Micrel, Inc.
Notes:
1. Exceeding the absolute maximum rating may damage the device.
2. The device is not guaranteed to function outside its operating rating.
3. Devices are ESD sensitive. Handling precautions recommended.
4. P
D(max)
= (T
J(max)
– T
A
) ÷
θ
JC
. Exceeding T
J(max)
will cause thermal shutdown.
MIC2954
5. Thermal resistance (θ
JC
) of the TO-220 package is 2.5°C/W, and 15°C/W for the SOT-223. Thermal resistance (θ
JC
) of the TO-92 package is
180°C/W with 0.4" leads and 160°C/W with 0.25" leads. Thermal resistance (θ
JA
) of the SOP-8 is 160°C/W mounted on a printed circuit board
(See “Application Information: Thermal Calculation”).
6. Output voltage temperature coefficient is defined as the worst case voltage change divide by the total temperature range.
7. Line regulation for the MIC2954 is tested at 125°C for I
L
= 1mA. For I
L
= 100µA and T
J
= 125°C, line regulation is guaranteed by design to0.2%.
See “Typical Characteristics” for line regulation versus temperature and load current.
8. Regulation is measured at constant junction temperature using low duty cycle pulse testing. Changes in output voltage due to heating effects are
covered by the thermal regulation specification.
9. Dropout Voltage is defined as the input to output differential at which the output voltage drops 100 mV below its nominal value measured at 1V
differential. At very low values of programmed output voltage, the minimum input supply voltage of 2 V (2.3V over temperature) must be taken into
account.
10. Ground pin current is the regulator quiescent current. The total current drawn from the source is the sum of the load current plus the ground pin
current.
11. The MIC2954 features fold-back current limiting. The short circuit (V
OUT
= 0V) current limit is less than the maximum current with normal output
voltage.
12. Thermal regulation is defined as the change in output voltage at a time t after a change in power dissipation is applied, excluding load or line
regulation effects. Specifications are for a 200mA load pulse at V
IN
= 20V (a 4W pulse) for t = 10ms.
13. V
REF
≤
V
OUT
≤
(V
IN
– 1V), 2.3V
≤
V
IN
≤
30V, 100 µA < I
L
≤
250 mA, T
J
≤
T
J(max)
.
14. Comparator thresholds are expressed in terms of a voltage differential at the FB pin below the nominal reference voltage measured at 6Vinput. To
express these thresholds in terms of output voltage change, multiply by the error amplifier gain = V
OUT
/V
REF
= (R1 + R2)/R2. For example, at a
programmed output voltage of 5V, the error output is guaranteed to go low when the output drops by 95mV × 5V/1.235V = 384mV. Thresholds
remain constant as a percent of V
OUT
as V
OUT
is varied, with the dropout warning occurring at typically 5% below nominal, 7.5% guaranteed.
15. V
SHDN
≥
2V, V
IN
≤
30 V,V
OUT
= 0, with the FB pin connected to TAP.
16. When used in dual supply systems where the regulator load is returned to a negative supply, the output voltage must be diode clamped to ground.
17. Maximum positive supply voltage of 60V must be of limited duration (<10ms) and duty cycle (<1%). The maximum continuous supply voltage is 30V.
September 2007
6
M9999-090607
MICREL [ MICREL SEMICONDUCTOR ]
