MIC3975YMM TR - MICROCHIP TECHNOLOGY

February 2005 1 MIC3975

MIC3975 Micrel

Ordering Information

Part Number

Standard Pb-Free Voltage Junction Temp. Range Package

MIC3975-1.65BMM MIC3975-1.65YMM 1.65V –40°C to +125°C MSOP-8

MIC3975-1.8BMM MIC3975-1.8YMM 1.8V –40°C to +125°C MSOP-8

MIC3975-2.5BMM MIC3975-2.5YMM 2.5V –40°C to +125°C MSOP-8

MIC3975-3.0BMM MIC3975-3.0YMM 3.0V –40°C to +125°C MSOP-8

MIC3975-3.3BMM MIC3975-3.3YMM 3.3V –40°C to +125°C MSOP-8

MIC3975-5.0BMM MIC3975-5.0YMM 5.0V –40°C to +125°C MSOP-8

MIC3975BMM MIC3975YMM Adj. –40°C to +125°C MSOP-8

MIC3975

750mA µCap Low-Voltage Low-Dropout Regulator

General Description

The MIC3975 is a 750mA low-dropout linear voltage regula-

tors that provide low-voltage, high-current output from an

extremely small package. Utilizing Micrel’s proprietary Super

βeta PNP™ pass element, the MIC3975 offers extremely low

dropout (typically 300mV at 750mA) and low ground current

(typically 6.5mA at 750mA).

The MIC3975 is ideal for PC add-in cards that need to con-

vert from standard 5V to 3.3V or 3.0V, 3.3V to 2.5V or 2.5V

to 1.8V or 1.65V. A guaranteed maximum dropout voltage

of 500mV over all operating conditions allows the MIC3975

to provide 2.5V from a supply as low as 3.0V and 1.8V or

1.65V from a supply as low as 2.25V.

The MIC3975 is fully protected with overcurrent limiting,

thermal shutdown, and reversed-battery protection. Fixed

voltages of 5.0V, 3.3V, 3.0, 2.5V, 1.8V, and 1.65V are avail-

able. An adjustable output voltage option is available for

voltages down to 1.24V.

For other voltages, contact Micrel.

Typical Applications

Features

• Fixed and adjustable output voltages to 1.24V

• 300mV typical dropout at 750mA

Ideal for 3.0V to 2.5V conversion

Ideal for 2.5V to 1.8V or 1.65V conversion

• Stable with ceramic capacitor

• 750mA minimum guaranteed output current

• 1% initial accuracy

• Low ground current

• Current limiting and thermal shutdown

• Reversed-battery protection

• Reversed-leakage protection

• Fast transient response

• Low-proﬁle MSOP-8

Applications

• Fiber optic modules

• LDO linear regulator for PC add-in cards

• PowerPC™ power supplies

• High-efﬁciency linear power supplies

• SMPS post regulator

• Multimedia and PC processor supplies

• Battery chargers

• Low-voltage microcontrollers and digital logic

Super βeta PNP is a trademark of Micrel, Inc.

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

100k

2.5V

Error

Flag

Output

3.3V

10F

ceramic

OUT

FLG

GND

MIC3975-2.5BMM

ENABLE

SHUTDOWN

2.5V/750mA Regulator with Error Flag

1.5V

2.5V

10F

ceramic

OUT

ADJ

GND

MIC3975BMM

ENABLE

SHUTDOWN

1.5V/750mA Adjustable Regulator

MIC3975 Micrel

MIC3975 2 February 2005

Pin Conﬁguration

1EN

FLG

OUT

8 GND

GND

MIC3975-x.x

Fixed

MSOP-8 (MM)

1EN

ADJ

OUT

8 GND

GND

Adjustable

Pin Description

Pin No. Pin No. Pin Name Pin Function

Fixed Adjustable

1 1 EN Enable (Input): CMOS-compatible control input. Logic high = enable, logic

low or open = shutdown.

2 2 IN Supply (Input)

3 FLG Flag (Output): Open-collector error ﬂag output. Active low = output under-

voltage.

3 ADJ Adjustment Input: Feedback input. Connect to resistive voltage-divider net-

work.

4 4 OUT Regulator Output

5–8 5–8 GND Ground

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MIC3975 Micrel

Electrical Characteristics(Note 12)

VIN = VOUT + 1V; VEN = 2.25V; TJ = 25°C, bold values indicate –40°C ≤ TJ ≤ +125°C; unless noted

Symbol Parameter Condition Min Typ Max Units

VOUT Output Voltage 10mA –1 1 %

10mA ≤ IOUT ≤ 750mA, VOUT + 1V ≤ VIN ≤ 8V –2 2 %

Line Regulation IOUT = 10mA, VOUT + 1V ≤ VIN ≤ 16V 0.06 0.5 %

Load Regulation VIN = VOUT + 1V, 10mA ≤ IOUT ≤ 750mA, 0.2 1 %

ΔVOUT/ΔT Output Voltage Temp. Coefﬁcient, 40 100

ppm/°C

Note 5

VDO Dropout Voltage, Note 6 IOUT = 100mA, ΔVOUT = –1% 140 200 mV

250 mV

IOUT = 500mA, ΔVOUT = –1% 225 mV

IOUT = 750mA, ΔVOUT = –1% 300 500 mV

IGND Ground Current, Note 7 IOUT = 100mA, VIN = VOUT + 1V 400 µA

IOUT = 500mA, VIN = VOUT + 1V 4 mA

IOUT = 750mA, VIN = VOUT + 1V 7.5 15 mA

IOUT(lim) Current Limit VOUT = 0V, VIN = VOUT + 1V 1.8 2.5 A

Enable Input

VEN Enable Input Voltage logic low (off) 0.8 V

logic high (on) 2.25 V

IEN Enable Input Current VEN = 2.25V 1 15 30 µA

75 µA

VEN = 0.8V 2 µA

4 µA

Flag Output

IFLG(leak) Output Leakage Current VOH = 16V 0.01 1 µA

2 µA

VFLG(do) Output Low Voltage VIN = 2.250V, IOL, = 250µA, Note 9 210 300 mV

400 mV

VFLG Low Threshold % of VOUT 93 %

High Threshold % of VOUT 99.2 %

Hysteresis 1 %

Absolute Maximum Ratings (Note 1)

Supply Voltage (VIN) .......................................–20V to +20V

Enable Voltage (VEN) .................................................. +20V

Storage Temperature (TS) ........................ –65°C to +150°C

Lead Temperature (soldering, 5 sec.) ........................ 260°C

ESD, Note 3

Operating Ratings (Note 2)

Supply Voltage (VIN) ................................... +2.25V to +16V

Enable Voltage (VEN) .................................................. +16V

Maximum Power Dissipation (PD(max)) ..................... Note 4

Junction Temperature (TJ) ........................ –40°C to +125°C

Package Thermal Resistance

MSOP-8 (θJA) ...................................................... 80°C/W

MIC3975 Micrel

MIC3975 4 February 2005

Symbol Parameter Condition Min Typ Max Units

Adjustable Output Only

Reference Voltage 1.228 1.240 1.252 V

1.215 1.265 V

Note 10 1.203 1.277 V

Adjust Pin Bias Current 40 80 nA

120 nA

Reference Voltage Note 11 20

ppm/°C

Temp. Coefﬁcient

Adjust Pin Bias Current 0.1 nA/°C

Temp. Coefﬁcient

Note 1. Exceeding the absolute maximum ratings 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. PD(max) = (TJ(max) – TA) ÷ θJA, where θJA depends upon the printed circuit layout. See “Applications Information.”

Note 5. Output voltage temperature coefﬁcient is ΔVOUT(worst case) ÷ (TJ(max) – TJ(min)) where TJ(max) is +125°C and TJ(min) is –40°C.

Note 6. VDO = VIN – VOUT when VOUT decreases to 98% of its nominal output voltage with VIN = VOUT + 1V. For output voltages below 2.25V, dropout

voltage is the input-to-output voltage differential with the minimum input voltage being 2.25V. Minimum input operating voltage is 2.25V.

Note 7. IGND is the quiescent current. IIN = IGND + IOUT.

Note 8. VEN ≤ 0.8V, VIN ≤ 8V, and VOUT = 0V.

Note 9. For a 2.5V device, VIN = 2.250V (device is in dropout).

Note 10. VREF ≤ VOUT ≤ (VIN – 1V), 2.25V ≤ VIN ≤ 16V, 10mA ≤ IL ≤ 750mA, TJ = TMAX.

Note 11. 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 VIN = 16V for t = 10ms.

Note 12. Speciﬁcation for packaged product only.

February 2005 5 MIC3975

MIC3975 Micrel

Typical Characteristics

MIC3975 Micrel

MIC3975 6 February 2005

February 2005 7 MIC3975

MIC3975 Micrel

Functional Characteristics

Load Transient Response

TIME (200s/div.)

LOAD CURRENT

(500mA/div.)

OUTPUT VOLTAGE

(200mV/div.)

VIN = 3.3V

VOUT = 2.5V

COUT = 10F Ceramic

750mA

100mA

Load Transient Response

TIME (200s/div.)

LOAD CURRENT

(500mA/div.)

OUTPUT VOLTAGE

(200mV/div.)

VIN = 3.3V

VOUT = 2.5V

COUT = 10F Ceramic

750mA

10mA

VOUT = 2.5V

COUT = 10F Ceramic

ILOAD = 10mA

3.3V

5.0V

Line Transient Response

TIME (200s/div.)

INPUT VOLTAGE

(1V/div.)

OUTPUT VOLTAGE

(50mV/div.)

MIC3975 Micrel

MIC3975 8 February 2005

Functional Diagrams

Ref.

18V

O.V.

ILIMIT

Thermal

Shut-

down

1.240V1.180V

FLAG

GND

OUT

MIC3975 Fixed Regulator with Flag and Enable Block Diagram

Ref.

18V

O.V.

ILIMIT

Thermal

Shut-

down

1.240V

GND

OUT

ADJ

MIC3975 Adjustable Regulator Block Diagram

February 2005 9 MIC3975

MIC3975 Micrel

Applications Information

The MIC3975 is a high-performance low-dropout voltage regu-

lator suitable for moderate to high-current voltage regulator

applications. Its 500mV dropout voltage at full load and over-

temperature makes it especially valuable in battery-powered

systems and as high-efﬁciency noise ﬁlters in post-regulator

applications. Unlike older NPN-pass transistor designs, where

the minimum dropout voltage is limited by the base-to-emit-

ter voltage drop and collector-to-emitter saturation voltage,

dropout performance of the PNP output of these devices is

limited only by the low VCE saturation voltage.

A trade-off for the low dropout voltage is a varying base drive

requirement. Micrel’s Super βeta PNP™ process reduces this

drive requirement to only 2% of the load current.

The MIC3975 regulator is fully protected from damage due to

fault conditions. Linear current limiting is provided. Output cur-

rent during overload conditions is constant. Thermal shutdown

disables the device when the die temperature exceeds the

maximum safe operating temperature. Transient protection

allows device (and load) survival even when the input volt-

age spikes above and below nominal. The output structure

of these regulators allows voltages in excess of the desired

output voltage to be applied without reverse current ﬂow.

MIC3975x.x

IN OUT

GND

CIN COUT

VIN VOUT

Figure 1. Capacitor Requirements

Output Capacitor

The MIC3975 requires an output capacitor for stable opera-

tion. As a µCap LDO, the MIC3975 can operate with ceramic

output capacitors as long as the amount of capacitance is

10µF or greater. For values of output capacitance lower than

10µF, the recommended ESR range is 200mΩ to 2Ω. The

minimum value of output capacitance recommended for the

MIC3975 is 4.7µF.

For 10µF or greater the ESR range recommended is less than

1Ω. Ultra-low ESR ceramic capacitors are recommended

for output capacitance of 10µF or greater to help improve

transient response and noise reduction at high frequency.

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 operat-

ing temperature ranges. To use a ceramic chip capacitor with

Y5V dielectric, the value must be much higher than an X7R

ceramic capacitor to ensure the same minimum capacitance

over the equivalent operating temperature range.

Input Capacitor

An input capacitor of 1µF or greater is recommended when

the device is more than 4 inches away from the bulk ac supply

capacitance or when the supply is a battery. Small, surface

mount, ceramic chip capacitors can be used for bypassing.

Larger values will help to improve ripple rejection by bypass-

ing the input to the regulator, further improving the integrity

of the output voltage.

Error Flag

The MIC3975 features an error ﬂag (FLG), which monitors

the output voltage and signals an error condition when this

voltage drops 5% below its expected value. The error ﬂag is

an open-collector output that pulls low under fault conditions

and may sink up to 10mA. Low output voltage signiﬁes a

number of possible problems, including an overcurrent fault

(the device is in current limit) or low input voltage. The ﬂag

output is inoperative during overtemperature conditions. A

pull-up resistor from FLG to either VIN or VOUT is required

for proper operation. For information regarding the minimum

and maximum values of pull-up resistance, refer to the graph

in the typical characteristics section of the data sheet.

Enable Input

The MIC3975 features an active-high enable input (EN) that

allows on-off control of the regulator. Current drain reduces to

“zero” when the device is shutdown, with only microamperes

of leakage current. The EN input has TTL/CMOS compatible

thresholds for simple logic interfacing. EN may be directly tied

to VIN and pulled up to the maximum supply voltage

Transient Response and 3.3V to 2.5V or 2.5V to 1.8V or

1.65V Conversion

The MIC3975 has excellent transient response to variations in

input voltage and load current. The device has been designed

to respond quickly to load current variations and input voltage

variations. Large output capacitors are not required to obtain

this performance. A standard 10µF output capacitor, is all

that is required. Larger values help to improve performance

even further.

By virtue of its low-dropout voltage, this device does not satu-

rate into dropout as readily as similar NPN-based designs.

When converting from 3.3V to 2.5V or 2.5V to 1.8V or 1.65V,

the NPN based regulators are already operating in dropout,

with typical dropout requirements of 1.2V or greater. To convert

down to 2.5V or 1.8V without operating in dropout, NPN-based

regulators require an input voltage of 3.7V at the very least.

The MIC3975 regulator will provide excellent performance

with an input as low as 3.0V or 2.5V respectively. This gives

the PNP based regulators a distinct advantage over older,

NPN based linear regulators.

Minimum Load Current

The MIC3975 regulator is speciﬁed between ﬁnite loads. If

the output current is too small, leakage currents dominate

and the output voltage rises. A 10mA minimum load current

is necessary for proper regulation.

MIC3975 Micrel

MIC3975 10 February 2005

Adjustable Regulator Design

VOUT

VIN

COUT

OUT

ADJ

GND

MIC3975

ENABLE

SHUTDOWN

V 1.240V 1 R1

OUT  











Figure 2. Adjustable Regulator with Resistors

The MIC3975 allows programming the output voltage any-

where between 1.24V and the 16V maximum operating rating

of the family. Two resistors are used. Resistors can be quite

large, up to 1MΩ, because of the very high input impedance

and low bias current of the sense comparator: The resistor

values are calculated by:

R1 R2 V

1.240 1

OUT

 











Where VO is the desired output voltage. Figure 2 shows

component deﬁnition. Applications with widely varying load

currents may scale the resistors to draw the minimum load

current required for proper operation (see above).

Power MSOP-8 Thermal Characteristics

One of the secrets of the MIC3975’s performance is its power

MSO-8 package featuring half the thermal resistance of a

standard MSO-8 package. Lower thermal resistance means

more output current or higher input voltage for a given pack-

age size.

Lower thermal resistance is achieved by joining the four

ground leads with the die attach paddle to create a single-

piece electrical and thermal conductor. This concept has

been used by MOSFET manufacturers for years, proving

very reliable and cost effective for the user.

Thermal resistance consists of two main elements, θJC (junc-

tion-to-case thermal resistance) and θCA (case-to-ambient

thermal resistance). See Figure 3. θJC is the resistance from

the die to the leads of the package. θCA is the resistance

from the leads to the ambient air and it includes θCS (case-

to-sink thermal resistance) and θSA (sink-to-ambient thermal

resistance).

Using the power MSOP-8 reduces the θJC dramatically and

allows the user to reduce θCA. The total thermal resistance,

θJA (junction-to-ambient thermal resistance) is the limiting

factor in calculating the maximum power dissipation capabil-

ity of the device. Typically, the power MSOP-8 has a θJA of

80°C/W, this is signiﬁcantly lower than the standard MSOP-8

which is typically 160°C/W. θCA is reduced because pins 5

through 8 can now be soldered directly to a ground plane

which signiﬁcantly reduces the case-to-sink thermal resistance

and sink to ambient thermal resistance.

Low-dropout linear regulators from Micrel are rated to a

maximum junction temperature of 125°C. It is important not to

exceed this maximum junction temperature during operation

of the device. To prevent this maximum junction temperature

from being exceeded, the appropriate ground plane heat sink

must be used.

JA



JC CA

printed circuit board

ground plane

heat sink area

MSOP-8

AMBIENT

Figure 3. Thermal Resistance

Figure 4 shows copper area versus power dissipation with

each trace corresponding to a different temperature rise

above ambient.

From these curves, the minimum area of copper necessary for

the part to operate safely can be determined. The maximum

allowable temperature rise must be calculated to determine

operation along which curve.

ΔT = TJ(max) – TA(max)

TJ(max) = 125°C

Figure 4. Copper Area vs. Power-MSOP

Power Dissipation (∆TJA)

Figure 5. Copper Area vs. Power-MSOP

Power Dissipation (TA)

February 2005 11 MIC3975

MIC3975 Micrel

TA(max) = maximum ambient operating temperature

For example, the maximum ambient temperature is 50°C,

the ΔT is determined as follows:

ΔT = 125°C – 50°C

ΔT = 75°C

Using Figure 4, the minimum amount of required copper can

be determined based on the required power dissipation. Power

dissipation in a linear regulator is calculated as follows:

PD = (VIN – VOUT) IOUT + VIN × IGND

If we use a 2.5V output device and a 3.3V input at an output

current of 750mA, then our power dissipation is as follows:

PD = (3.3V – 2.5V) × 750mA + 3.3V × 7.5mA

PD = 600mW + 25mW

PD = 625mW

From Figure 4, the minimum amount of copper required to

operate this application at a ΔT of 75°C is 160mm2.

Quick Method

Determine the power dissipation requirements for the design

along with the maximum ambient temperature at which the

device will be operated. Refer to Figure 5, which shows safe

operating curves for three different ambient temperatures:

25°C, 50°C and 85°C. From these curves, the minimum

amount of copper can be determined by knowing the maxi-

mum power dissipation required. If the maximum ambient

temperature is 50°C and the power dissipation is as above,

625mW, the curve in Figure 5 shows that the required area

of copper is 160mm2.

The θJA of this package is ideally 80°C/W, but it will vary

depending upon the availability of copper ground plane to

which it is attached.

MIC3975 Micrel

MIC3975 12 February 2005

Package Information

8-Lead 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 datasheet 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

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 at Purchaser’s own risk and Purchaser agrees to fully indemnify

Micrel for any damages resulting from such use or sale.