MIC68400YML TR - MICROCHIP TECHNOLOGY

 2017 Microchip Technology Inc. DS20005824A-page 1

MIC68400

Features

• Stable with 10 µF Ceramic Capacitor

• Input Voltage Range: 1.65V to 5.5V

• 0.5V Reference

• ±2.0% Output Tolerance over Temperature

• 4A Maximum Output Current – Peak Start-Up

• 3A Continuous Operating Current

• Tracking on Turn-On and Turn-Off with Pin

Strapping

• Timing Controlled Sequencing On/Off

• Programmable Ramp Control for In-Rush Current

Limiting and Slew Rate Control of the Output

Voltage During Turn-On and Turn-Off

• Power-On Reset (POR) Supervisor with

Programmable Delay Time

• Single Master can Control Multiple Slave

Regulators with Tracking Output Voltages

• Tiny 4 mm x 4 mm QFN Package

• Maximum Dropout (VIN – VOUT) of 500 mV over

Temperature at 3A Output Current

• Fixed and Adjustable Output Voltages

• Excellent Line and Load Regulation Specifications

• Logic Controlled Shutdown

• Thermal Shutdown and Current-Limit Protection

Applications

• FPGA/PLD Power Supply

• Networking/Telecom Equipment

• Microprocessor Core Voltage

• High Efficiency Linear Post Regulator

• Sequenced or Tracked Power Supply

General Description

The MIC68400 is a high peak current LDO regulator

designed specifically for powering applications such as

FPGA core voltages that require high start up current

with lower nominal operating current. Capable of

sourcing 4A of current for start-up, the MIC68400

provides high power from a small QFN leadless

package. The MIC68400 can also implement a variety

of power-up and power-down protocols such as

sequencing, tracking, and ratiometric tracking.

The MIC68400 operates from a wide input range of

1.65V to 5.5V, which includes all of the main supply

voltages commonly available today. It is designed to

drive digital circuits requiring low voltage at high

currents (i.e. PLDs, DSP, microcontroller, etc.). The

MIC68400 incorporates a delay pin (Delay) for control

of power on reset output (POR) at turn-on and

power-down delay at turn-off. In addition there is a

ramp control pin (RC) for either tracking applications or

output voltage slew rate adjustment at turn-on and

turn-off. This is important in applications where the load

is highly capacitive and in-rush currents can cause

supply voltages to fail and microprocessors or other

complex logic chips to hang up.

Multiple MIC68400s can be daisy chained in two

modes. In tracking mode the output voltage of the

Master drives the RC pin of a Slave so that the Slave

tracks the main regulator during turn-on and turn-off. In

sequencing mode the POR of the Master drives the

enable (EN) of the Slave so that it turns on after the

Master and turns off before (or after) the Master. This

behavior is critical for power-up and power-down

control in multi-output power supplies. The MIC68400

is fully protected offering both thermal, current limit

protection, and reverse current protection.

The MIC68400 has a junction temperature range of

–40°C to +125°C and is available in fixed as well as an

adjustable option. The MIC68400 is offered in the tiny

16-pin 4 mm x 4 mm QFN package.

4A Sequencing LDO with Tracking and Ramp Control

MIC68400

DS20005824A-page 2  2017 Microchip Technology Inc.

Package Types

Typical Application Circuits

MIC68400, FIXED VOLTAGES

16-Lead QFN (ML)

MIC68400, ADJ. VOLTAGES

16-Lead QFN (ML)

13141516

8765

VIN

DELAY

VOUT

SNS

POR

VIN

VOUT

GND

13141516

8765

VIN

DELAY

VOUT

ADJ

POR

VIN

VOUT

GND

MIC68400

Sequenced Dual Power Supply for I/O and Core Voltage of µProcessor

10μF

1nF

= 3.3V

IN1 OUT1

EN1 SNS1

RC1

DLY1 POR1

μProcessor

I/O

CORE

/RESET

47k 47k

10nF

0.7nF

0.6nF

MIC68400-1.8YML

Master

MIC68400-1.5YML

Slave

IN2 OUT2

EN2 SNS2

RC2

DLY2 GND

GND

POR2

0.1μF

U1.EN

U1.RC

U1.DLY

U1.OUT

U2.EN = U1.POR

U2.RC

U2.DLY

U2.OUT

U2.POR

U1.TRC

U2.TRC2

U1.TDLY U1.TDLY

U2.TDLY U2.TDLY

U1 Fully Shut Down

U2 Fully Shut Down

 2017 Microchip Technology Inc. DS20005824A-page 3

MIC68400

Typical Application Circuits (Continued)

Functional Block Diagram

10μF

10nF

= 1.8V

IN1 OUT1

EN1

RC1

DLY1 POR1

μProcessor

I/O

CORE

/RESET

47k:

10nF

MIC68400-1.8YML

Master

MIC68400-1.2YML

Slave

IN2 OUT2

EN2 SNS2

SNS1

RC2

DLY2 GND POR2

0.1μF

MIC68400

Tracking Dual Power Supply for I/O and Core Voltage of µProcessor

U1.EN = U2.EN

U1.RC

U1.DLY

U2.RC = U1.OUT

U2.DLY

U2.OUT

U1.POR = U.2POR

U1.T

U2.T

DLY

U.2T

DLY

U1 Fully Shut Down

U2 Fully Shut Down

Bandgap

Reference

Output Error

Holdoff

Thermal

Shutdown

Low Voltage

Holdoff

Sequencing

Timer/Controller

BGStart

BGDis

Ramp

Control

RCDis

DLY BGStart: BandGap Startup

BGDis: BandGap Shutdown

RCDis: Ramp Control Discharge

GND

POR

SNS

OUT

Buffer

Error

Amp

Current

Driver

Current

Limit

External on

Adjustable Part

AMP

MIN

MIC68400

DS20005824A-page 4  2017 Microchip Technology Inc.

1.0 ELECTRICAL CHARACTERISTICS

Absolute Maximum Ratings †

Supply Voltage (VIN)....................................................................................................................................................+6V

Enable Input Voltage (VEN) .........................................................................................................................................+6V

POR (VPOR) ..................................................................................................................................................... VIN + 0.3V

RC .................................................................................................................................................................... VIN + 0.3V

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

Operating Ratings ‡

Supply Voltage (VIN)................................................................................................................................ +1.65V to +5.5V

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

Ramp Control (VRC) ....................................................................................................................................... 0V to +5.5V

† 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 of any TA (ambient temperature) is PD(MAX) = TJ(MAX) – TA)/JA.

Exceeding the maximum allowable power dissipation will result in excessive die temperature, and the reg-

ulator will go into thermal shutdown.

TABLE 1-1: ELECTRICAL CHARACTERISTICS

Electrical Characteristics: TA = +25°C with VIN = VOUT + 1V; VEN = VIN; IOUT = 10 mA; bold values indicate –40°C

 TJ  +125°C, unless noted. Note 1

Parameter Symbol Min. Typ. Max. Units Conditions

Output Voltage Accuracy –2 —2%10 mA < IOUT < IL(MAX), VOUT + 1 

VIN  5.5V

Feedback Voltage VFB 0.49 0.50 0.51 V Adjustable version only

Feedback Current IFB — 20 — nA Adjustable version only

Output Voltage Line

Regulation —0.060.5 %V

IN = VOUT + 1V to 5.0V

Output Voltage Load

Regulation —0.5 1%I

L = 10 mA to 3A

VIN – VO; Dropout Voltage

——400

IL = 1.5A

—300500 IL = 3.0A

—360800 IL = 4.0A

Ground Pin Current IGND

—1.2—

IL = 10 mA

—20— I

L = 1.5A

—55— I

L = 3.0A

—90130 IL = 4.0A

Shutdown Current ISHDN —0.0110 µA VEN = 0V; VOUT = 0V

Current Limit ILIMIT 4.0 6.0 — A VOUT = 0V; VIN = 3.0V

Start-Up Time tSU —35150 µs VEN = VIN; CRC = Open

Enable Input

Enable Input Threshold 1—— VRegulator enable

——0.2 Regulator shutdown

Enable Hysteresis 20 120 200 mV —

 2017 Microchip Technology Inc. DS20005824A-page 5

MIC68400

Enable Input Current —0.02— µA VIL  0.2V (Regulator shutdown)

—3— V

IH  1V (Regulator enable)

POR Output

POR Leakage Current IPOR(LEAK)

—— 1 µA VPOR = 5.5V; POR = High

—— 2

VPOR(LO) —6090 mV

Output Logic-Low Voltage

(undervoltage condition),

IPOR = 1 mA

VPOR

7.5 10 12.5

VOUT Ramping Up, Threshold,

Percent of VOUT below nominal

10 12.5 15 VOUT Ramping Down, Threshold,

Percent of VOUT below nominal

— 3 — Hysteresis

Delay Current IDELAY 0.7 11.3 µA VDELAY = 0.75V

Delay Voltage (Note 2)V

DELAY 1.185 1.235 1.285 VV

POR = High

Ramp Control

Ramp Control Current IRC 0.7 11.3 µA VRC = 0.75V

Output Discharge Current

(Note 3)IDC(OUT) 25 45 70 mA VOUT = 0.5VNOM, VRAMP =0V

Fixed Tracking Accuracy

(Note 4)–5025100 mV

200 mV < VRC < VTARGET; Measure

(VOUT – VRC)

Adjustable Tracking Accuracy

(Note 4)–10 15 50 mV Measure (VOUT – VRC x

(VTARGET/500 mV))

Note 1: Specification for packaged product only.

2: Timer High Voltage along with Delay pin current (1 µA nom.) determines the delay per µF of capacitance.

Typical delay is 1.1 sec/µF.

3: Discharge current is the current drawn from the output to ground to actively discharge the output capacitor

during the shutdown process.

4: VTARGET is the output voltage of an adjustable with customer resistor divider installed between VOUT and

ADJ/SNS pin, or the rated output voltage of a fixed device.

TABLE 1-1: ELECTRICAL CHARACTERISTICS (CONTINUED)

Electrical Characteristics: TA = +25°C with VIN = VOUT + 1V; VEN = VIN; IOUT = 10 mA; bold values indicate –40°C

 TJ  +125°C, unless noted. Note 1

Parameter Symbol Min. Typ. Max. Units Conditions

MIC68400

DS20005824A-page 6  2017 Microchip Technology Inc.

TEMPERATURE SPECIFICATIONS (Note 1)

Parameters Sym. Min. Typ. Max. Units Conditions

Tempe rature Ranges

Junction Temperature Range TJ–40 — +125 °C —

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

Package Thermal Resistances

Thermal Resistance 16-LD 4x4 QFN JA —30 —°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.

 2017 Microchip Technology Inc. DS20005824A-page 7

MIC68400

2.0 TYPICAL PERFORMANCE CURVES

FIGURE 2-1: Dropout Voltage vs.

Temperature.

FIGURE 2-2: Output Voltage vs. Input

Voltage.

FIGURE 2-3: Ground Current vs. Output

Current.

FIGURE 2-4: Dropout Voltage vs. Output

Current.

FIGURE 2-5: Current Limit vs. Input

Voltage.

FIGURE 2-6: Enable Threshold vs. Input

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.

MIC68400

DS20005824A-page 8  2017 Microchip Technology Inc.

FIGURE 2-7: Ground Current vs. Input

Voltage.

FIGURE 2-8: Output Voltage vs.

Temperature.

FIGURE 2-9: Ground Current vs.

Temperature.

FIGURE 2-10: Power Supply Rejection

Ratio.

FIGURE 2-11: Load Regulation.

FIGURE 2-12: Thermal Shutdown.

 2017 Microchip Technology Inc. DS20005824A-page 9

MIC68400

FIGURE 2-13: Enab le Turn-On.

FIGURE 2-14: Line Transient.

FIGURE 2-15: Load Transient.

MIC68400

DS20005824A-page 10  2017 Microchip Technology Inc.

3.0 PIN DESCRIPTIONS

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

TABLE 3-1: PIN FUNCTION TABLE

Pin Number Pin Name Description

1, 2, 15, 16 VIN Input: Input voltage supply pin. Place a capacitor to ground to bypass the input supply.

3 DELAY Delay: Capacitor to ground sets internal delay timer. Timer delays power-on reset

(POR) output at turn-on, and ramp down at turn-off.

4 RC Ramp Control: May be voltage driven for tracking applications or a capacitor to ground

will set the slew rate of output voltage during start-up.

5 EN Enable (Input): CMOS compatible input. Logic-high = enable, logic-low = shutdown.

6, 14 NC Not internally connected.

7, 8, Tab GND Ground.

9 POR Power-on Reset: Open-drain output device indicates when the output is in regulation.

High (open) means device is regulating within 10%. POR onset can be delayed using

a single capacitor from Delay to ground.

10 (Fixed) SNS Output Voltage Sense Pin: Connect directly to output pin.

10 (Adj.) ADJ Adjustable regulators: Feedback input. Connect to resistor voltage divider.

11, 12, 13 VOUT Output Voltage: Output of voltage regulator. Place capacitor to ground to bypass the

output voltage. Minimum load current is 100 µA. Nominal bypass capacitor is 10 µF.

 2017 Microchip Technology Inc. DS20005824A-page 11

MIC68400

4.0 APPLICATION INFORMATION

4.1 Enable Input

The MIC68400 features a TTL/CMOS-compatible

positive logic enable input for on/off control of the

device. High (>1V) enables the regulator while low

(<0.2V) disables the regulator. In shutdown, the

regulator consumes very little current (only a few

microamps of leakage). For simple applications, the

enable (EN) can be connected to VIN (IN). While

MIC68400 only requires a few microamps of enable

current to turn on, the actual enable pin current will

depend on the overdrive (enable voltage exceeding

1V) in each particular application.

FIGURE 4-1: Enable Connec tio ns for

Logic-Driven Input.

FIGURE 4-2: Enable Connec tio n for

VIN-Driven and/or Slow Rise Time Inputs.

If MIC68400 is used in standalone mode, it is not

recommended to connect the enable (EN) pin to the

input voltage supply (IN). In this case, the enable (EN)

input should be externally controlled, as indicated in the

Electrical Characteristics section (regulator enable for

VEN > 1.0V and regulator disable for VEN < 0.2V).

4.2 Input Capacitor

An input capacitor of 0.1 µF or greater is recommended

when the device is more than four inches away from

the bulk supply capacitance, or when the supply is a

battery. Small, surface-mount chip capacitors can be

used for bypassing. The capacitor should be placed

within one inch of the device for optimal performance.

Larger values will help to improve ripple rejection by

bypassing the regulator input, further improving the

integrity of the output voltage.

4.3 Output Capacitor

The MIC68400 requires an output capacitor for stable

operation. As a µCap LDO, the MIC68220 can operate

with ceramic output capacitors of 10 µF or greater with

ESR’s ranging from 3 m to over 300 m. Values

greater than 10 µF improve transient response and

noise reduction at high frequencies. X7R/X5R

dielectric-type ceramic capacitors are recommended

because of their superior temperature performance.

X7R-type capacitors change capacitance by 15% over

their operating temperature range and are the most

stable type of ceramic capacitors. Larger output

capacitances can be achieved by placing tantalum or

aluminum electrolytics in parallel with the ceramic

capacitor. For example, a 100 µF electrolytic in parallel

with a 10 µF ceramic can provide the transient and high

frequency noise performance of a 100 µF ceramic at a

significantly lower cost. Specific undershoot/overshoot

performance will depend on both the values and

ESR/ESL of the capacitors.

4.4 Adjustable Regulator Design

FIGURE 4-3: Adjustable Regulator with

Resistors.

The adjustable MIC68400 output voltage can be

programmed from 0.5V to 5.5V using a resistor divider

from output to the SNS pin. Resistors can be quite

large, up to 1 M because of the very high input

impedance and low bias current of the sense amplifier.

Typical sense input currents are less than 30 nA which

causes less than 0.3% error with R1 and R2 less than

or equal to 100 k. For large value resistors (>50 k)

OUT2

POR

1nF

= 3.3V

IN OUT

RC POR

SNS

EN DLY

47N

MIC68400-1.8YML

Master

MIC68400-1.5YML

Slave

IN SNS

OUT

RC POR

GND

DLY

0.1μF

10μF

10nF

47N

Control Logic

High > 1V

10μF

OUT1

10μF

1nF

= 3.3V

~1V/ms

IN OUT

SNS

RC POR

EN DLY

47.

MIC68400-1.8YML

Master

MIC68400-1.8YML

Slave

IN OUT

SNS

RC POR

GND

DLY

10nF

0.1μF

10μF

10nF

47.

N

OUT1

OUT2

POR

OUT

ADJ

0.5V

COUT

10μF

*CFF

0.1μF

*Required only for large

values of R1 and R2.

MIC68400

DS20005824A-page 12  2017 Microchip Technology Inc.

R1 should be bypassed by a small capacitor (CFF =

0.1 µF bypass capacitor) to avoid instability due to

phase lag at the ADJ/SNS input.

The output resistor divider values are calculated by:

EQUATION 4-1:

4.5 Power on Reset (POR) and Delay

(DLY)

The power-on reset output (POR) is an open-drain

N-Channel device requiring a pull-up resistor to either

the input voltage or output voltage for proper voltage

levels. POR is driven by the internal timer so that the

release of POR at turn-on can be delayed for as much

as one second. POR is always pulled low when enable

(EN) is pulled low or the output goes out of regulation

by more than 10% due to loading conditions.

The internal timer is controlled by the DLY pin which

has a bidirectional current source and two limiting

comparators. A capacitor connected from DLY to GND

sets the delay time for two functions. On start up, DLY

sets the time from the nominal output voltage is

reached to the release of the POR. At shut down, the

delay sets the time from disable (EN pin driven low) to

actual ramp down of the output voltage. The current

source is ±1 µA, which charges the capacitor from

~150 mV (nominal disabled DLY voltage) to ~1.25V. At

turn on, the DLY cap begins to charge when the output

voltage reaches 90% of the target value. When the

capacitor reaches 1.25V, the output of the POR is

released to go high. At turn off, the DLY cap begins to

discharge when the EN is driven low. When the cap

reaches ~150 mV the output is ramped down. Both

delays are nominally the same, and are calculated by

the same formula:

EQUATION 4-2:

The scale factor is 1.1 seconds/µF, 1.1 ms/nF, or

1.1 µs/pF. tDLYOFF is the time from lowering of EN to the

start of ramp down on the off cycle. TPOR is the time

from the rising of EN to the release (low to high edge)

of the POR. This behavior means that a µProcessor or

other complex logic system is guaranteed that the

nominal output voltage is stable for a known time

before the POR is released, and they are further

guaranteed that once POR is pulled low, they have a

known time to ‘tidy up’ memory or other registers for a

well-controlled shutdown. In Master/Slave

configurations, the timers can be used to ensure that

the Master is always accurately regulating when the

Slave is on.

4.6 Ramp Control

The ramp control (RC) has a bidirectional current

source and a sense amplifier, which together are used

to control the voltage at the output. When RC is below

the target voltage (nominal output voltage for fixed

voltage parts, 0.5V for adjustable parts) the RC pin

controls the output voltage. When RC is at or above the

target voltage, the output is controlled by the internal

regulator.

4.6.1 TRACKING APPLICATIONS:

DRIVING RC FROM A VOLTAGE

SOURCE

Fixed Parts: If RC is driven from another (Master)

regulator the two outputs will track each other until the

Master exceeds the target voltage of the Slave

regulator. Typically the output of the MIC68400 will

track above the RC input by 30 mV to 70 mV. This

offset is designed to allow Master/Slave tracking of

same-voltage regulators. Without the offset,

same-voltage Master/Slave configurations could suffer

poor regulation.

Adjustable Parts: The RC pin on adjustable versions

operates from 0V to 0.5V. To implement tracking on an

adjustable version, an external resistor divider must be

used. This divider is the nearly same ratio as the

voltage setting divider used to drive the SNS/ADJ pin.

It is recommended that the ratio be adjusted to track

~50 mV (2% to 3%) above the target voltage if the

Master and Slave are operating at the same target

voltage.

4.6.2 RAMP UP: CAP-CONTROLLED

SLEW RATE

If a capacitor is connected to RC, the bidirectional

current source will charge the cap during startup and

discharge the cap during shutdown. The size of the

capacitor and the RC current (1 µA nom.) control the

slew rate of the output voltage during startup. For

example, to ramp up a 1.8V regulator from zero to full

output in 10 ms requires a 5.6 nF capacitor.

VOUT 0.5VR1

-------1+





tDLY 1.1

CDLY

1A

-------------





 2017 Microchip Technology Inc. DS20005824A-page 13

MIC68400

For Fixed Versions:

EQUATION 4-3:

Similarly, to slew an adjustable (any output voltage)

from zero to full output in 10 ms requires a 20 nF cap.

For Adjustable Versions:

EQUATION 4-4:

4.6.3 RAMP DOWN: TURN OFF SLEW

RATE

When EN is lowered and the DLY pin has discharged,

the RC pin and the OUT pin slew toward zero. For fixed

voltage devices, the RC pin slew rate is 2 to 3 times the

SRON defined above. For adjustable voltage devices,

the RC pin slew is much higher. In both cases, turn off

slew rate may be determined by the RC pin for low

values of output capacitor, or by the maximum

discharge current available at the output for large

values of output capacitor. Turn off slew rate is not a

specified characteristic of the MIC68400.

4.7 Sequencing Configurations

Sequencing refers to timing-based Master/Slave

control between regulators. It allows a Master device to

control the start and stop timing of a single or multiple

Slave devices. In typical sequencing the Master POR

drives the Slave EN. The sequence begins with the

Master EN driven high. The Master output ramps up

and triggers the Master DLY when the Master output

reaches 90%. The Master DLY then determines when

the POR is released to enable the Slave device. When

the Master EN is driven low, the Master POR is

immediately pulled low causing the Slave to ramp

down. However, the Master output will not ramp down

until the Master DLY has fully discharged. In this way,

the Master power can remain good after the Slave has

been ramped down.

In sequencing configurations the Master DLY controls

the turn-on time of the Slave and the Slave DLY

controls the turn-off time of the Slave.

FIGURE 4-4: Sequencing Connections.

In the figure below, CDLYS > CDLYM. CDLYS = 2 nF,

CDLYM = 1 nF.

FIGURE 4-5: Delayed Sequencing.

In the figure below, CDLYS < CDLYM. CDLYS = 1 nF,

CDLYM = 2 nF.

FIGURE 4-6: Windowed Sequencing.

4.8 Tracking Configurations

4.8.1 NORMAL TRACKING

In normal tracking, the Slave RC pin is driven from the

Master output. The internal control buffering ensures

that the output of the Slave is always slightly above the

Master to guarantee that the Slave properly regulates

tRC VOUT CRC

1A

----------





=SRON 1A

CRC

----------





tRC 0.5VCRC

1A

----------





=SRON 2VOUT 1A

CRC

----------





4.7μF

DLY2

= 3.3V

IN1

OUT1

SNS1

RC1 POR1

EN1 DLY1

N

MIC68400

IN2

OUT2

SNS2

RC2 POR2

EN2

GND

DLY2

4.7μF

0.1μF

DLY1

N

μProcessor

I/O

CORE

/RESET

MIC68400

DS20005824A-page 14  2017 Microchip Technology Inc.

(based on its own internal reference) if Master and

Slave are both fixed voltage devices of the same output

voltage. The schematic and plot below show a 1.2V

device tracking a 1.8V device through the entire

turn-on/turn-off sequence. Note that because the RC

pin will overdrive the target voltage (to ensure proper

regulation), the ramp down delay is longer than the

POR delay during turn-on.

FIGURE 4-7: Fixed Voltage Devices.

Fixed voltage versions of MIC68400 have two internal

voltage dividers: one for setting the output voltage and

the other for driving the tracking circuitry. Adjustable

parts have up to two external dividers: one from output

to SNS (to set the output voltage) and one from the

output to the Slave RC pin (in tracking configurations).

Also, the RC pin in fixed parts operates at the same

voltage as the output, whereas the RC pin in adjustable

parts operates at the 0.5V reference. To set up a

normal tracking configuration, the divider driving the

Slave RC pin is the same ratio (or nearly the same – if

both Master and Slave are set to the same output

voltage, the Slave RC divider should be adjusted 2% to

4% higher) as the divider driving the Slave SNS pin.

This is shown in Figure 4-8.

FIGURE 4-8: Adjustable Voltage Devices.

10μF

= 2.5V

IN OUT

EN SNS

DLY POR

VOUT1

VOUT2

POR

N

1nF

MIC68400-1.2YML

Slave

MIC68400-1.8YML

Master

IN OUT

EN SNS

DLY

GND

PORNC

0.1μF

10μF

= 3.3V

IN OUT

DLY POR

VOUT1

VOUT2

POR

N

1nF

2nF

MIC68400YML

Master

MIC68400YML

Slave

IN OUT

DLY

GND

PORNC

0.1μF

N

N

N



N

N

ADJ

 2017 Microchip Technology Inc. DS20005824A-page 15

MIC68400

4.8.2 RATIOMETRIC TRACKING

Ratiometric tracking allows independent ramping

speeds for both regulators so that the regulation

voltage is reached at the same time. This is

accomplished by adding a resistor divider between the

Master output pin and the Slave RC pin. The divider

should be scaled such that the Slave RC pin reaches

or exceeds the target output voltage of the Slave as the

Master reaches its target voltage.

FIGURE 4-9: Fixed Voltage Devices.

Ratiometric tracking may be used with adjustable parts

by simply connecting the RC pins of the Master and

Slave. Use a single RC capacitor of twice the normal

value (because twice the current is injected into the

single RC cap). Alternatively, fixed parts may use

ratiometric tracking in a manner similar to adjustable

normal tracking, with the tracking divider changed to

the same resistor ratio driving the Master ADJ/SNS pin.

FIGURE 4-10: Adjustable Voltage Devices.

4.9 Final Note on Tracking

The MIC68400 does not fully shut down until the output

load is discharged to near zero. If RC is driven from an

external source in a tracking configuration, and the

external source does not go to zero on shutdown, it

may prevent complete shutdown of the MIC68400. This

will cause no damage, but some Q current will remain

and may cause concern in battery operated portable

equipment. Also, when RC is driven in tracking mode,

pulling EN low will not cause the output to drop.

Maintaining low EN in tracking mode simply means that

the MIC68400 will shutdown when the tracking voltage

gets near zero. In no case can the MIC68400 enter the

tracking mode unless EN is pulled high.

10μF

= 3.3V

IN OUT

EN SNS

DLY POR

VOUT1

VOUT2

POR

N

1nF

MIC68400-1.2YML

Slave

MIC68400-1.8YML

Master

IN OUT

EN SNS

DLY GND

GND

PORNC

N

N

0.1μF

10μF

= 3.3V

IN OUT

DLY POR

VOUT1

VOUT2

POR

N

1nF

3nF

MIC68400YML

Slave

Master

MIC68400YML

IN OUT

DLY GND

GND

PORNC

0.1μF

N

N

N

N

ADJ

MIC68400

DS20005824A-page 16  2017 Microchip Technology Inc.

5.0 PACKAGING INFORMATION

5.1 Package Marking Information

Example

X.XXXX

XXXXX-

16-Lead QFN*

(Fixed)

Example

16-Lead QFN*

(Adjustable)

WNNN

1.2YML

68400-

6026

XXX

XXXXX

WNNN

YML

68400

2943

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. DS20005824A-page 17

MIC68400

16-Lead 4 mm x 4 mm QFN 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.

MIC68400

DS20005824A-page 18  2017 Microchip Technology Inc.

NOTES:

 2017 Microchip Technology Inc. DS20005824A-page 19

MIC68400

APPENDIX A: REVISION HISTORY

Revision A (August 2017)

• Converted Micrel document MIC68400 to Micro-

chip data sheet DS20005824A.

• Minor text changes throughout.

• Paragraph added after Figure 4-2 in Section 4.2

“Input Capacitor”.

MIC68400

DS20005824A-page 20  2017 Microchip Technology Inc.

 2017 Microchip Technology Inc. DS20005824A-page 21

MIC68400

PRODUCT IDENTIFICATION SYSTEM

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

Examples:

a) MIC68400-1.2YML-TR: 4A Sequencing LDO with

Tracking and Ramp Control,

1.2V, –40°C to +125°C,

16-Lead QFN, 5,000/Reel

b) MIC68400-1.8YML-TR: 4A Sequencing LDO with,

Tracking and Ramp Control

1.8V, –40°C to +125°C,

16-Lead QFN, 5,000/Reel

c) MIC68400YML-TR: 4A Sequencing LDO with,

Tracking and Ramp Control

Adjustable Voltage,

–40°C to +125°C, 16-Lead

QFN, 5,000/Reel

PART NO. XX

Package

Device

Device: MIC68400: 4A Sequencing LDO with Tracking and

Ramp Control

Voltage: 1.2 = 1.2V

1.8 = 1.8V

blank= Adjustable

Temperature: Y = –40°C to +125°C

Package: ML = 16-Lead 4 mm x 4 mm QFN

Media Type: TR = 5,000/Reel

–X.

Voltage

Temperature

Note 1: Tape and Reel identifier only appears in the

catalog part number description. This identifier is

used for ordering purposes and is not printed on

the device package. Check with your Microchip

Sales Office for package availability with the

Tape and Reel option.

–XX

Media Type

MIC68400

DS20005824A-page 22  2017 Microchip Technology Inc.

NOTES:

 2017 Microchip Technology Inc. DS20005824A-page 23

Information contained in this publication regarding device

applications and the like is provided only for your convenience

and may be superseded by updates. It is your responsibility to

ensure that your application meets with your specifications.

MICROCHIP MAKES NO REPRESENTATIONS OR

WARRANTIES OF ANY KIND WHETHER EXPRESS OR

IMPLIED, WRITTEN OR ORAL, STATUTORY OR

OTHERWISE, RELATED TO THE INFORMATION,

INCLUDING BUT NOT LIMITED TO ITS CONDITION,

QUALITY, PERFORMANCE, MERCHANTABILITY OR

FITNESS FOR PURPOSE. Microchip disclaims all liability

arising from this information and its use. Use of Microchip

devices in life support and/or safety applications is entirely at

the buyer’s risk, and the buyer agrees to defend, indemnify and

hold harmless Microchip from any and all damages, claims,

suits, or expenses resulting from such use. No licenses are

conveyed, implicitly or otherwise, under any Microchip

intellectual property rights unless otherwise stated.

Trademarks

The Microchip name and logo, the Microchip logo, AnyRate, AVR,

AVR logo, AVR Freaks, BeaconThings, BitCloud, CryptoMemory,

CryptoRF, dsPIC, FlashFlex, flexPWR, Heldo, JukeBlox, KEELOQ,

KEELOQ logo, Kleer, LANCheck, LINK MD, maXStylus,

maXTouch, MediaLB, megaAVR, MOST, MOST logo, MPLAB,

OptoLyzer, PIC, picoPower, PICSTART, PIC32 logo, Prochip

Designer, QTouch, RightTouch, SAM-BA, SpyNIC, SST, SST

Logo, SuperFlash, tinyAVR, UNI/O, and XMEGA are registered

trademarks of Microchip Technology Incorporated in the U.S.A.

and other countries.

ClockWorks, The Embedded Control Solutions Company,

EtherSynch, Hyper Speed Control, HyperLight Load, IntelliMOS,

mTouch, Precision Edge, and Quiet-Wire are registered

trademarks of Microchip Technology Incorporated in the U.S.A.

Adjacent Key Suppression, AKS, Analog-for-the-Digital Age, Any

Capacitor, AnyIn, AnyOut, BodyCom, chipKIT, chipKIT logo,

CodeGuard, CryptoAuthentication, CryptoCompanion,

CryptoController, dsPICDEM, dsPICDEM.net, Dynamic Average

Matching, DAM, ECAN, EtherGREEN, In-Circuit Serial

Programming, ICSP, Inter-Chip Connectivity, JitterBlocker,

KleerNet, KleerNet logo, Mindi, MiWi, motorBench, MPASM, MPF,

MPLAB Certified logo, MPLIB, MPLINK, MultiTRAK, NetDetach,

Omniscient Code Generation, PICDEM, PICDEM.net, PICkit,

PICtail, PureSilicon, QMatrix, RightTouch logo, REAL ICE, Ripple

Blocker, SAM-ICE, Serial Quad I/O, SMART-I.S., SQI,

SuperSwitcher, SuperSwitcher II, Total Endurance, TSHARC,

USBCheck, VariSense, ViewSpan, WiperLock, Wireless DNA, and

ZENA are trademarks of Microchip Technology Incorporated in the

U.S.A. and other countries.

SQTP is a service mark of Microchip Technology Incorporated in

the U.S.A.

Silicon Storage Technology is a registered trademark of Microchip

Technology Inc. in other countries.

GestIC is a registered trademark of Microchip Technology

Germany II GmbH & Co. KG, a subsidiary of Microchip Technology

Inc., in other countries.

All other trademarks mentioned herein are property of their

respective companies.

ISBN: 978-1-5224-2075-0

Note the following details of the code protection feature on Microchip devices:

• Microchip products meet the specification contained in their particular Microchip Data Sheet.

• Microchip believes that its family of products is one of the most secure families of its kind on the market today, when used in the

intended manner and under normal conditions.

• There are dishonest and possibly illegal methods used to breach the code protection feature. All of these methods, to our

knowledge, require using the Microchip products in a manner outside the operating specifications contained in Microchip’s Data

Sheets. Most likely, the person doing so is engaged in theft of intellectual property.

• Microchip is willing to work with the customer who is concerned about the integrity of their code.

• Neither Microchip nor any other semiconductor manufacturer can guarantee the security of their code. Code protection does not

mean that we are guaranteeing the product as “unbreakable.”

Code protection is constantly evolving. We at Microchip are committed to continuously improving the code protection features of our

products. Attempts to break Microchip’s code protection feature may be a violation of the Digital Millennium Copyright Act. If such acts

allow unauthorized access to your software or other copyrighted work, you may have a right to sue for relief under that Act.

Microchip received ISO/TS-16949:2009 certification for its worldwide

headquarters, design and wafer fabrication facilities in Chandler an d

Tempe, Arizona; Gresham, Oregon and design centers in California

and India. The Company’ s quality system processes and procedures

are for its PIC® MCUs and dsPIC® DSCs, KEELOQ® code hopping

devices, Serial EEPROMs, micro perip hera ls, n onvolat ile memory and

analog products . In add ition, Microchip’s quality system for the design

and manufacture of development systems is ISO 9001:2000 certified.

QUALITYMANAGEMENTS

YSTEM

CERTIFIEDBYDNV

== ISO/TS16949==

DS20005824A-page 24  2017 Microchip Technology Inc.

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11/07/16