Page 1
MIC5270 Micrel
MIC5270
IttyBitty™ Negative Low-Dropout Regulator
Preliminary Information
General Description
The MIC5270 is a µCap 100mA negative regulator in a SOT23-5 package. With better than 2% initial accuracy, this
regulator provides a very accurate supply voltage for applications that require a negative rail. The MIC5270 sinks 100mA
of output current at very low dropout voltage (600mV maximum at 100mA of output current).
The µCap regulator design is optimized to work with lowvalue, low-cost ceramic capacitors. The output typically requires only a 1µF capacitance for stability.
Designed for applications where small packaging and efficiency are critical, the MIC5270 combines LDO design expertise with IttyBitty™ packaging to improve performance and
reduce power dissipation. Ground current is optimized to help
improve battery life in portable applications.
The MIC5270 is available in the SOT-23-5 package for space
saving applications and it is available with fixed –3.0V, –4.1V,
and –5.0V outputs.
Ordering Information
Part Number Voltage Temperature Range Package
MIC5270-3.0BM5 –3.0V –40°C to +85°C SOT-23-5
MIC5270-4.1BM5 –4.1V –40°C to +85°C SOT-23-5
MIC5270-5.0BM5 –5.0V –40°C to +85°C SOT-23-5
Features
• IttyBitty™ SOT-23-5 packaging
• Low dropout voltage
• Low ground current
• Tight initial accuracy
• Tight load and line regulation
• Thermal shutdown
• Current limiting
• Stable with low-ESR ceramic capacitors
Applications
• GaAsFET bias
• Portable cameras and video recorders
• PDAs
• Battery-powered equipment
Typical Application
MIC5270-5.0
2
V
IN
GND
54
–OUT–IN
1µF 10µF
V
OUT
–5.0V–6.0V
Pin Description
Pin Number Pin Name Pin Function
1 NC Not internally connected.
2 GND Ground
3 NC Not internally connected.
4 –OUT Negative Regulator Output
5 –IN Negative Supply Input
IttyBitty is a trademark of Micrel, Inc.
Pin Configuration
NC
MIC5270-x.xBM5
NC
GND
13
2
LLxx
45
–IN–OUT
March 1999 283 MIC5270
Page 2
MIC5270 Micrel
Absolute Maximum Ratings (Note 1)
Input Voltage (V
Power Dissipation (PD) ............................ Internally Limited
Junction Temperature (TJ) ....................... –40°C to +125°C
)....................................... –20V to +20V
–IN
Operating Ratings (Note 2)
Input Voltage (VIN) .......................................... –16V to –2V
Junction Temperature (TJ) ....................... –40°C to +125°C
Thermal Resistance (θJA)......................................... Note 4
Lead Temperature (soldering, 5 sec.) ....................... 260°C
Storage Temperature (TS) ....................... –65°C to +150°C
ESD Rating, Note 3
Electrical Characteristics
VIN = V
Symbol Parameter Condition Min Typ Max Units
V
OUT
∆V
OUT
∆V
OUT/VOUT
∆V
OUT/VOUT
VIN – V
I
GND
PSRR Ripple Rejection f = 120Hz 50 dB
I
LIMIT
∆V
OUT
Note 1. Exceeding the absolute maximum rating may damage the device.
Note 2. The device is not guaranteed to function outside its operating rating.
Note 3. Devices are ESD sensitive. Handling precautions recommended.
Note 4. The maximum allowable power dissipation is a function of the maximum junction temperature, T
Note 5. Output voltage temperature coefficient is defined as the worst case voltage change divided by the total temperature range.
Note 6. Regulation is measured at constant junction temperature using low duty cycle pulse testing. Parts are tested for load regulation in the load
Note 7. Dropout voltage is defined as the input to output differential at which the output voltage drops 2% below its nominal value measured at 1V
Note 8. Ground pin current is the regulator quiescent current plus pass transistor base current. The total current drawn from the supply is the sum of
Note 9. 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
– 1.0V; C
OUT
Output Voltage Accuracy Variation from nominal V
= 4.7µF, I
OUT
= 100µA; TJ = 25°C, bold values indicate –40°C ≤ TJ ≤ +125°C; unless noted.
OUT
OUT
–2 2 %
–3 3 %
/∆T Output Voltage Temperature Note 5 100 ppm/°C
Coefficient
Line Regulation VIN = V
Load Regulation I
OUT
Dropout Voltage, Note 7 I
Ground Current, Note 8 I
Current Limit V
/∆P
Thermal Regulation Note 9 0.05 %/W
D
resistance, θJA, and the ambient temperature, TA. The maximum allowable power dissipation at any ambient temperature is calculated using:
P
= (T
D(max)
temperature, and the regulator will go into thermal shutdown. See the “Thermal Considerations” section for details.
range from 100µA to 100mA. Changes in output voltage due to heating effects are covered by the thermal regulation specification.
differential.
the load current plus the ground pin current.
regulation effects. Specifications are for a 100mA load pulse at VIN = –16V for t = 10ms.
J(max)–TA
) ÷ θJA, where θJA is 235°C/W. Exceeding the maximum allowable power dissipation will result in excessive die
OUT
OUT
I
OUT
I
OUT
I
OUT
OUT
I
OUT
I
OUT
I
OUT
OUT
– 1V to –16V 0.055 0.15 %/V
OUT
= 100µA to 100mA, Note 6 2.0 %
= 100µA35mV
= 10mA 250 mV
= 50mA 360 450 mV
= 100mA 480 600 mV
= 100µA70µA
= 10mA 250 µA
= 50mA 0.7 mA
= 100mA 2.1 3.0 mA
= 0V 160 300 mA
, the junction-to-ambient thermal
J(max)
MIC5270 284 March 1999
Page 3
MIC5270 Micrel
Functional Diagram
GND
V
IN
MIC5270-x.x
V
OUT
March 1999 285 MIC5270
Page 4
MIC5270 Micrel
P
125 C 25 C
235 C/W
D(max)
=
°− °
°
Applications Information
The MIC5270 is a general-purpose negative regulator that
can be used in any system that requires a clean negative
voltage from a negative output. This includes post regulating
of dc-dc converters (transformer based or charge pump
based voltage converters). These negative voltages typically
require a negative low-dropout voltage regulator to provide a
clean output from typically noisy lines.
Input Capacitor
A 1µF input capacitor should be placed from IN to GND if
there is more than 2 inches of wire or trace between the input
and the ac filter capacitor, or if a battery is used as the input.
Output Capacitor
The MIC5270 requires an output capacitor for stable operation. A minimum of 1µF of output capacitance is required. The
output capacitor can be increased without limitation to improve transient response. The output does not require ESR
to maintain stability, therefore a ceramic capacitor can be
used. High-ESR capacitors may cause instability. Capacitors
with an ESR of 3Ω or greater at 100kHz may cause a high
frequency oscillation.
Low-ESR tantalums are recommended due to the tight capacitance tolerance over temperature.
Ceramic chip capacitors have a much greater dependence
on temperature, depending upon the dielectric. The X7R is
recommended for ceramic capacitors because the dielectric
will change capacitance value by approximately 15% over
temperature. The Z5U dielectric can change capacitance
value by as much 50% over temperature, and the Y5V
dielectric can change capacitance value by as much as 60%
over temperature. To use a ceramic chip capacitor with the
Y5V dielectric, the value must be much higher than a tantalum to ensure the same minimum capacitor value over
temperature.
No-Load Stability
The MIC5270 does not require a load for stability.
Thermal Considerations
Absolute values will be used for thermal calculations to clarify
what is meant by power dissipation and voltage drops across
the part.
Proper thermal design for the MIC5270-5.0BM5 can be
accomplished with some basic design criteria and some
simple equations. The following information must be known
to implement your regulator design:
VIN = input voltage
V
= output voltage
OUT
I
= output current
OUT
TA = ambient operating temperature
I
= ground current
GND
Maximum power dissipation can be determined by knowing
the ambient temperature, TA, the maximum junction tem-
perature, 125°C, and the thermal resistance, junction to
ambient. The thermal resistance for this part, assuming a
minimum footprint board layout, is 235°C/W. The maximum
power dissipation at an ambient temperature of 25°C can be
determined with the following equation:
P
P 425mW
D(max)
D(max)
=
=
TT
−
J(max) A
θ
JA
The actual power dissipation of the regulator circuit can be
determined using one simple equation.
PVVI VI
=−
()
DIN
Substituting P
OUT OUT
, determined above, for PD and solving
D(max)
+⋅
IN
GND
for the operating conditions that are critical to the application
will give the maximum operating conditions for the regulator
circuit. The maximum power dissipation number cannot be
exceeded for proper operation of the device. The maximum
input voltage can be determined using the output voltage of
5.0V and an output current of 100mA. Ground current, of 1mA
for 100mA of output current, can be taken from the Electrical
Characteristics section of the data sheet.
425mW V 5.0V 100mA V 1mA
425mW 100mA V 1mA V 500mW
925mW 101mA V
V 9.16Vmax
IN
=−
()
IN IN
=⋅+⋅
()
=⋅
IN IN
IN
+⋅
−
=
Therefore, a –5.0V application at 100mA of output current
can accept a maximum input voltage of –9.16V in a SOT-23-5
package. For a full discussion of heat sinking and thermal
effects on voltage regulators, refer to Regulator Thermals
section of Micrel’s Designing with Low-Dropout Voltage Regu-
lators handbook.
MIC5270 286 March 1999
Loading...