MIC1555 Datasheet, PDF (1/8 Pages) Micrel Semiconductor – IttyBitty™ RC Timer / Oscillator

MIC1555/1557
Micrel
MIC1555/1557
IttyBitty™ RC Timer / Oscillator
General Description
The MIC1555 IttyBitty™ CMOS RC timer/oscillator and
MIC1557 IttyBitty CMOS RC oscillator are designed to pro-
vide rail-to-rail pulses for precise time delay or frequency
generation.
The devices are similar in function to the industry standard
“555”, without a frequency control (F_C) pin or an open-
collector discharge (D) pin. The threshold pin (TH) has
precedence over the trigger (TR) input, ensuring that the
BiCMOS output is off when TR is high.
The MIC1555 may be used as an astable (oscillator) or
monostable (one-shot) with separate threshold and trigger
inputs. In the one-shot mode, the output pulse width is
precisely controlled by an external resistor and a capacitor.
Time delays may be accurately controlled from microsec-
onds to hours. In the oscillator mode, the output is used to
provide precise feedback, with a minimum of one resistor and
one capacitor producing a 50% duty cycle square wave.
The MIC1557 is designed for astable (oscillator) operation
only, with a chip select/reset (CS) input for low power shut-
down. One resistor and one capacitor provide a 50% duty
cycle square wave. Other duty-cycle ratios may be produced
using two diodes and two resistors.
The MIC1555/7 is powered from a +2.7V to +18V supply
voltage.
The MIC1555/7 is available in the SOT-23-5 5-lead package,
and is rated for –40°C to +85°C ambient temperature range.
Features
• +2.7V to +18V operation
• Low current
<1µA typical shutdown mode (MIC1557)
200µA typical (TRG and THR low) at 3V supply
• Timing from microseconds to hours
• “Zero” leakage trigger and threshold inputs
• 50% square wave with one Resistor, one Capacitor
• Threshold input precedence over trigger input
• <15Ω output on resistance
• No output cross-conduction current spikes
• <0.005%/°C temperature stability
• <0.055%/V supply stability
• Small SOT-23-5 surface mount package
Applications
• Precision timer
• Pulse generation
• Sequential timing
• Time-delay generation
• Missing pulse detector
• Micropower oscillator to 5MHz
• Charge-pump driver
• LED blinker
• Voltage converter
• Linear sweep generator
• Variable frequency and duty cycle oscillator
• Isolated feedback for power supplies
Ordering Information
Part Number
MIC1555BM5
MIC1557BM5
Temp. Range
–40°C to +85°C
–40°C to +85°C
Package
SOT-23-5
SOT-23-5
Marking
T10
T11
Typical Applications
Standby
Trigger
+5V
100µs
MIC1555
1 _VS
OUT ³
Output
4
TRG
1k
2 _{GND THR} 5
0.1µF
Monostable (One-Shot)
October 1998
Enabled
Disabled
+5V
8kHz
MIC1557
4 _VS
OUT ⁵
Output
3 _CS
1k
2 _GND
T/T ¹
0.1µF
Astable (Oscillator)
1
MIC1555/1557