MIC2937A/29371/29372
Micrel, Inc.
Note 1:
Absolute maximum ratings indicate limits beyond which damage to the component may occur. Electrical specifications do not
apply when operating the device outside of its rated operating conditions. The maximum allowable power dissipation is a function of the
maximum junction temperature, T
J (MAX)
, the junction-to-ambient thermal resistance,
θ
JA
, and the ambient temperature, T
A
. The maximum
allowable power dissipation at any ambient temperature is calculated using: P
(MAX)
= (T
J(MAX)
– T
A
) /
θ
JA.
Exceeding the maximum allowable
power dissipation will result in excessive die temperature, and the regulator will go into thermal shutdown.
Note 2:
Output voltage temperature coefficient is defined as the worst case voltage change divided by the total temperature range.
Note 3:
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.
Note 4:
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 low values of programmed output voltage, the minimum input supply voltage of 4.3V over temperature must
be taken into account. The MIC2937A operates down to 2V of input at reduced output current at 25°C.
Note 5:
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.
Note 6:
The MIC2937A family features fold-back current limiting. The short circuit (V
OUT
= 0V) current limit is less than the maximum
current with normal output voltage.
Note 7:
Thermal regulation is defined as the change in output voltage at a time T after a change in power dissipation is applied, exclud-
ing load or line regulation effects. Specifications are for a 200mA load pulse at V
IN
= 20V (a 4W pulse) for T = 10ms.
Note 8:
V
REF
≤ V
OUT
≤ (V
IN
– 1 V), 4.3V ≤ V
IN
≤ 26V, 5mA < I
L
≤ 750 mA, T
J
≤ T
J MAX.
Note 9:
Comparator thresholds are expressed in terms of a voltage differential at the Adjust terminal below the nominal reference voltage
measured at 6V input (for a 5V regulator). 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 95 mV x 5V/1.235 V = 384 mV. Thresholds remain constant as a percent of V
OUT
as V
OUT
is varied, with the dropout
warning occurring at typically 5% below nominal, 7.7% guaranteed.
Note 10:
Circuit of Figure 3 with R1 ≥ 150kΩ. V
SHUTDOWN
≥ 2V and V
IN
≤ 26V,V
OUT
= 0.
Note 11:
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.
Note 12:
Maximum positive supply voltage of 60V must be of limited duration (< 100ms) and duty cycle ( ≤ 1%). The maximum continu-
ous supply voltage is 26V.
Schematic Diagram
IN
FEEDBACK
R18
20 kΩ
Q15A
Q15B
Q24
Q25
Q26
OUT
Q9
Q3
R11
18
kΩ
C1
20
pF
Q4
Q5
Q7
SENSE
Q8
Q16
Q6
Q1
10
R11
20.6
kΩ
Q17
Q14
R17
12 kΩ
R27
V TAP
R28
Q2
Q20
Q42
R1
20 kΩ
R8
31.4 k Ω
R10
150
kΩ
Q22
R2
50 kΩ
R5
180
kΩ
Q13
R6
140
kΩ
C2
40 pF
Q21
R15
100 k Ω
R16
30 kΩ
Q23
R9
27.8 k Ω
Q40
Q41
R30
30
kΩ
Q12
Q11
R12
110
kΩ
R13
100
kΩ
R14
350
kΩ
Q18
R3
50 kΩ
Q19
Q29
R17
10Ω
R4
13 kΩ
Q28
R21 8 Ω
50 kΩ
Q37
Q30
Q31
R24
50 kΩ
Q36
10 kΩ
R22
150 k Ω
R23 60 k Ω
SHDN
ERROR
Q38
R26
60 kΩ
Q34
R25
2.8 kΩ
DENOTES CONNECTION ON
MIC2937A-xx AND MIC29371-xx
VERSIONS ONLY
Q39
GND
May 2006
5
MIC2937A/29371/29372
MICREL [ MICREL SEMICONDUCTOR ]
