MIC5249-3.3BMM-TR [MICROCHIP]
FIXED POSITIVE LDO REGULATOR;
| 型号： | MIC5249-3.3BMM-TR |
| 厂家： | 
MICROCHIP |
| 描述： | FIXED POSITIVE LDO REGULATOR 输出元件 调节器 |
| 文件： | 总7页 (文件大小：167K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
MIC5249
300mA µCap LDO with Programmable Power-On
Reset Delay
General Description
Features
The MIC5249 is an efficient, precise 300mA CMOS
voltage regulator with power-on reset delay which can be
implemented via an external capacitor. It offers 1% initial
accuracy, extremely-low-dropout voltage (typically 400mV
@ 300mA), and low ground current (typically 85mA) over
load.
• 300mA output current
• High PSRR: 65dB@120Hz
• Stable with ceramic output capacitor
• Power-on RESET output with adjustable delay time
• High output accuracy:
–
–
±1.0% initial accuracy
±3.0% over temperature
Designed specifically for noise-critical applications in hand-
held or battery-powered devices, the MIC5249 comes
equipped with a noise reduction feature to filter the output
noise via an external capacitor. Other features of the
MIC5249 include a logic compatible enable pin, current
limit, thermal shutdown, ultra-fast transient response, and
an active clamp to speed up device turnoff.
• Low dropout voltage of 400mV @ 300mA
• Low quiescent current: 85µA
• Zero current shutdown mode
• Thermal shutdown protection
• Current-limit protection
The MIC5249 also works with low-ESR ceramic
capacitors, reducing the amount of board space necessary
for power applications, critical in hand-held wireless
devices.
• Tiny MSOP-8 package
Applications
The MIC5249 is available in the MSOP-8 package.
• Cellular phones
• PDAs
• Fiber optic modules
Data sheets and support documentation can be found on
Micrel’s web site at www.micrel.com.
Typical Application
Ultra-Low Noise Application
Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
M9999-090806
September 2006
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Micrel, Inc.
MIC5249
Ordering Information
Part Number
Standard
Junction
Temperature Range
Voltage*
Package
Pb-Free
MIC5249-1.8BMM
MIC5249-2.5BMM
MIC5249-2.6BMM
MIC5249-2.8BMM
MIC5249-1.8YMM
MIC5249-2.5YMM
MIC5249-2.6YMM
MIC5249-2.8YMM
1.8V
2.5V
2.8V
2.8V
2.85V
3.0V
3.3V
–40°C to +125°C
–40°C to +125°C
–40°C to +125°C
–40°C to +125°C
–40°C to +125°C
–40°C to +125°C
–40°C to +125°C
8-Pin MSOP
8-Pin MSOP
8-Pin MSOP
8-Pin MSOP
8-Pin MSOP
8-Pin MSOP
8-Pin MSOP
MIC5249-2.85BMM MIC5249-2.85YMM
MIC5249-3.0BMM
MIC5249-3.3BMM
MIC5249-3.0YMM
MIC5249-3.3YMM
Note: Other Voltage available. Contact Micrel Marketing for details.
Pin Configuration
8-pin MSOP (MM)
Pin Description
Pin Number
Pin Name
Pin Function
1
CBYP
Reference Bypass: Connect external 0.01F capacitor to GND to reduce output noise.
May be left open.
2
DELAY
Delay Set Input: Connect external capacitor to GND to set the delay of the Error
Flag.
3
4
5
6
7
GND
VIN
Ground.
Supply Input.
Regulator Output.
No Connect.
VOUT
NC
RESET
RESET Output: Open-drain output. Active low indicates an output undervoltage
condition.
8
ENABLE
Enable Input: CMOS compatible input. Logic high = enable; Logic low = shutdown.
Do not leave open.
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Micrel, Inc.
MIC5249
Absolute Maximum Ratings(1)
Operating Ratings(2)
Supply Voltage (VIN)............................................. 0V to +7V
Power Dissipation (PD)...........................Internally Limited(3)
Junction Temperature (TJ) ........................–40°C to +125°C
Lead Temperature (soldering, 5sec.)......................... 260°C
Storage Temperature (Ts) .........................–65°C to +150°C
EDS Rating(4)
Supply voltage (VIN) ........................................ +2.7V to +6V
Enable Voltage (VEN).............................................. 0V to VIN
Junction Temperature (TJ) ........................–40°C to +125°C
Package Thermal Resistance
MSOP (θJA)......................................................200°C/W
Electrical Characteristics
VIN = VOUT + 1V; COUT =1µF, IOUT = 100µA; TJ = 25°C, bold values indicate –40°C to +125°C, unless noted.
Parameter
Condition
Min
Typ
Max
Units
Output Voltage Accuracy
Variation from nominal VOUT
–1.0
–3.0
+1.0
+3.0
%
%
Line Regulation
Load Regulation
Dropout Voltage
VIN = VOUT +1V to 6V
IOUT = 0.1mA to 300mA
IOUT = 100µA
–0.3
0.02
1.5
1
+0.3
3.0
%/V
%
mV
IOUT = 150mA
160
225
275
mV
mV
IOUT = 300mA
IOUT = 0mA
340
500
600
mV
mV
Ground Pin Current
85
100
0.35
65
150
200
1
µA
µA
µA
dB
mA
I
OUT = 300mA
Ground Pin Current in Shutdown
Ripple Rejection
VEN < 0.4V (Regulator OFF)
f = 120Hz, COUT = 2.2µF
VOUT = 0V
Current Limit
300
1.6
440
Enable Input
Enable Input Voltage
Logic low (regulator shutdown)
Logic high (regulator enabled)
VIL < 0.4V (regulator shutdown)
0.4
V
V
Enable Input Current
0.01
0.01
µA
µA
V
IH > 1.6V (regulator enabled)
Delay Input
Delay Pin Current Source
Delay Pin Threshold Voltage
RESET Output
VTH
0.55
1.40
1
µA
V
Threshold for RESET = Logic high
Low threshold, % of VOUT (Flag ON)
High threshold, % of VOUT (Flag OFF)
89
91
93
%
%
V
96
VOL
RESET output logic – low voltage; IRESET = 100µA output in
fault condition
0.020
0.1
IRESET
Flag leakage current, Flag OFF
0.01
µA
Notes:
1. Exceeding the absolute maximum rating may damage the device.
2. The device is not guaranteed to function outside its operating rating.
3. The maximum allowable power dissipation of any TA (ambient temperature) is PD(max) = TJ(max) – TA) ÷ θJA. Exceeding the maximum allowable power
dissipation will result in excessive die temperature, and the regulator will go into thermal shutdown.
4. Devices are ESD sensitive. Handling precautions recommended. Human body model, 1.5k in series with 100pF.
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Micrel, Inc.
MIC5249
Functional Diagram
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Micrel, Inc.
MIC5249
⎛
⎞
Application Information
TDELAY ×IDELAY
⎜
⎜
⎟
⎟
CDELAY
=
VDELAY
⎝
⎠
Enable/Shutdown
where IDELAY is 0.55µA and the VDELAY is 1.4V.
When no capacitor is used, there will be no delay and
the POR output acts like a standard error FLAG output.
The MIC5249 comes with an active-high enable pin that
allows the regulator to be disabled. Forcing the enable
pin low disables the regulator and sends it into a “zero”
off-mode-current state. In this state, current consumed
by the regulator goes nearly to zero. Forcing the enable
pin high enables the output voltage. This part is CMOS
and the enable pin cannot be left floating; a floating
enable pin may cause an indeterminate state on the
output.
Reset Output
The RESET output of the MIC5249 provides the power-
on reset signal based on the capacitor from the DELAY
pin to ground when input power is applied to the
regulator. The reset signal stays low for a preset time
period after power is applied to the regulator, and then
goes high (see “Timing Diagram”).
Input Capacitor
The reset output is an active-low, open-drain output that
drives low when a fault condition AND an undervoltage
detection occurs. Internal circuitry intelligently monitors
overcurrent, overtemperature and dropout conditions
and ORs these outputs together to indicate some fault
condition. The output of that OR gate is ANDed with an
output voltage monitor that detects an undervoltage
condition. The output drives an open-drain transistor to
indicate a fault. This prevents chattering or inadvertent
triggering of the reset. There set must be pulled up using
a resistor form the RESET pin to either the input or the
output.
The MIC5249 is a high performance, high bandwidth
device. Therefore, it requires a well-bypassed input
supply for optimal performance. A 1.0µF capacitor is
required from the input to ground to provide stability.
Low-ESR ceramic capacitors provide optimal perform-
ance at a minimum of space. Additional high-frequency
capacitors such as small valued NPO dielectric type
capacitors help to filter out high frequency noise and are
good practice in any RF-based circuit.
Output Capacitor
The MIC5249 requires an output capacitor for stability.
The design requires 2.2µF or greater on the output to
maintain stability. The design is optimized for use with
low-ESR ceramic chip capacitors. High-ESR capacitors
may cause high frequency oscillation. The maximum
recommended ESR is 300mΩ. The output capacitor can
be increased, but performance has been optimized for a
2.2µF ceramic output capacitor and does not improve
significantly with larger capacitance.
Bypass Pin Input
A bypass capacitor is required from the noise bypass pin
to ground to reduce output voltage noise. The capacitor
bypasses the internal reference. A 0.01µF capacitor is
recommended for applications that require low-noise
outputs. The bypass capacitor can be increased, further
reducing noise and improving PSRR. Turn-on time
increases slightly with respect to bypass capacitance. A
unique quick-start circuit allows the MIC5249 to drive a
large capacitor on the bypass pin without significantly
slowing the turn-on time.
X7R/X5R dielectric-type ceramic capacitors are recom-
mended because of their temperature performance.
X7R-type capacitors change capacitance by 15% over
their operating temperature range and are the most
stable type of ceramic capacitors. Z5U and Y5V
dielectric capacitors change value by as much as 50%
and 60%, respectively, over their operating temperature
ranges. To use a ceramic chip capacitor with Y5V
dielectric, the value must be much higher than anX7R
ceramic capacitor to ensure the same minimum
capacitance over the equivalent operating temperature
range.
Active Shutdown
The MIC5249 also features an active shutdown clamp,
which is a N-Channel MOSFET that turns on when the
device is disabled. This allows the output capacitor and
load to discharge, de-energizing the load.
No-Load Stability
The MIC5249 will remain stable and in regulation with no
load unlike many other voltage regulators. This is
especially important in CMOS RAM keep-alive
application.
Delay Pin Input
The power-on reset function can be implemented on the
MIC5249 by adding an external capacitor from the delay
pinto ground. This external capacitor sets the delay time
(TDELAY) of the RESET output. The capacitor value
required can be easily calculated using the formula:
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Micrel, Inc.
MIC5249
Thermal Consideration
50°C with a minimum footprint layout, the maximum
input voltage for a set output current can be determined
as follows:
The MIC5249 is designed to provide 300mA of
continuous current in a very small package. Maximum
power dissipation can be calculated based on the output
current and the voltage drop across the device. To
determine the maximum power dissipation of the
package, use the junction-to-ambient thermal resistance
of the device and the following basic equation:
125°C − 50°C
200°C/W
⎛
⎜
⎞
⎟
PD(max)
=
⎝
⎠
The junction-to-ambient thermal resistance for the
minimum footprint is 200°C/W, from Table 1. The
maximum power dissipation must not be exceeded for
proper operation. Using the output voltage of 3.0V, and
an output current of 300mA, the maximum input voltage
can be determined. Because this device is CMOS and
the ground current is typically 90µA over the load range,
the power dissipation contributed by the ground current
is < 1.0% and can be ignored for this calculation.
T
− TA
⎛
⎜
⎜
⎝
⎞
⎟
⎟
⎠
J(max)
PD(max)
=
θJA
TJ(max) is the maximum junction temperature of the die,
125°C and TA is the ambient operating temperature. θJA
is layout dependent; Table 1 shows examples of the
junction-to-ambient thermal resistance for the MIC5249.
375mW = (VIN – 3.0V) 300mA
375mW = VIN × 300mA – 900mW
1275mW = VIN × 300mA
Package
θJA Recommended
Minimum Footprint
MSOP-8
200°C/W
V
IN(max) = 4.25V
Table 1. MSOP-8 Thermal Resistance
Therefore, a 3.0V application at 300mA of output current
can accept a maximum input voltage of 4.25V in the
MSOP-8 package. For a full discussion of heat sinking
and thermal effects on the voltage regulators, refer to the
“Regulator Thermals” section of Micrel’s Designing with
The actual power dissipation of the regulator circuit can
be determined using the equation:
PD = (VIN – VOUT ) IOUT + VIN IGND
Low-Dropout Voltage Regulators Handbook
.
Substituting PD(max) for PD and solving for the operating
conditions that are critical to the application will give the
maximum operating conditions for the regulator circuit.
For example, when operating the MIC5249-3.0BMM at
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Micrel, Inc.
MIC5249
Package Information
8-Pin MSOP (MM)
MICREL, INC. 2180 FORTUNE DRIVE SAN JOSE, CA 95131 USA
TEL +1 (408) 944-0800 FAX +1 (408) 474-1000 WEB http:/www.micrel.com
The information furnished by Micrel in this data sheet is believed to be accurate and reliable. However, no responsibility is assumed by Micrel for its
use. Micrel reserves the right to change circuitry and specifications at any time without notification to the customer.
Micrel Products are not designed or authorized for use as components in life support appliances, devices or systems where malfunction of a product
can reasonably be expected to result in personal injury. Life support devices or systems are devices or systems that (a) are intended for surgical implant
into the body or (b) support or sustain life, and whose failure to perform can be reasonably expected to result in a significant injury to the user. A
Purchaser’s use or sale of Micrel Products for use in life support appliances, devices or systems is a Purchaser’s own risk and Purchaser agrees to fully
indemnify Micrel for any damages resulting from such use or sale.
© 2002 Micrel, Incorporated.
M9999-090806
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