MIC79050-4.2YS - MICROCHIP TECHNOLOGY

 2017 Microchip Technology Inc. DS20005771A-page 1

MIC79050

Features

• High-Accuracy Charge Voltage: ±0.75% over

–5°C to + 60°C (Li-ion charging temperature

range)

• Zero Off-Mode Current

• 10 µA Reverse Leakage

• Ultra-Low 380 mV Dropout at 500 mA

• Wide Input Voltage Range

• Logic-Controlled Enable Input (8-Lead Devices

Only)

• Thermal Shutdown and Current-Limit Protection

• Power MSOP-8, Power SOIC-8, and SOT-223

Packages

• Pulse Charging Capability

Applications

• Li-Ion Battery Charger

• Cellular Phones

• Palmtop Computers

•PDAs

• Self-Charging Battery Packs

General Description

The MIC79050 is a simple single-cell lithium-ion battery

charger. It includes an on-chip pass transistor for high

precision charging. Featuring ultra-high precision

(±0.75% over the Li-ion battery charging temperature

range) and “zero” off-mode current, the MIC79050

provides a very simple, cost effective solution for

charging lithium-ion battery.

Other features of the MIC79050 include current-limit

and thermal shutdown protection. In the event the input

voltage to the charger is disconnected, the MIC79050

also provides minimal reverse-current and

reversed-battery protection.

The MIC79050 is a fixed 4.2V device and comes in the

thermally-enhanced MSOP-8, SOIC-8, and SOT-223

packages. The 8-lead versions also come equipped

with enable and feedback inputs. All versions are

specified over the temperature range of –40°C to

+125°C.

Package Types

MIC79050

3-Lead SOT-223 (S)

IN BAT

GND

132

TAB

GND

MIC79050

8-Lead SOIC/MSOP (M/MM)

GND

BAT

Simple Lithium-Ion Battery Charger

MIC79050

DS20005771A-page 2  2017 Microchip Technology Inc.

Typical Application Circuits

Functional Block Diagrams

Li-Ion

Cell

4.2V 0.75% over Temp

IN BAT

GND

MIC79050-4.2YS

Regulated or

unregulated

wall adapter

4.2V 0.75%

Li-Ion

Cell

IN BAT

GND

MIC79050-4.2YMM

External PWM*

*See Applications Information

Regulated or

unregulated

wall adapter

Simplest Battery Charging

Solution

Pulse-Charging

Application

Current Limit

Thermal Shutdown

GND

Bandgap

Ref.

BAT

MIC79050-4.2YS

3-Lead Version

GND

REF

Bandgap

Ref.

Current Limit

Thermal Shutdown

BAT

MIC79050-4.2YM/YMM

8-Lead Version

 2017 Microchip Technology Inc. DS20005771A-page 3

MIC79050

1.0 ELECTRICAL CHARACTERISTICS

Absolute Maximum Ratings †

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

Power Dissipation (PD) (Note 1) ............................................................................................................ Internally Limited

Operating Ratings ‡

Supply Input Voltage (VIN) ......................................................................................................................... +2.5V to +16V

Enable Input Voltage (VEN) .................................................................................................................................0V to VIN

† Notice: Stresses above those listed under “Absolute Maximum Ratings” may cause permanent damage to the device.

This is a stress rating only and functional operation of the device at those or any other conditions above those indicated

in the operational sections of this specification is not intended. Exposure to maximum rating conditions for extended

periods may affect device reliability.

‡ Notice: The device is not guaranteed to function outside its operating ratings.

Note 1: The maximum allowable power dissipation at any TA (ambient temperature) is calculated using: PD(max) =

(TJ(max) – TA) ÷ θJA. Exceeding the maximum allowable power dissipation will result in excessive die tem-

perature, and the regulator will go into thermal shutdown.

TABLE 1-1: ELECTRICAL CHARACTERISTICS

Electrical Characteristics: VIN = VBAT + 1.0V; COUT = 4.7 μF, IOUT = 100 μA; TJ = +25°C, bold values indicate

–40°C ≤ TJ ≤ +125°C; unless noted.

Parameter Symbol Min. Typ. Max. Units Conditions

Battery Voltage Accuracy VBAT –0.75 — 0.75 % Variation from nominal VOUT

, –5°C

to +60°C

Battery Voltage Temperature

Coefficient

∆VBAT/

∆T—40 —ppm/°CNote 1

Line Regulation ∆VBAT/

VBAT

— 0.009 0.05 %/V VIN = VBAT + 1V to 16V

——0.1

Load Regulation ∆VBAT/

VBAT

— 0.05 0.5 %I

OUT = 100 μA to 500 mA, Note 2

——0.7

Dropout Voltage (Note 3)VIN –

VBAT

—380500 mV IOUT = 500 mA

——600

Ground Pin Current (Note 4,

Note 5)IGND

—85130µA VEN ≥ 3.0V, IOUT = 100 μA

——170

—1120 mA VEN ≥ 3.0V, IOUT = 500 mA

——25

Ground Pin Quiescent

Current (Note 5)IGND

—0.05 3µA VEN ≤ 0.4V (shutdown)

—0.10 8VEN ≤ 0.18V (shutdown)

Ripple Rejection PSRR — 75 — dB f = 120 Hz

Current Limit ILIMIT

—750 900 mA VBAT = 0V

——1000

Thermal Regulation ∆VBAT/

∆PD

—0.05— %/WNote 6

ENABLE Input

Enable Input Logic-Low

Voltage VENL

—0.4—

VVEN = logic-low (shutdown)

——0.18

2.0 —— V

EN = logic-high (enabled)

MIC79050

DS20005771A-page 4  2017 Microchip Technology Inc.

Enable Input Current IENL

—0.01–1 µA VENL ≤ 0.4V (shutdown)

—0.01 –2 VENL ≤ 0.18V (shutdown)

—I

ENH

—520µA VENH ≥ 2.0V (enabled)

——25

Note 1: Battery voltage temperature coefficient is the worst case voltage change divided by the total temperature

range.

2: Regulation is measured at constant junction temperature using low duty cycle pulse testing. Parts are

tested for load regulation in the load range from 100 μA to 500 mA. Changes in output voltage due to heat-

ing effects are covered by the thermal regulation specification.

3: Dropout voltage is defined as the input to battery output differential at which the battery voltage drops 2%

below its nominal value measured at 1V differential.

4: Ground pin current is the charger quiescent current plus pass transistor base current. The total current

drawn from the supply is the sum of the load current plus the ground pin current.

5: VEN is the voltage externally applied to devices with the EN (enable) input pin. MSOP-8 (MM) and SOIC-8

(M) packages only.

6: Thermal regulation is the change in battery voltage at a time “t” after a change in power dissipation is

applied, excluding load or line regulation effects. Specifications are for a 500 mA load pulse at VIN = 16V

for t = 10 ms.

TABLE 1-1: ELECTRICAL CHARACTERISTICS (CONTINUED)

Electrical Characteristics: VIN = VBAT + 1.0V; COUT = 4.7 μF, IOUT = 100 μA; TJ = +25°C, bold values indicate

–40°C ≤ TJ ≤ +125°C; unless noted.

Parameter Symbol Min. Typ. Max. Units Conditions

 2017 Microchip Technology Inc. DS20005771A-page 5

MIC79050

TEMPERATURE SPECIFICATIONS (Note 1)

Parameters Sym. Min. Typ. Max. Units Conditions

Temperature Ranges

Junction Operating Temperature

Range

TJ–40 — +125 °C —

Storage Temperature Range TS–65 — +150 °C —

Lead Temperature — — — +260 °C Soldering, 5s

Package Thermal Resistances (Note 2)

Thermal Resistance MSOP-8 JA —80 —°C/W—

Thermal Resistance SOIC-8 JA —63 —°C/W—

Thermal Resistance SOT-223 JC —15 —°C/W—

JA —62 —°C/W—

Note 1: The maximum allowable power dissipation is a function of ambient temperature, the maximum allowable

junction temperature and the thermal resistance from junction to air (i.e., TA, TJ, JA). Exceeding the

maximum allowable power dissipation will cause the device operating junction temperature to exceed the

maximum +125°C rating. Sustained junction temperatures above +125°C can impact the device reliability.

2: The maximum allowable power dissipation at any TA (ambient temperature) is calculated using: PD(max) =

(TJ(max) – TA) ÷ θJA. Exceeding the maximum allowable power dissipation will result in excessive die tem-

perature, and the regulator will go into thermal shutdown.

MIC79050

DS20005771A-page 6  2017 Microchip Technology Inc.

2.0 TYPICAL PERFORMANCE CURVES

FIGURE 2-1: Dropout Voltage vs. Output

Current.

FIGURE 2-2: Dropout Voltage vs.

Temperature.

FIGURE 2-3: Dropout Characteristics.

FIGURE 2-4: Dropout Characteristics.

FIGURE 2-5: Output Current vs. Ground

Current.

FIGURE 2-6: Ground Current vs. Supply

Voltage.

Note: The graphs and tables provided following this note are a statistical summary based on a limited number of

samples and are provided for informational purposes only. The performance characteristics listed herein

are not tested or guaranteed. In some graphs or tables, the data presented may be outside the specified

operating range (e.g., outside specified power supply range) and therefore outside the warranted range.

100

200

300

400

0 100 200 300 400 500

DROPOUT VOLTAGE (mV)

OUTPUT CURRENT (mA)

100

200

300

400

500

600

-40 0 40 80 120

DROPOUT VOLTAGE (mV)

TEMPERATURE (°C)

0246810121416

OUTPUT VOLTAGE (V)

INPUT VOLTAGE (V)

50mA,150mA

5mA

0246

OUTPUT VOLTAGE (V)

INPUT VOLTAGE (V)

250mA

500mA

0 100 200 300 400 500

GROUND CURRENT (mA)

OUTPUT CURRENT (mA)

0.5

1.5

0 4 8 12 16

GROUND CURRENT (mA)

SUPPLY VOLTAGE (V)

50mA

5mA

 2017 Microchip Technology Inc. DS20005771A-page 7

MIC79050

FIGURE 2-7: Ground Current vs. Supply

Voltage.

FIGURE 2-8: Ground Current vs.

Temperature.

FIGURE 2-9: Ground Current vs.

Temperature.

FIGURE 2-10: Ground Current vs.

Temperature.

FIGURE 2-11: Battery Voltage vs.

Temperature.

FIGURE 2-12: Short-Circuit Current vs.

Temperature.

0123456

GROUND CURRENT (mA)

SUPPLY VOLTAGE (V)

500mA

250mA

125mA

100

150

-40 0 40 80 120

GROUND CURRENT (μA)

TEMPERATURE (°C)

3.0

3.2

3.4

3.6

3.8

4.0

-40 0 40 80 120

GROUND CURRENT (mA)

TEMPERATURE (°C)

11.0

11.5

12.0

12.5

13.0

13.5

-40 0 40 80 120

GROUND CURRENT (mA)

TEMPERATURE (°C)

4.190

4.195

4.200

4.205

4.210

-40 -20 0 20 40 60 80 100120140

OUTPUT VOLTAGE (V)

TEMPERATURE (°C)

100

200

300

400

500

600

700

800

-40 0 40 80 120

SHORT CIRCUIT CURRENT (mA)

TEMPERATURE (°C)

MIC79050

DS20005771A-page 8  2017 Microchip Technology Inc.

FIGURE 2-13: Typical Voltage Drift Limits

vs. Time.

FIGURE 2-14: Reverse Leakage Current

vs. Output Voltage.

FIGURE 2-15: Reverse Leakage Current

vs. Output Voltage.

FIGURE 2-16: Reverse Leakage Current

vs. Temperature.

-0.75

-0.25

0.25

0.75

0 200 400 600 800

DRIFT FROM NOMINAL VOUT (%)

TIME (hrs)

Lower

012345

REVERSE LEAKAGE CURRENT (μA)

OUTPUT VOLTAGE (V)

-5 5 1525354555

REVERSE LEAKAGE CURRENT (μA)

TEMPERATURE (°C)

3.0V

3.6V

4.2V

VIN+VEN

FLOATING

-5 5 1525354555

REVERSE LEAKAGE CURRENT (μA)

TEMPERATURE (°C)

3.0V

3.6V

4.2V

VIN+VEN

GROUNDED

 2017 Microchip Technology Inc. DS20005771A-page 9

MIC79050

3.0 PIN DES CRIPTIONS

The descriptions of the pins are listed in Table 3-1.

TABLE 3-1: PIN FUNCTION TABLE

Pin Number

SOT-223

Pin Number

SOIC-8,

MSOP-8 Pin Name Description

1 2 IN Supply input.

2, TAB 5, 6, 7, 8 GND Ground: SOT-223 pin 2 and TAB are internally connected. SOIC-8

pins 5 through 8 are internally connected.

3 3 BAT Battery voltage output.

— 1 EN Enable (Input): TTL/CMOS-compatible control input. Logic-high =

enable; logic-low or open = shutdown.

— 4 FB Feedback node.

MIC79050

DS20005771A-page 10  2017 Microchip Technology Inc.

4.0 FUNCTIONAL DESCRIPTION

The MIC79050 is a high-accuracy, linear battery

charging circuit designed for the simplest

implementation of a single lithium-ion (Li-ion) battery

charger. The part can operate from a regulated or

unregulated power source, making it ideal for various

applications. The MIC79050 can take an unregulated

voltage source and provide an extremely accurate

termination voltage. The output voltage varies only

0.75% from nominal over the standard temperature

range for Li-ion battery charging (–5°C to +60°C). With

a minimum of external components, an accurate

constant-current charger can be designed to provide

constant-current, constant-voltage charging for Li-ion

cells.

4.1 Input Voltage

The MIC79050 can operate with an input voltage up to

16V (20V absolute maximum), ideal for applications

where the input voltage can float high, such as an

unregulated wall adapter that obeys a load-line. Higher

voltages can be sustained without any performance

degradation to the output voltage. The line regulation of

the device is typically 0.009%/V; that is, a 10V change

on the input voltage corresponds to a 0.09% change in

output voltage.

4.2 Enable

The MIC79050 has an enable pin that allows the

charger to be disabled when the battery is fully charged

and the current drawn by the battery has approached a

minimum and/or the maximum charging time has timed

out. When disabled, the regulator output sinks a

minimum of current with the battery voltage applied

directly onto the output. This current is typically 12 μA

or less.

4.3 Feedback

The feedback pin allows for external manipulation of

the control loop. This node is connected to an external

resistive divider network, which is connected to the

internal error amplifier. This amplifier compares the

voltage at the feedback pin to an internal voltage

reference. The loop then corrects for changes in load

current or input voltage by monitoring the output

voltage and linearly controlling the drive to the large,

PNP pass element. By externally controlling the

voltage at the feedback pin the output can be disabled

or forced to the input voltage. Pulling and holding the

feedback pin low forces the output low. Holding the

feedback pin high forces the pass element into

saturation, where the output will be the input minus the

saturation (dropout) voltage.

4.4 Battery Output

The BAT pin is the output of the MIC79050 and

connects directly to the cell to provide charging current

and voltage. When the input is left floating or grounded,

the BAT pin limits reverse current to <12 μA to minimize

battery drain.

 2017 Microchip Technology Inc. DS20005771A-page 11

MIC79050

5.0 APPLICATIONS INFORMATION

5.1 Simple Lithium-Ion Battery

Charger

Figure 5-1 shows a simple, complete lithium-ion

battery charger. The charging circuit comprises of a

cheap wall adapter, with a load-line characteristic. This

characteristic is always present with cheap adapters

due to the internal impedance of the transformer

windings. The load-line of the unregulated output

should be less than 4.4V to 4.6V at somewhere

between 0.5C to 1C of the battery under charge. This

4.4 to 4.6V value is an approximate number based on

the headroom needed above 4.2V for the MIC79050 to

operate correctly. In other words, for a 500 mAh

battery, the output of the semi-regulated supply should

be between 225 mA to 500 mA (0.5C to 1C). If it is

below 225 mA no damage will occur but the battery will

take longer to charge. Figure 5-2 shows a typical wall

adapter characteristic with an output current of 350 mA

at 4.5V. This natural impedance of the wall adapter will

limit the maximum current into the battery, so no

external circuitry is needed to accomplish this.

If extra impedance is needed to achieve the desired

load-line, extra resistance can easily be added in series

with the MIC79050 IN pin.

FIGURE 5-1: Load-Line Charger with End-of-Charge Termination Circuit.

FIGURE 5-2: Load-Line Characteristics of

AC Wall Adapter.

5.2 The Charging Cycle

See Figure 5-3.

State A: Initial charge. Here the battery’s charging

current is limited by the wall adapter’s natural

impedance. The battery voltage approaches 4.2V.

State B: Constant voltage charge. Here the battery

voltage is at 4.2V ±0.75% and the current is decaying

in the battery. When the battery has reached

approximately 1/10th of its 1C rating, the battery is

considered to have reached full charge. Because of the

natural characteristic impedance of the cheap wall

adapters, as the battery current decreases so the input

voltage increases. The MIC6270 and the LM4041 are

configured as a simple voltage monitor, indicating when

the input voltage has reached such a level so the

current in the battery is low, indicating full charge.

State C: End of charge cycle. When the input voltage,

VS reaches VEOC, an end of charge signal is indicated.

State D: Top up charge. As soon as enough current is

drawn out of the input source, which pulls the voltage

lower than the VEOC, the end of charge flag will be

pulled low and charging will initiate.

Variations on this scheme can be implemented, such

as the circuit shown in Figure 5-4.

For those designs that have a zero impedance source,

see Figure 5-5.

LM4041

CIM3-1.2

IN BAT

GND

MIC79050-4.2YM

EOC

= V

REF

(1+ )

Impedance

AC Load-line Wall Adapter

10k 4.7μF

End of Charge

MIC6270

VREF = 1.225V

0 0.2 0.4 0.6 0.8

SOURCE VOLTAGE (V)

SOURCE CURRENT (A)

MIC79050

DS20005771A-page 12  2017 Microchip Technology Inc.

FIGURE 5-3: Charging Cycles.

FIGURE 5-4: Protected Constant-Current Charger.

5.3 Protected Constant-Current

Charger

Another form of charging is using a simple wall adapter

that offers a fixed voltage at a controlled, maximum

current rating. The output of a typical charger will

source a fixed voltage at a maximum current unless

that maximum current is exceeded. In the event that

the maximum current is exceeded, the voltage will drop

while maintaining that maximum current. Using an

MIC79050 after this type of charger is ideal for

lithium-ion battery charging. The only obstacle is end of

charger termination. Using a simple differential

amplifier and a similar comparator and reference

circuit, similar to Figure 5-1, completes a single cell

lithium-ion battery charger solution.

Figure 5-4 shows this solution in completion. The

source is a fixed 5V source capable of a maximum of

400 mA of current. When the battery demands full

current (fast charge), the source will provide only

400 mA and the input will be pulled down. The output

of the MIC79050 will follow the input minus a small

voltage drop. When the battery approaches full charge,

the current will taper off. As the current across RS

approaches 50 mA, the output of the differential

amplifier (MIC7300) will approach 1.225V, the

reference voltage set by the LM4041. When it drops

below the reference voltage, the output of the

comparator (MIC6270) will allow the base of Q1 to be

pulled high through R2.

VEOC

Open Circuit

Charger Voltage

Battery Current (IB)

Battery Voltage (VB)

Unregulated Input

Voltage(VB)

79050 Programmed

Output Voltage

(No LoadVoltage)

End of Charge (V

EOC

)

State A

Initial Charge

State B

Voltage Charge

State C

End of Charge

State D

Charge Top

State C

IN BAT

GND

MIC79050-4.2YM

LM4041

CIM3-1.2

5V 5%@

400mA 5%

4.7μF

8.06M

47k



10k

MIC6270

MIC7300

10k

Li-Ion

Cell

 2017 Microchip Technology Inc. DS20005771A-page 13

MIC79050

5.4 Zero-Output Impedance Source

Charging

Input voltage sources that have very low output

impedances can be a challenge due to the nature of the

source. Using the circuit in Figure 5-5 will provide a

constant-current and constant voltage charging

algorithm with the appropriate end-of-charge

termination. The main loop consists of an op-amp

controlling the feedback pin through the schottky diode,

D1. The charge current through RS is held constant by

the op-amp circuit until the output draws less than the

set charge-current. At this point, the output goes

constant-voltage. When the current through RS gets to

less than 50 mA, the difference amp output becomes

less than the reference voltage of the MIC834 and the

output pulls low. This sets the output of the MIC79050

less than nominal, stopping current flow and

terminating charge.

FIGURE 5-5: Zero-Output Impedance Source Charging.

5.5 Lithium-Ion Battery Charging

Single lithium-ion cells are typically charged by

providing a constant current and terminating the charge

with constant voltage. The charge cycle must be

initiated by ensuring that the battery is not in deep

discharge. If the battery voltage is below 2.5V, it is

commonly recommended to trickle charge the battery

with 5 mA to 10 mA of current until the output is above

2.5V. At this point, the battery can be charged with

constant current until it reaches its top off voltage (4.2V

for a typical single lithium-ion cell) or a time-out occurs.

For the constant-voltage portion of the charging circuit,

an extremely accurate termination voltage is highly

recommended. The higher the accuracy of the

termination circuit, the more energy the battery will

store. Because lithium-ion cells do not exhibit a

memory effect, less accurate termination does not

harm the cell, but simply stores less usable energy in

the battery. The charge cycle is completed by disabling

the charge circuit after the termination current drops

below a minimum recommended level, typically 50 mA

or less, depending on the manufacturer’s

recommendation, or if the circuit times out.

5.6 Time-Out

The time-out aspect of lithium-ion battery charging can

be added as a safety feature of the circuit. Often times

this function is incorporated in the software portion of

an application using a real-time clock to count out the

maximum amount of time allowed in the charging cycle.

When the maximum recommended charge time for the

specific cell has been exceeded, the enable pin of the

MIC79050 can be pulled low, and the output will float to

the battery voltage, no longer providing current to the

output.

As a second option, the feedback pin of the MIC79050

can be modulated as in Figure 5-6. It shows a simple

circuit where the MIC834, an integrated comparator

and reference, monitors the battery voltage and

disables the MIC79050 output after the voltage on the

battery exceeds a set value. When the voltage decays

below this set threshold, the MIC834 drives Q1 low

allowing the MIC79050 to turn on again and provide

current to the battery until it is fully charged. This form

of pulse charging is an acceptable way of maintaining

the full charge on a cell until it is ready to be used.

MIC79050-4.2YM

MIC834

SD101

MIC7122

IN BAT

GND

8.06M

4.7μF

R2=124k

R3=1k

R4=124k

0.01μF

VDD OUT

GNDINP

=1k

221k

16.2k

16k

10k

5V R



ICC=80mV

RSIEOC

1.24V × R

× R

LM4041

CIM3-1.2

Li-Ion

Cell

MIC79050

DS20005771A-page 14  2017 Microchip Technology Inc.

FIGURE 5-6: Pulse Charging for Top-Off

Voltage.

5.7 Charging Rate

Lithium-ion cells are typically charged at rates that are

fractional multiples of their rated capacity. The

maximum varies between 1C and 1.3C (1× to 1.3× the

capacity of the cell). The MIC79050 can be used for

any cell size. The size of the cell and the current

capability of the input source will determine the overall

circuit charge rate. For example, a 1200 mAh battery

charged with the MIC79050 can be charged at a

maximum of 0.5C. There are no adverse effects to

charging at lower charge rates; that charging will just

take longer. Charging at rates greater than 1C are not

recommended, nor do they decrease the charge time

linearly.

The MIC79050 is capable of providing 500 mA of

current at its nominal rated output voltage of 4.2V. If the

input is brought below the nominal output voltage, the

output will follow the input, less the saturation voltage

drop of the pass element. If the cell draws more than

the maximum output current of the device, the output

will be pulled low, charging the cell at 600 mA to

700 mA current. If the input is a fixed source with a low

output impedance, this could lead to a large drop

across the MIC79050 and excess heating. By driving

the feedback pin with an external PWM circuit, the

MIC79050 can be used to pulse charge the battery to

reduce power dissipation and bring the device and the

entire unit down to a lower operating temperature.

Figure 5-7 and Figure 5-8 show typical configurations

for PWM-based pulse-charging topologies. Figure 5-7

uses an external PWM signal to control the charger,

while Figure 5-8 uses the MIC4417 as a low duty cycle

oscillator to drive the base of Q1. Consult the battery

manufacturer for optimal pulse-charging techniques.

FIGURE 5-7: External PWM Circuit

Design.

FIGURE 5-8: PWM-Based Pulse

Charging Using an MIC4417.

Figure 5-9 shows another application to increase the

output current capability of the MIC79050. By adding

an external PNP power transistor, higher output current

can be obtained while maintaining the same accuracy.

The internal PNP now becomes the driver of a

darlington array of PNP transistors, obtaining much

higher output currents for applications where the

charge rate of the battery is much higher.

FIGURE 5-9: High-Current Charging.

5.8 Regulated Input Source Charging

When providing a constant-current, constant-voltage,

charger solution from a well-regulated adapter circuit,

the MIC79050 can be used with external components

to provide a constant voltage, constant-current charger

solution. Figure 5-10 shows a configuration for a

high-side battery charger circuit that monitors input

current to the battery and allows a constant current

charge that is accurately terminated with the

MIC79050. The circuit works best with smaller

batteries, charging at C rates in the 300 mA to 500 mA

range. The MIC7300 op-amp compares the drop

across a current sense resistor and compares that to a

high-side voltage reference, the LM4041, pulling the

feedback pin low when the circuit is in the

Li-Ion

Cell

IN BAT

GND

MIC79050-4.2YMM

VDD OUT

GNDINP

R1100k

4.7μF

MIC834

VIN

GND

REF

=1.240V

BAT(low)

= V

REF

(1+ )

Li-Ion

Cell

4.7μF

IN BAT

GND

MIC79050-4.2YMM

VIN

External PWM

Li-Ion

Cell

4.7μF

200pF

40k

IN BAT

GND

MIC79050-4.2YMM

VIN=4.5V to 16V

MIC4417

IN BAT 4.7μF

GND

MIC79050-4.2YMM

 2017 Microchip Technology Inc. DS20005771A-page 15

MIC79050

constant-current mode. When the current through the

resistor drops and the battery gets closer to full charge,

the output of the op-amp rises and allows the internal

feedback network of the regulator take over, regulating

the output to 4.2V.

FIGURE 5-10: Constant-Current,

Constant-Voltage Charger.

5.9 Simple Charging

The MIC79050 is available in a three-terminal package,

allowing for extremely simple battery charging. When

used with a current-limited, low-power input supply, the

MIC79050-4.2YS completes a very simple,

low-charge-rate, battery-charger circuit. It provides the

accuracy required for termination, while a

current-limited input supply offers the constant-current

portion of the algorithm.

5.10 Thermal Considerations

The MIC79050 is offered in three packages for the

various applications. The SOT-223 is most thermally

efficient of the three packages, with the power SOIC-8

and the power MSOP-8 following suit.

5.10.1 POWER SOIC-8 THERMAL

CHARACTERISTICS

One of the secrets of the MIC79050’s performance is

its power SOIC-8 package that features half the

thermal resistance of a standard SOIC-8 package.

Lower thermal resistance means more output current

or higher input voltage for a given package 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,

or thermal resistance junction to case and θCA, thermal

resistance case to ambient (Figure 5-11). 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, thermal resistance case to sink, and

θSA, thermal resistance sink to ambient. Using the

power SOIC-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 capability of the device. Typically, the power

SOIC-8 has a θJC of 20°C/W, this is significantly lower

than the standard SOIC-8, which is typically 75°C/W.

θCA is reduced because pins 5-8 can now be soldered

directly to a ground plane, which significantly reduces

the case to sink thermal resistance and sink to ambient

thermal resistance.

FIGURE 5-11: Thermal Resistance.

The MIC79050 is 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.

Figure 5-12 shows curves of copper area versus power

dissipation, each trace corresponding to different

temperature rises 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.

FIGURE 5-12: Copper Area vs. Power

SOIC Power Dissipation (∆TJA).

IN BAT

GND

MIC79050-4.2YMM

SD101

4.7μF

0.01μF

MIC7300

LM4041CIM3-1.2

16.2k

221k

10k

ImV

== 80

șJA

JC șCA

Printed Circuit Board

Ground Plane

Heat Sink Area

SOIC-8

AMBIENT

100

200

300

400

500

600

700

800

900

0 0.25 0.50 0.75 1.00 1.25 1.50

COPPER AREA (mm )

POWER DISSIPATION (W)

¨TJA =

MIC79050

DS20005771A-page 16  2017 Microchip Technology Inc.

∆T is calculated by taking the maximum junction

temperature and subtracting the maximum ambient

operating temperature.

For example, if the maximum ambient temperature is

+40°C, the ∆T is determined as follows:

EQUATION 5-1:

Using Figure 5-12, 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:

EQUATION 5-2:

For example, using the charging circuit in Figure 5-10,

assume the input is a fixed 5V and the output is pulled

down to 4.2V at a charge current of 500 mA. The power

dissipation in the MIC79050 is calculated as follows:

EQUATION 5-3:

From Figure 5-12, the minimum amount of copper

required to operate this application at a ∆T of +85°C is

less than 50 mm2.

5.10.2 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 5-13, 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 maximum

power dissipation required. If the maximum ambient

temperature is +40°C and the power dissipation is as

above, 0.46W, the curve in Figure 5-13 shows that the

required area of copper is 50 mm2.

The θJA of this package is ideally 63°C/W, but it will

vary depending upon the availability of copper ground

plane to which it is attached.

FIGURE 5-13: Copper Area vs. Power

SOIC Power Dissipation (TA).

5.10.3 POWER MSOP-8 THERMAL

CHARACTERISTICS

The power MSOP-8 package follows the same idea as

the power SOIC-8 package, using four ground leads

with the die-attach paddle to create a single-piece

electrical and thermal conductor, reducing thermal

resistance and increasing power dissipation capability.

The same method of determining the heat sink area

used for the power SOIC-8 can be applied directly to

the power MSOP-8. The same two curves showing

power dissipation versus copper area are reproduced

for the power-MSOP-8 and they can be applied

identically.

5.10.4 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 5-15, 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 maximum

power dissipation required. If the maximum ambient

temperature is +25°C and the power dissipation is 1W,

the curve in Figure 5-15 shows that the required area

of copper is 500 mm2, when using the power MSOP-8.

T125C=40C85C=–

PDVIN VOUT

–IOUT VIN IGND

+=

PD5V4.2V–0.5A5V0.012A0.460W=+=

100

200

300

400

500

600

700

900

0 0.25 0.50 0.75 1.00 1.25 1.50

COPPER AREA (mm )

POWER DISSIPATION (W)

85°C

50°C

25°C

TJ= 125°C

 2017 Microchip Technology Inc. DS20005771A-page 17

MIC79050

FIGURE 5-14: Copper Area vs. Power

MSOP Power Dissipation (∆TJA).

FIGURE 5-15: Copper Area vs. Power

MSOP Power Dissipation (TA).

100

200

300

400

500

600

700

800

900

0 0.25 0.50 0.75 1.00 1.25 1.50

COPPER AREA (mm )

POWER DISSIPATION (W)

100

200

300

400

500

600

700

800

900

0 0.25 0.50 0.75 1.00 1.25 1.50

COPPER AREA (mm )

POWER DISSIPATION (W)

85°C

50°C

25°C

TJ= 125°C

MIC79050

DS20005771A-page 18  2017 Microchip Technology Inc.

6.0 PACKAGING INFORMATION

6.1 Package Marking Information

Example3-Lead SOT-223*

Example8-Lead SOIC*

XXXXX

X.XYNNNP

79050

4.2Y604P

XXXXX

-X.XXX

WNNN

79050

-4.2YM

9626

XXXXX

-X.XY

Example8-Lead MSOP*

79050

-4.2Y

Legend: XX...X Product code or customer-specific information

Y Year code (last digit of calendar year)

YY Year code (last 2 digits of calendar year)

WW Week code (week of January 1 is week ‘01’)

NNN Alphanumeric traceability code

Pb-free JEDEC® designator for Matte Tin (Sn)

*This package is Pb-free. The Pb-free JEDEC designator ( )

can be found on the outer packaging for this package.

●, ▲, ▼Pin one index is identified by a dot, delta up, or delta down (triangle

mark).

Note: In the event the full Microchip part number cannot be marked on one line, it will

be carried over to the next line, thus limiting the number of available

characters for customer-specific information. Package may or may not include

the corporate logo.

Underbar (_) and/or Overbar (⎯) symbol may not be to scale.

 2017 Microchip Technology Inc. DS20005771A-page 19

MIC79050

3-Lead SOT-223 Package Outline and Recommended Land Pattern

Note: For the most current package drawings, please see the Microchip Packaging Specification located at

http://www.microchip.com/packaging.

MIC79050

DS20005771A-page 20  2017 Microchip Technology Inc.

8-Lead SOIC Package Outline and Recommended Land Pattern

Note: For the most current package drawings, please see the Microchip Packaging Specification located at

http://www.microchip.com/packaging.

 2017 Microchip Technology Inc. DS20005771A-page 21

MIC79050

8-Lead MSOP Package Outline and Recommended Land Pattern

Note: For the most current package drawings, please see the Microchip Packaging Specification located at

http://www.microchip.com/packaging.

MIC79050

DS20005771A-page 22  2017 Microchip Technology Inc.

NOTES:

 2017 Microchip Technology Inc. DS20005771A-page 23

MIC79050

APPENDIX A: REVISION HISTORY

Revision A (July 2017)

• Converted Micrel document MIC79050 to Micro-

chip data sheet DS20005771A.

• Minor text changes throughout.

MIC79050

DS20005771A-page 24  2017 Microchip Technology Inc.

NOTES:

 2017 Microchip Technology Inc. DS20005771A-page 25

MIC79050

PRODUCT IDENTIFICATION SYSTEM

To order or obtain information, e.g., on pricing or delivery, contact your local Microchip representative or sales office.

Examples:

a) MIC79050-4.2YS: Simple Lithium-Ion Battery