91011
7 7.6 8.2
0.3 0.5
11 15
14 17
30 34 40
47 48 50
0
Gain
Maximum Input Signal
Supply Voltage
Rejection
Input Bias Current
Delay to Output
Output Low Level
Output High Level
Rise Time
Fall Time
UVLO Saturation
Upper Threshold
(V
CC
)
Lower Threshold
(V
CC
)
Start–up Current
Operating Supply
Current
V
CC
Zener Voltage
Maximum Duty Cycle
Minimum Duty Cycle
See Notes 2,3
V
PIN1
= 5V (Note 2)
V
C
= 12V to 25V
I
SINK
= 20mA
I
SINK
= 200mA
I
SOURCE
= 20mA
I
SOURCE
= 200mA
C
L
= 1nF
C
L
= 1nF
V
CC
= 6V IL= 1mA
IP1844A Series
IP1845A Series
IP1844A Series
IP1845A Series
V
PIN2
= 0V IP1844A Series
V
PIN3
= 0V IP1845A Series
I
CC
= 25mA
V/V
V
dB
µA
ns
V
V
ns
V
V
V
mA
mA
V
%
NOTES
ELECTRICAL CHARACTERISTICS (Over Full Operating Temperature Range unless otherwise stated)
CURRENT SENSE SECTION
OUTPUT SECTION
UNDER–VOLTAGE LOCKOUT SECTION
TOTAL STANDBY CURRENT
PWM SECTION
1. Test Conditions unless otherwise stated:
V
CC
= 15V* , RT= 10kΩ , CT= 3.3nF , f = 52kHz.
*Adjust V
CC
above start threshold before setting at
required level.
All specifications apply over the full operating temperature
range unless otherwise stated.
(See Ordering Information for further details).
2. Parameter measured at trip point of latch with
V
PIN2
= 0V
3. Gain defined as:
∆V
PIN1
A =
∆V
PIN3
0 ≤ V
PIN3
≤ 0.8
Page 5
For RT> 5kΩ,
1.8
Resultant frequency f ≈
(R
TCT
)
.0063 R
T
– 2.3
.0063 – 4
( )
tc≈ 0.55 RTC
T
td≈ RTC
T
Rn
1
Resultant frequency f =
(t
c
+ td)
Oscillator timing capacitor CTis charged by V
REF
through RTand discharged by an internal current source.
During the discharge time, the internal clock signal
blanks the output to the low state. Selection of R
T
and
C
T
therefore determines both oscillator frequency and
maximum duty cycle. Charge and discharge times are
determined by the formulae:
LAB
SEME
IP1844A SERIES
IP1845A SERIES
Semelab plc. Telephone (01455) 556565. Telex: 341927. Fax (01455) 552612.
Prelim. 2/95
Open–Loop Laboratory Test Fixture
APPLICATIONS INFORMATION
High peak current 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 5K potentiometer are used to sample the oscillator wave
form and apply an adjustable ramp to pin 3.
0.1
µ
F
1k
Ω
1kW
1k
Ω
ERROR AMP
ADJUST
4.7k
Ω
5k
Ω
ADJUST
4.7k
Ω
100k
Ω
2N2222
I
SENSE
R
T
C
T
0.1
µ
F
V
REF
V
CC
OUTPUT
GROUND
1
2
45
7
8
36
I
SENSE
V
REF
V
CC
O/P
GND
COMP
V
FB
RT/C
T
Oscillator Waveforms and Maximum Duty Cycle
8
4
5
GND
R
T
C
T
REF
V
R
TCT
PIN4
V (V for 14 pin D package)
PIN7
INTERNAL CLOCK
INTERNAL CLOCK
OUTPUT – Max. Duty Cycle
PIN6
V (V for 14 pin D package)
PIN10
PIN4
V (V for 14 pin D package)
PIN7
OUTPUT – Max. Duty Cycle
PIN6
V (V for 14 pin D package)
PIN10
LARGE C
T
SMALL R
T
LARGE R
T
SMALL C
T
Page 6
LAB
SEME
IP1844A SERIES
IP1845A SERIES
Semelab plc. Telephone (01455) 556565. Telex: 341927. Fax (01455) 552612.
Prelim. 2/95
.01 .0 2 .04 .07 .1 .2 .4 .7 1.0
4
3
2
1
0
60
40
20
0
100
80
10 1k100 10k 10M100k 1M
.05 .5.03 .3
OUTPUT CURRENT, SOURCE / SINK (A) FREQUENCY (Hz)
SATURATION VOLTAGE (V)
VOLTAGE GAIN (dB)
OUTPUT SATURATION CHARACTERISTICS
ERROR AMPLIFIER OPEN-LOOP
FREQUENCY RESPONSE
V = 15V
CC
T = 25˚C
A
A
V
f
SOURCE SAT V - )CCV
OH
SINK SAT (V )
OL
(
A
T = –55˚C
–45
–90
–135
–180
0
PHASE (˚)
TYPICAL PERFORMANCE CHARACTERISTICS
0
20
15
10
0.5
0
10515200
0
52.5 7.5 10
UNDER VOLTAGE LOCKOUT
1844A SERIES
UNDER VOLTAGE LOCKOUT
1845A SERIES
V (V)
CC
V (V)
CC
I (m A)
CC
20
15
10
0.5
I (mA)
CC
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