ST1843
ST1845
Rad-tolerant current mode PWM controller
Features
■
■
■
■
■
■
■
■
■
■
■
Oscillator frequency guaranteed at 250 kHz
Trimmed oscillator for precise frequency
control
Current mode operation to 500 kHz 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
Hermetic package
50 and 100 krad (Si)
SEL free @ 120 MeV/cm2/mg at 125°C
Flat-8
Description
The ST1843HR and ST1845HR ICs are rad-
tolerant current mode PWM controllers providing
an industry standard solution for the
implementation of provides the off-line or DC to
DC fixed frequency current mode control
schemes with a minimal external parts count.
Its radiation hardness and hermetic packaging
makes it an ideal choice for aerospace and other
harsh environments.
Table 1.
Device summary
Quality level
Engineering Model
EPPL Package Lead finish Mass (g)
-
Flat-8
Flat-8
Flat-8
Flat-8
Gold
Gold
Gold
Gold
0.45
0.45
0.45
0.45
Order codes Duty cycle max Radiation level
ST1843K1
ST1843FKG
ST1845K1
ST1845RKG
100%
100%
50%
50%
50 krad (Si)
50 krad (Si)
100 krad (Si)
100 krad (Si)
According to ESCC Target
Engineering Model
-
According to ESCC Target
September 2011
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Contents
ST1843 - ST1845
Contents
1
2
3
4
5
6
Block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Thermal data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Pin connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Radiation characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
6.1
Total dose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
6.1.1
6.1.2
6.1.3
Bias conditions and total dose level for total dose radiation testing . . . . . 9
Electrical measurements for total dose radiation testing . . . . . . . . . . . . 10
Heavy Ions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
7
8
9
10
Test circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Ordering information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
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Doc ID 019049 Rev 1
ST1843 - ST1845
Block diagram
1
Block diagram
Figure 1.
Block diagram (toggle flip flop used only in UC3844B and UC3845B)
Doc ID 019049 Rev 1
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Maximum ratings
ST1843 - ST1845
2
Maximum ratings
Table 2.
Symbol
V
i
I
O
E
O
Absolute maximum ratings
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
Value
30
Self limiting
±1
5
–
0.3 to 5.5
10
800
–
65 to 150
–
40 to 150
A
mJ
V
mA
mW
°C
°C
Unit
V
P
tot
T
stg
T
J
Power dissipation at T
A
≤
25 °C (SO8)
Storage temperature range
Junction operating temperature
Note:
All voltages are with respect to pin 5, all currents are positive into the specified terminal.
3
Thermal data
Table 3.
Symbol
R
thJA
Thermal data
Description
Thermal resistance Junction-ambient. max.
Flat-8
100
Unit
°C/W
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Doc ID 019049 Rev 1
ST1843 - ST1845
Pin connection
4
Pin connection
Figure 2.
Pin connection
Table 4.
No
1
2
3
Pin functions
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 RT to Vref and capacitor CT to ground. Operation to 500 kHz is
possible.
Function
COMP
V
FB
I
SENSE
4
5
6
7
8
R
T
/C
T
GROUND This pin is the combined control circuitry and power ground.
OUTPUT
V
CC
V
ref
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 CT through
resistor RT.
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