MIC29302HWU Datasheet, PDF (9/10 Pages) Micrel Semiconductor – High-Current Low-Dropout Regulators

Micrel, Inc.
Then determine the maximum power dissipation allowed
that would not exceed the IC’s maximum junction
temperature (125C) without the useof a heat sink by:
P_D(MAX) = (T_J(MAX)–T_A)/θ_JA
= (125C–75C)/(56C/W) = 0.893W
Eq. 5
Capacitor Requirements
For stability and to minimize output noise, a capacitor on
the regulator output is necessary. The value of this
capacitor is dependent upon the output current; lower
currents allow smaller capacitors. The MIC29302HWU is
stable with minimum of 100µF. This capacitor need not
be an expensive low ESR type: aluminum electrolytics
are adequate. In fact, extremely low ESR capacitors may
contribute to instability. Tantalum capacitors are
recommended for systems where fast load transient
response is important.
Where the regulator is powered from a source with high
AC impedance, a 0.1µF capacitor connected between
Input and GND is recommended. This capacitor should
have good characteristics to above 250kHz.
MIC29302HWU
Minimum Load Current
The MIC29300HWU is specified between finite loads. If
the output current below 7mA, leakage currents
dominate and the output voltage rises.
Adjustable Regulator Design
The MIC20302HWU allows programming the output
voltage anywhere between 1.25V and the 25V. Two
resistors are used. The resistor values are calculated by
R₁

R₂


V_OUT
1.240
 1_{}
Eq 6:
R₁

R₂


V_OUT
1.240
 1_{}
Eq 6.
where V_OUT is the desired output voltage. Figure 3 shows
component definition. Applications with widely varying
load currents may scale the resistors to draw the
minimum load current required for proper operation (see
“Minimum Load Current” sub-section).
Enable Input
MIC29302HWU features an enable (EN) input that
allows ON/OFF control of the device. Special design
allows “zero” current drain when the device is disabled—
only microamperes of leakage current flows. The EN
input has TTL/CMOS compatible thresholds for simple
interfacing with logic, or may be directly tied to ≤30V.
Enabling the regulator requires approximately 20µA of
current.
November 11, 2013
9
Revision 1.0