MIC1555YM5 TR Micrel Inc, MIC1555YM5 TR Datasheet - Page 6

• Manufacturer Part Number: MIC1555YM5 TR
• Description: IC RC TIMER/OSCILLATOR SOT23-5
• Manufacturer: Micrel Inc
• Type: 555 Type, Timer/Oscillator (Single)r
• Series: IttyBitty®r

Specifications of MIC1555YM5 TR

• Frequency: 5MHz
• Voltage - Supply: 2.7 V ~ 18 V
• Current - Supply: 350µA
• Operating Temperature: -40°C ~ 85°C
• Package / Case: SOT-23-5, SC-74A, SOT-25
• # Internal Timers: 1
• Operating Supply Voltage (min): 2.7V
• Operating Supply Voltage (typ): 3.3/5/9/12/15V
• Operating Supply Voltage (max): 18V
• Package Type: SOT-23
• High Level Output Current: -20mA
• Low Level Output Current: 20mA
• Pin Count: 5
• Operating Temp Range: -40C to 85C
• Operating Temperature Classification: Industrial
• Mounting: Surface Mount
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Count: -
• Lead Free Status / Rohs Status: Compliant
• Other names: 576-2576-2; MIC1555YM5 TR; MIC1555YM5TR; MIC1555YM5TR

Functional Description
Refer to the block diagrams.
The MIC1555/7 provides the logic for creating simple RC
timer or oscillator circuits.
The MIC1555 has separate THR (threshold) and TRG
(trigger) connections for monostable (one-shot) or
astable (oscillator) operation.
The MIC1557 has a single T/T (threshold and trigger)
connection for astable (oscillator) operation only. The
MIC1557 includes a CS (chip select/reset) control.
Supply
VS (supply) is rated for +2.7V to +18V. An external
capacitor is recommended to decouple noise.
Resistive Divider
The resistive voltage divider is constructed of three
equal value resistors to produce 1/3V
for trigger and threshold reference voltages.
Chip Select/Reset (MIC1557 only)
CS (chip select/reset) controls the bias supply to the
oscillator’s internal circuitry. CS must be connected to
CMOS logic-high or logic-low levels. Floating CS will
result in unpredictable operation. When the chip is
deselected, the supply current is less than 1µA. Forcing
CS low resets the MIC1557 by setting the flip flop,
forcing the output low.
Threshold Comparator
The threshold comparator is connected to S (set) on the
RS flip-flop. When the threshold voltage (2/3V
reached, the flip-flop is set, making the output low. THR
is dominant over TRG.
Micrel, Inc.
May 2010
S
and 2/3V
S
voltage
S
) is
6
Trigger Comparator
The trigger comparator is connected to R (reset) on the
RS flip-flop. When TRG (trigger) goes below the trigger
voltage (1/3V
high.
Flip-Flop and Output
A reset signal causes Q to go low, turning on the P-
channel MOSFET and turning off the N-channel
MOSFET. This makes the output rise to nearly V
A set signal causes Q to go high, turning off the P-
channel MOSFET, and turning on the N-channel
MOSFET, grounding OUT.
Basic Monostable Operation
Refer to the MIC1555 functional diagram.
A momentary low signal applied to TRG causes the
output to go high. The external capacitor charges slowly
through the external resistor. When VTHR (threshold
voltage) reaches 2/3V
discharging the capacitor. During power-on, a single
pulse may be generated.
Basic Astable Operation
Refer to the MIC1557 functional diagram.
The MIC1557 starts with T/T low, causing the output to
go high. The external capacitor charges slowly through
the external resistor. When VT/T reaches 2/3V
(threshold voltage), the output is switched off, slowly
discharging the capacitor. When VT/T decreases to
1/3V
causing VT/T to rise again, repeating the cycle.
S
(trigger voltage), the output is switched on,
S
), the flip-flop resets, making the output
S
, the output is switched off,
M9999-052610-D
MIC1555/1557
S
.
S