MIC5249-2.8YMM TR - Micrel

MIC5249

300mA µCap LDO with

Programmable Power-On Reset Delay

Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com

General Description

The MIC5249 is an efficient, precise 300mA CMOS

voltage regulator with power on reset (POR) 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.

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.

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.

The MIC5249 is available in the MSOP-8 package.

Data sheets and support documentation can be found on

Micrel’s web site at: www.micrel.com.

Features

• 300mA output current

• High PSRR: 65dB@120Hz

• Stable with ceramic output capacitor

• Power-on-Reset (POR) output with adjustable delay

time

• High output accuracy:

− ±1.0% initial accuracy

− ±3.0% over temperature

• Low dropout voltage of 340mV @ 300mA

• Low quiescent current: 85µA

• Zero current shutdown mode

• Thermal-shutdown and current-limit protection

• Tiny MSOP-8 package

Applications

• Cellular phones

• PDAs

• Fiber optic modules

Typical Application

Ultra-Low Noise Application

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Ordering Information

Part Number Voltage(1) Junction Temperature Range Package

MIC5249-1.5YMM 1.5V –40°C to +125°C 8-Pin MSOP

MIC5249-1.8YMM 1.8V –40°C to +125°C 8-Pin MSOP

MIC5249-2.5YMM 2.5V –40°C to +125°C 8-Pin MSOP

MIC5249-2.6YMM 2.6V –40°C to +125°C 8-Pin MSOP

MIC5249-2.8YMM 2.8V –40°C to +125°C 8-Pin MSOP

MIC5249-2.85YMM 2.85V –40°C to +125°C 8-Pin MSOP

MIC5249-3.0YMM 3.0V –40°C to +125°C 8-Pin MSOP

MIC5249-3.3YMM 3.3V –40°C to +125°C 8-Pin MSOP

Note:

1. Other voltages available. Contact Micrel Marketing for details.

Pin Configur ation

1CBYP

DELAY

GND

VIN

8 ENABLE

RESET

VOUT

8-pin MSOP (MM)

Pin Description

Pin Number Pin Name Pin Function

1 CBYP

Reference Bypass. Connect external 0.01µF 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 GND Ground.

4 VIN Supply Input.

5 VOUT Regulator Output.

6 NC No Connect.

7 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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Absolute Maximum Ratings(1)

Supply Voltage (VIN)............................................. 0V to +7V

Enable Voltage (VEN)............................................ 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

ESD Rating(4)................................................. ESD Sensitive

Operating Ratings(2)

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)......................................................160°C/W

Electrical Characteristics

VIN = VOUT + 1V; COUT = 2.2µF, 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 VIN = VOUT +1V to 6V –0.3 0.02 +0.3 %/V

Load Regulation IOUT = 0.1mA to 300mA 1.5 3.0 %

IOUT = 100µA 1

IOUT = 150mA 160 225

275

Dropout Voltage

IOUT = 300mA 340 500

600

IOUT = 0mA 85 150

Ground Pin Current IOUT = 300mA 100 200 µA

Ground Pin Current in Shutdown VEN < 0.4V (Regulator OFF) 0.35 1 µA

Ripple Rejection f = 120Hz, COUT = 2.2µF 65 dB

Current Limit VOUT = 0V 300 440 mA

Enable Input

Logic low (regulator shutdown) 0.4

Enable Input Voltage Logic high (regulator enabled) 1.6 V

VIL < 0.4V (regulator shutdown) 0.01

Enable Input Current VIH > 1.6V (regulator enabled) 0.01 µA

Delay Input

Delay Pin Current Source 0.55 1 µA

Delay Pin Threshold Voltage Threshold for RESET = Logic high 1.40 V

RESET Output

Low threshold, % of VOUT (Flag ON) 89 91

VTH High threshold, % of VOUT (Flag OFF) 93 96 %

VOL RESET output logic – low voltage; IRESET = 100µA output

in fault condition 0.020

0.1 V

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, 1.5kΩ in series with 100pF.

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Functional Diagram

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Application Information

Enable/Shutdown

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.

Input Capacitor

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

performance 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 of 2.2µF or

greater 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.

X7R/X5R dielectric-type ceramic capacitors are

recommended 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.

DELAY Pin Input

The power-on-reset (POR) function can be implemented

on the MIC5249 by adding an external capacitor from

the DELAY pin to ground. This external capacitor sets

the delay time (TDELAY) of the RESET output.

The capacitor value required can be easily calculated

using the formula:

⎟

⎠

⎞

⎜

⎝

⎛×

DELAY

DELAYDELAY

DELAY V

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.

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.

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.

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.

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.

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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 MIC5249-3.0YMM at

50°C with a minimum footprint layout, the maximum

input voltage for a set output current can be determined

as follows:

Thermal Considerations

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:

⎟

⎠

⎞

⎜

⎝

⎛

°−°

=C/W160 C50C125

PD(max)

⎟

⎠

⎞

⎜

⎝

⎛−

AJ(max)

D(max) θ

The junction-to-ambient thermal resistance for the

minimum footprint is 160°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:

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.

Package θJA Recommended Minimum Footprint

MSOP-8 160°C/W

468mW = (VIN – 3.0V) 300mA

Table 1. MSOP-8 Thermal Resistance

468mW = VIN × 300mA – 900mW

1368mW = VIN × 300mA

VIN(max) = 4.56V

The actual power dissipation of the regulator circuit can

be determined using the equation:

Therefore, a 3.0V application at 300mA of output current

can accept a maximum input voltage of 4.56V 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

Low-Dropout Voltage Regulators Handbook.

D = (VIN – VOUT ) IOUT + VIN IGND

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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

Micrel makes no representations or warranties with respect to the accuracy or completeness of the information furnished in this data sheet. This

information is not intended as a warranty and Micrel does not assume responsibility for its use. Micrel reserves the right to change circuitry,

specifications and descriptions at any time without notice. No license, whether express, implied, arising by estoppel or otherwise, to any intellectual

property rights is granted by this document. Except as provided in Micrel’s terms and conditions of sale for such products, Micrel assumes no liability

whatsoever, and Micrel disclaims any express or implied warranty relating to the sale and/or use of Micrel products including liability or warranties

relating to fitness for a particular purpose, merchantability, or infringement of any patent, copyright or other intellectual property right.

Micrel Products are not designed or authorized for use as components in life support appliances, devices or systems where malfunction of a product

reasonably be expected to result in personal injury. Life support devices or systems are devices or systems that (a) are intended for surgical impla

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.

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