MIC2937A/29371/29372
Micrel
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, excluding
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 continuous
supply voltage is 26V.
Schematic Diagram
IN
FEEDBACK
R18
20kΩ
Q15A
Q15B
Q24
Q26
Q25
Q9
Q3
OUT
R11
18
kΩ
Q4
Q7
Q5
Q8
SENSE
Q14
Q6
Q1
10
R1
20 kΩ
C1
20
pF
R11
20.6
kΩ
Q2
Q20
Q16
Q17
R17
12 kΩ
R27
V TAP
R28
Q42
R8
31.4 kΩ
R10
150
kΩ
Q22
Q21
C2
40 pF
Q23
R2
50 kΩ
R5
180
kΩ
Q13
R6
140
kΩ
Q12
R9
27.8 kΩ
R15
100 kΩ
Q40
Q41
R12
110
kΩ
Q11
R13
100
kΩ
R14
350
kΩ
Q29
R16
30 kΩ
R17
10
Ω
R30
30
kΩ
Q18
Q19
Q28
R3
50 kΩ
R4
13 kΩ
R21 8
Ω
50 kΩ
Q37
Q36
Q30 Q31
SHDN
R22
150 kΩ
R24
50 kΩ
R23 60 kΩ
10 kΩ
ERROR
Q38
R26
60 kΩ
Q34
R25
2.8 kΩ
DENOTES CONNECTION ON
MIC2937A-xx AND MIC29371-xx
VERSIONS ONLY
Q39
GND
MIC2937A/29371/29372
22
October 1999
MICREL [ MICREL SEMICONDUCTOR ]
