IP1844A 查看數據表（PDF） - Semelab - > TT Electronics plc
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IP1844A Datasheet PDF : 6 Pages
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SEME
LAB
IP1844A SERIES
IP1845A SERIES
V REF 8
RTCT 4
GND 5
APPLICATIONS INFORMATION
Oscillator Waveforms and Maximum Duty Cycle
LARGE RT
SMALL CT
VPIN4 (VPIN7 for 14 pin D package)
INTERNAL CLOCK
RT
LARGE CT
CT
SMALL RT
OUTPUT – Max. Duty Cycle
VPIN6 (VPIN10 for 14 pin D package)
VPIN4 (VPIN7 for 14 pin D package)
INTERNAL CLOCK
OUTPUT – Max. Duty Cycle
VPIN6 (VPIN10 for 14 pin D package)
Oscillator timing capacitor CT is charged by VREF tc ≈ 0.55 RTCT
( ) through RT and discharged by an internal current source.
During the discharge time, the internal clock signal
blanks the output to the low state. Selection of RT and
CT therefore determines both oscillator frequency and
maximum duty cycle. Charge and discharge times are
td ≈ RTCT Rn
.0063 RT – 2.3
.0063 – 4
Resultant frequency
f
=
(tc
1
+
td)
determined by the formulae:
For RT > 5kΩ,
Resultant frequency
f≈
1.8
(RTCT)
Open–Loop Laboratory Test Fixture
4.7k Ω
1k Ω
ERROR AMP
ADJUST
4.7k Ω
2N2222
100k Ω
5k Ω
ISENSE
ADJUST
RT
1 COMP
2 VFB
3 ISENSE
4 R T /C T
VREF 8
VCC 7
O/P 6
0.1
µF
0.1
µF 1k Ω
1kW
GND 5
VREF
VCC
OUTPUT
GROUND
CT
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.
Semelab plc. Telephone (01455) 556565. Telex: 341927. Fax (01455) 552612.
Prelim. 2/95
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