TK65429MTL/429_技术文档

ADVANCED INFORMATION

TK654xx

ADVANCED

INFORMATION

STEP-DOWN CONVERTER WITH BATTERY MONITOR

FEATURES

APPLICATIONS

■ Minimum External Component Count (1 coil, 1 cap)

■ Miniature 6 Pin SOT23L-6 Surface Mount Package

■ Up To 95% Efficient

■ Battery Powered Systems

■ Cellular Telephones

■ Pagers

■ Personal Communications Equipment

■ Radio Controlled Systems

■ Toys

■ Extremely Low Operating Current (24 µA)

■ Low Quiescent Current (18 µA)

■ Low Ripple

■ Fast Transient Response

Driving the SB pin low will disable the TK654xx and drop

the quiescent current on the input supply to approximately

18 µA.

■ Linear Dropout Characteristics

■ Short Circuit Protection

■ Regulates Down to 1.8 V

Pulse Current Amplitude control is used to regulate the

voltage at the V_OUTpin of the IC. When the output voltage

of the TK654xx drops below the regulation threshold, a

current pulse is transferred from the input supply to the

output. TheTK654xxutilizesaproprietarycontrolscheme,

where the average amplitude of the current pulse is varied

depending upon the current loads. The proprietary

architecture allows fast transient response and minimal

ripple while maintaining ease-of-use and low component

count.

■ Synchronous Rectification

■ Internal Battery Monitor

DESCRIPTION

The TK654xx low power step-down converter is designed

for portable battery systems, capable of operating from a

singleLi-ionbatterycell ormultiplealkalineorrechargeable

(NiCd or NiMH) battery cells (up to 6 V). The TK654xx

provides the power switch, synchronous rectifier, and the

control circuit for a buck step-down converter. Only two

external components are required to complete the step-

down conversion.

The TK654xx is available in a miniature 6-pin SOT23L-6

surface mount package.

TK654xxM

The TK654xx provides laser-trimmed output voltages

ranging from 1.8 V to 3.3 V. The low resistance MOSFET

switch and synchronous rectifier allow average currents

up to 200 mA, while maintaining peak efficiencies up to

95%. A low-battery threshold and turn-off threshold can

be individually programmed by the user, utilizing a single

resistor divider connected to the Low Battery Input (LBI)

pin. When the resistively-divided supply voltage on the

LBIpindropsbelowapproximately1.22V, theLowBattery

Output (LBO) pin will become asserted. The dual-function

LBI pin can alternatively be used as a Standby (SB) pin.

LBO

LBI/SB

GND

V

OUT

SW

V

IN

BLOCK DIAGRAM

V

IN

ORDERING INFORMATION

TK654xxM

CONTROL

CIRCUIT

V

SW

OUT

GND

Tape/Reel Code

REF

OFF

LBO

Voltage Code

BATTERY

MONITOR

LBO

LBI/SB

VOLTAGE CODE

TAPE/REEL CODE

27 = 2.7 V

18 = 1.8 V

21 = 2.1 V

24 = 2.4 V

25 = 2.5 V

TL: Tape Left

30 = 3.0 V

33 = 3.3 V

September 1999 TOKO, Inc.

Page 1

ADVANCED INFORMATION

TK654xx

ABSOLUTE MAXIMUM RATINGS

All Pins Except GND ............................................... 6.5 V

Power Dissipation (Note 1) ................................ 400 mW

Storage Temperature Range ................... -55 to +150 °C

Operating Temperature Range ...................-20 to +80 °C

Junction Temperature ........................................... 150 °C

Lead Soldering Temperature (10 s.) ..................... 235 °C

TK654xx ELECTRICAL CHARACTERISTICS

Test conditions: V_IN= 5 V, I_OUT= 1 mA, T_A= T_J= Full Operating Temperature Range, unless otherwise specified.

SYMBOL

V_IN

PARAMETER

Input Voltage

TEST CONDITIONS

MIN

2

TYP

MAX

6

UNITS

V

T_A= T_J= 25 ° C (Note 2)

-3%

-5%

V_REG

3%

+5%

120

20

V

V_OUT(REG)

Output Voltage

V

∆V_OUT(LOAD)

∆V_OUT(LINE)

Load Regulation

Line Regulation

I_LOAD= 0 to 100 mA, (Note 3)

V_IN= 4 to 6 V, (Note 3)

45

6

mV

V_OUT= V_OUT(REG)+ 50 mV

(Note 3)

I_Q(VOUT)

Quiescent Current into V_OUTPin

10

50

µA

P

I_Q(VIN)

Quiescent Current into V_INPin

LBI Input Threshold

V_OUT= V_OUT(REG)+ 50 mV

T_A= T_J= 25 ° C

Note 3

15

1.22

0

65

µA

V

V_TH(LBI)

V_TH(SB)

1.157

1.282

Standby Threshold

V

nA

mA

µA

I_B(SB)

SB Input Bias Current

Note 4 at (V_TH(SB)- 100 mV)

(Note 3)

400

720

100

1000

I_OUT(MAX)

I_OUT(SC)

I_Q(CONV)

I_STBY

Maximum Output Current

Short Circuit Current

(Note 3)

250

90

Converter Quiescent Current

Converter Standby Current

(Note 3) I_OUT= 0 mA

SB pin = 0 V, Pin 1 open

24

18

65

I_OUT= 50 mA, (Note 3)

T_A= T_J= 25° C (TK65418)

86

90

91

95

%

EFF

Converter Efficiency

Dropout Voltage

I_OUT= 50 mA, (Note 3)

T_A= T_J= 25° C (TK65433)

I_OUT= 50 mA, (Note 5)

T_A= T_J= 25 ° C (TK65418)

100

75

195

145

mV

V_DROP

I_OUT= 50 mA, (Note 6)

T_A= T_J= 25 ° C (TK65433)

Note 1: Power dissipation is 400 mW when mounted as recommended. Derate at 3.2 mW/°C for operation above 25 °C. Power dissipation is 200

mW in Free Air. Derate at 1.6 mW/°C for operation above 25 °C

Note 2: V_REG= 3.3, 3.0, 2.7, 2.5, 2.4, 2.1, 1.8 V.

Note 3: When using test circuit.

Note 4: When using test circuit and ramping V down.

IN

Note 5: When using test circuit with SB pin resistors removed and tied to V . (V = 1.8 V)

IN

Note 6: When using test circuit with SB pin resistors removed and tied to V . (V = 3.3 V)

IN

Page 2

September 1999 TOKO, Inc.

ADVANCED INFORMATION

TEST CIRCUIT

TK654xx

I

Q(CONV)

V

= 5 V

IN

C

R

1

634 K

3

R

3

10 µF

300 K

LBO

OUT

SW

LBI/SB

GND

I

Q(VOUT)

R

2

287 K

V

I

OUT

V

IN

V

OUT

L

1

I

+

100 µH

Q(VIN)

C

1

C

2

10 µF

L₁: Toko DL10: F Coil, PN A814AY-101K

C₁,C₃: Ceramic 10 µF

C₂: Tantalum 10 µF

TYPICAL PERFORMANCE CHARACTERISTICS

USING TEST CIRCUIT

TK65433

LINE REGULATION

TK65418

LINE REGULATION

3.330

3.325

3.320

3.315

3.310

3.305

3.300

1.820

1.815

I

= 1 mA

I

= 1 mA

OUT

1.810

1.805

1.800

1.795

1.790

3.4 3.8 4.2 4.6 5.0 5.4 5.8 6.0

2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0

V

(V)

V

(V)

IN

TK65418

LOAD REGULATION

TK65433

LOAD REGULATION

3.35

3.3

1.82

1.80

1.78

1.76

V

= 5 V

V

= 5 V

IN

3.25

3.2

0

20

40

I

60

80 100 120

0

20 40 60 80 100 120 140 160

(mA)

I

OUT

September 1999 TOKO, Inc.

Page 3

ADVANCED INFORMATION

TK654xx

TYPICAL PERFORMANCE CHARACTERISTICS

USING TEST CIRCUIT (CONT.)

TK65418

LOAD AND TEMPERATURE

REGULATION

TK65433

LOAD AND TEMPERATURE

REGULATION

1.90

1.88

1.86

1.84

1.82

1.8

3.55

3.45

I

= 50 mA

OUT

3.35

3.25

I

= 1 mA

OUT

I

= 1 mA

I

= 100 mA

OUT

I

= 50 mA

1.78

1.76

1.74

1.72

OUT

I

= 100 mA

3.15

3.05

OUT

-50 -25

0

25 50 75 100 125

-50 -25

0

25 50 75 100 125

TEMPERATURE (°C)

TK65418

EFFICIENCY vs.

OUTPUT CURRENT

TK65433

EFFICIENCY vs.

OUTPUT CURRENT

100

90

80

70

60

90

80

70

60

50

40

30

20

10

0

50

40

30

20

10

0

20

40

I

60

80 100 120

0

40

80

(mA)

120

160

(mA)

I

OUT

TK65418

EFFICIENCY vs. TEMPERATURE

TK65433

EFFICIENCY vs. TEMPERATURE

100

95

90

85

80

75

99

97

95

93

91

89

87

85

I

= 50 mA

OUT

I

= 50 mA

OUT

-50 -25

0

25 50 75 100 125

-50 -25

0

25 50 75 100 125

TEMPERATURE (°C)

Page 4

September 1999 TOKO, Inc.

ADVANCED INFORMATION

TK654xx

TYPICAL PERFORMANCE CHARACTERISTICS

USING TEST CIRCUIT (CONT.)

TK65418

TK65433

CONVERTER QUIESCENT

CURRENT vs.

CONVERTER QUIESCENT

CURRENT vs.

INPUT SUPPLY VOLTAGE

26

25.5

25

26

25.5

25

No Load

24.5

24

24.5

24

23.5

23

23.5

23

22.5

22

22.5

22

2

3

4

5

6

3.5

4

4.5

V

5

5.5

6

V

(V)

IN

TK65418

TK65433

CONVERTER QUIESCENT

CURRENT vs.

CONVERTER QUIESCENT

CURRENT vs.

TEMPERATURE

200

150

200

150

100

50

No Load

100

50

0

-50 -25

0

25 50 75 100 125

-50 -25

0

25 50 75 100 125

TEMPERATURE (°C)

TK65418

STANDBY CURRENT vs.

INPUT SUPPLY VOLTAGE

TK65433

STANDBY CURRENT vs.

INPUT SUPPLY VOLTAGE

25

20

15

10

5

25

20

15

10

5

2

2.5

3

3.5

4

4.5

(V)

5

5.5

6

2

2.5

3

3.5

4

4.5

(V)

5

5.5

6

V

IN

September 1999 TOKO, Inc.

Page 5

ADVANCED INFORMATION

TK654xx

TYPICAL PERFORMANCE CHARACTERISTICS (CONT.)

TK65433

STANDBY CURRENT vs.

TEMPERATURE

TK65418

STANDBY CURRENT vs.

TEMPERATURE

80

60

40

20

0

80

60

40

20

0

-50 -25

0

25 50 75 100 125

-50 -25

0

25 50 75 100 125

TEMPERATURE (°C)

TK65418

MAX OUTPUT CURRENT vs.

INDUCTOR VALUE

TK65433

MAX OUTPUT CURRENT vs.

INDUCTOR VALUE

350

300

250

200

150

100

50

350

300

250

200

150

100

50

0

60

90

120

150

180

90

120

150

180

INDUCTOR VALUE (µH)

Page 6

September 1999 TOKO, Inc.

ADVANCED INFORMATION

TK654xx

TYPICAL PERFORMANCE CHARACTERISTICS (CONT.)

USING RIPPLE TEST CIRCUIT

V

= 5 V

IN

C

3

10 µF

LBO

LBI/SB

GND

OPEN

V

OUT

SW

L

1

V

IN

V

OUT

100 µH

+

C

1

2

L₁: Toko D10F Coil, PN A814AY-101K

C₁= See Figure Below

C₂= Tantalum 10 µF

C₃= Ceramic 10 µF

PEAK TO PEAK RIPPLE VOLTAGE

RIPPLE vs. OUTPUT CURRENT

70

C

= 10 µF Tantalum

2

60

50

40

30

20

10

0

C

= 10 µF

1

C

= 20 µF

1

C

= 50 µF

= 80 µF

80

1

C

1

0

20

40

60

100

I

(mA)

OUT

September 1999 TOKO, Inc.

Page 7

ADVANCED INFORMATION

TK654xx

TYPICAL PERFORMANCE CHARACTERISTICS (CONT.)

STARTUP TRANSIENT WAVEFORMS

TK65433 - Power Up No Load

TK65418 - Power Up No Load

1.8V

0.0V

3.3V

0.0V

Output Voltage (2V / div)

Output Voltage (1V / div)

200mA

0mA

200mA

0mA

Inductor Current (100mA / div)

TK65418 - Power Up 100mA Load

TK65433 - Power Up 100mA Load

1.8V

3.3V

0.0V

Output Voltage (1V / div)

Output Voltage (2V / div)

0.0V

Inductor Current (100mA / div)

200mA

0mA

Inductor Current (100mA / div)

TK65418 - Power Up using SB Pin (100mA Load)

TK65433 - Power Up using SB Pin (100mA Load)

1.8V

3.3V

0.0V

Output Voltage (1V / div)

Output Voltage (2V / div)

0.0V

Inductor Current (100mA / div)

200mA

0mA

Page 8

September 1999 TOKO, Inc.

ADVANCED INFORMATION

TK654xx

TYPICAL PERFORMANCE CHARACTERISTICS (CONT.)

TURN OFF TRANSIENT WAVEFORMS

TK65418 - Power Down using SB Pin (100mA Load)

TK65433 - Power Down using SB Pin (100mA Load)

1.8V

0.0V

3.3V

0.0V

Output Voltage (1V / div)

Output Voltage (2V / div)

200mA

0mA

200mA

Inductor Current (100mA / div)

0mA

LOAD TRANSIENT RESPONSE WAVEFORMS

TK65433 - Transient Load (0mA to 100mA Step)

TK65418 - Transient Load (0mA to 100mA Step)

Output Voltage (50mV / div)

Inductor Current (100mA / div)

200mA

0mA

200mA

0mA

TK65418 - Transient Load (100mA to 0mA Step)

TK65433 - Transient Load (100mA to 0mA Step)

Output Voltage (50mV / div)

200mA

0mA

200mA

0mA

Inductor Current (100mA / div)

September 1999 TOKO, Inc.

Page 9

ADVANCED INFORMATION

TK654xx

THEORY OF OPERATION

SW1

L

Figure 1 illustrates a circuit diagram for a simple buck

V

OUT

(step-down) converter. Typically, the input voltage (V ) is

IN

+

greater than the output voltage (V

). By modulating the

OUT

D

C

V

IN

switching action of switch SW1, the output voltage (V

)

OUT

can be regulated to a constant voltage that is relatively

independent of variations in the input supply (V ) or the

IN

current load on the V

node. The TK654xx contains all

OUT

FIGURE 1: SIMPLE "BUCK" CONVERTER

the control circuitry, logic, and power switch (SW1) for

implementing a simple step-down or "buck" converter, as

shown in Figure 1.

The control scheme for the TK654xx forces the converter

tostepthroughthe"on,""off,"and"null"statesinsequence.

Assume that the controller is initially in the "null" state and

In general, a switching converter utilizing the TK654xx

controller will be operating in one of three states:

V

is greater than the regulation threshold. As soon as

OUT

theoutputvoltagedropsbelowthisthreshold,thecontroller

willswitchfrom"null"statetothe"on"state. Duringthe"on"

state, current through inductor (L) will be increasing.

Current will flow from the input supply to the output

capacitor through the inductive element. In this state,

energy is transferred directly from the input supply to the

output through the inductor. The maximum duration of the

"on"stateisinverselyproportionaltothedifferencebetween

1. "ON" STATE: During this state of operation SW1 will be

turnedon. Currentthroughtheinductiveelement(L)willbe

increasing at a rate proportional to the voltage difference

between V and V

. In this state, there is a direct

IN

OUT

current path from the input supply to the output load

through the inductor L.

2. "OFF" STATE: During this state of operation SW1 will

be turned off. Current through the inductive element will be

greater than zero and flowing either through the external

schottkyrectifier(D)orthesynchronousrectifierinternalto

the TK654xx. During the "off" state, current through the

inductive element (L) will be decreasing at a rate

the input voltage (V ) and the output voltage (V

).

IN

OUT

The transition from the "on" state to the "off" state can be

initiated by one of two different means. As mentioned

above, the maximum duration of the "on" state is inversely

proportional to the difference between the input voltage

approximately proportional to V

. In this state, the

(V ) and the output voltage (V

). If the duration of the

OUT

IN

OUT

current drawn from the input supply is essentially zero.

Current to the load is provided by stored energy in the

inductive element.

"on" cycle exceeds this maximum, the controller

immediately switches to the "off" state independent of

other factors. Understanding that when the converter is in

a dropout condition (V ≈ V

), the maximum “on” time

IN

OUT

3. "NULL" STATE: During this state of operation SW1 will

be turned off. Current through the inductive element will be

approximately zero. The internal synchronous rectifier will

be turned off. All current demands of the load will be

provided by the output filter capacitor (C). In this state, the

current drawn from the input supply is essentially zero.

Since the inductive current is zero, no additional energy is

available from the inductor. If the current demands of the

load are very light, the current will be provided by the

stored charge in the output filter capacitor. If the voltage of

thefiltercapacitordropsbelowtheregulationthreshold, an

"on" state will be initiated and additional energy will be

transferred from the input supply to the output.

is infinite and the “on” state is constantly applied. By

limiting the duration of the "on" cycle, the peak inductor

current is also being limited. The second method for

initiatingthe"off"cycleistriggeredwhenthedurationofthe

"on" cycle exceeds a minimum on-time duration and the

output voltage (V

) exceeds the regulation threshold.

OUT

Therefore, the actual duration of the "on" cycle will vary

between a minimum on-time (T ) and a maximum

ON(MIN)

on-time (T

) depending upon the load current. At

ON(MAX)

very light loads the on-time duration will be at a minimum;

at very heavy loads the on-time will be at a maximum. This

ability to vary the duration of the on cycle is a proprietary

control scheme which can produce a ten-fold reduction in

ripple when compared to competing devices.

The transition from the "off" state to the "null" state occurs

after sufficient time has been allowed for the inductor

current to return to zero. The actual duration of the "off"

Page 10

September 1999 TOKO, Inc.

ADVANCED INFORMATION

TK654xx

THEORY OF OPERATION (CONT.)

cycle will be dependent upon the duration of the preceding

"on" cycle and the sensed input and the output voltages.

As the battery voltage drops, the voltage on the V_LBIpin will

dropproportionately. WhenthevoltageontheLBIinputpin

passes through approximately 1.22 V, the output of the

first comparator (LBO) will transition from a high to a low

state and the synchronous rectifier N-channel MOSFET

willstopbeingswitched.Thereisabout50mVofhysteresis

betweentheLBOtrippointanditsresetpoint. Shortlyafter

the LBO output has been asserted, as the input voltage

continues to drop, the magnitude of the current out of the

V_LBIpin will begin to flow and proportionately increase as

the input voltage decreases. An op-amp feedback loop

internal to the Battery Monitor of the TK654xx will attempt

to maintain the voltage on the V_LBIpin at a constant value

of approximately 1.22 V (thus, the plateau). As the battery

voltage continues to drop, there comes a point where the

feedback current stops increasing at about 720 nA. At this

point, the voltage on the LBI pin will resume a proportional

drop with the input voltage and the TK654xx converter will

turn off.

Theapproximatedurationofthe"off"cyclecanbepredicted

as follows:

T

= T

X (V - V

) / V

OUT OUT

OFF

ON

IN

During the majority of the "off" cycle, a power switch is

turned on. The turn-on point of the switch is synchronized

withtheinitiationofthe"off"cycle. Theturn-offpointisnear

the end of the "off" cycle. The addition of this switch

reduces the voltage drop across the external rectifying

deviceandprovidessignificantimprovementsinconverter

efficiency.

BATTERY MONITOR SECTION

Inatypicalvoltagemonitor,whichusesanexternalresistive

divider for setting the voltage monitor threshold, the input

bias current to the monitor pin is essentially zero. In this

type of scenario, the voltage on the monitor input would be

a resistively divided version of the battery voltage. The

BatteryMonitoroftheTK654xxintroducesasmallfeedback

current (-I_LBI) which introduces a “plateau” into the transfer

characteristicsbetweenthebatteryvoltageandthevoltage

monitoring pin. The width of this plateau is dependent

upon the current range of the feedback current (-I_LBI) and

the values of the external resistor network. Figure 2

illustrates the typical relationship between the battery

voltage (V_IN), the feedback current (-I_LBI) and the voltage

on the monitoring pin (V_LBI).

For details on how to properly select the resistor divider,

refer to the “Design Considerations” section.

V

LBO

V

IN

V

OFF

1.22 V

V

LBI

720 nA

0 nA

-I

LBI

In selecting a resistor divider network, there are typically

two degrees of freedom when selecting values. The first

criteria in selecting the divider is the ratio of the two

resistors. Selecting the ratio defines the upper threshold of

the voltage monitor. The second degree of freedom when

selecting the resistor divider is the absolute resistance

values. This second degree of freedom can be utilized to

set a secondary monitoring threshold (V_OFF) lesser than

the first.

LBO

OFF

FIGURE 2: BATTERY MONITOR OPERATION

GRAPHS

Typically, when the battery voltage is relatively high, the

voltage on the LBI input pin will be a resistively divided

version of the battery voltage.

September 1999 TOKO, Inc.

Page 11

ADVANCED INFORMATION

PIN DESCRIPTION

TK654xx

INPUT VOLTAGE PIN (V )

IN

The second function of this pin is to act as a Standby (SB)

input. If this pin is greater than approximately 1.22 V, the

converter will operate normally. Driving this pin low will force

the converter into a "standby" mode where the DC/DC

conversion is disabled. In this "standby" mode, the current

through the inductive element goes to zero; only the filter

capacitor will provide current to the output.

This pin is the positive input supply for the TK654xx. Current

flowing into this pin provides power to the IC and to the

converter output through the inductive element. During the

"on" state, the majority of the current flowing into this pin is

flowingthroughtheinductor.Duringthe"off"and"null"states,

the current into this pin is very small (approximately 18 µA).

The voltage source driving this pin should have relatively low

AC impedance. Good design practices dictate decoupling to

the GND pin.

If neither the Low-Battery or Standby features are needed,

this input pin should be connected directly to the V pin.

IN

Underthismodeofoperation,theTK654xxwillnotturnoff. As

the input voltage approaches the regulation voltages the

TK654xx will act as a P-Channel pass element with

approximately a 2 Ω resistance, going into the linear mode of

operation.

GROUND PIN (GND)

This pin provides the ground connection for the IC.

OUTPUT VOLTAGE PIN (V

)

OUT

LOW BATTERY OUTPUT PIN (LBO)

This pin senses the output voltage of the buck converter.

Input current into this pin is very low (approximately 10 µA).

TheoutputvoltageisresistivelydividedintheICandcompared

to the bandgap voltage. If the output voltage remains greater

than the regulation threshold, the TK654xx remains in a

standby state. As soon as the output voltage drops below the

regulationthreshold,theTK654xxwillinitiatean"on"and"off"

cycle to boost the output voltage.

This pin provides a Low Battery Output (LBO) signal to

indicate when the voltage on the LBI input pin has dropped

below the low battery threshold (1.22 V). This open-drain

output is normally pulled up to either the input supply or the

output supply through a resistive pull-up. The LBO output pin

provides an active-low output. If the LBO is not going to be

used, the pin may be left open.

SW PIN

This pin is normally connected to one pin of the inductive

element and an external optional passive schottky rectifier

(optionaltoincreaseefficiency).Theexternalschottkyrectifier

isconnectedbetweenthispinandground.Itisrecommended

that the lead lengths between the rectifier and the pins of the

TK654xx be kept as short as possible to minimize parasitic

inductances.

LOW BATTERY INPUT/STANDBY PIN (LBI/SB)

Thisinputpiniscapableofperformingtwoseparatefunctions

whichwillbedependentupontheapplication'srequirements.

In some applications, this input pin can be used as a Low

Battery Input (LBI). In such an application, this input pin is

typically driven by a resistively divided version of the input

supply (V ). For detailed information on selecting values for

IN

the resistor divider, please refer to Design Considerations on

pages 13 and 14.

Page 12

September 1999 TOKO, Inc.

ADVANCED INFORMATION

DESIGN CONSIDERATIONS

TK654xx

INDUCTOR SELECTION

shutdown threshold which occurs at a voltage lower than

theLBIthreshold.BoththeLBIthresholdandtheshutdown

threshold can be set utilizing a single resistive divider.

One of the positive features of the TK654xx is the ability to

limit the magnitude of the short circuit current without the

need for external current sensing resistors. Since the

maximum on-time duration is limited, and the converter

alwaysoperatesindiscontinuousconductionmode(DCM),

the maximum load current is essentially dependent upon

the selection of the inductor value. The following table

defines the maximum load current as a function of the

inductor value.

For the following explanation, please refer to Figure 3.

When the battery voltage (V ) is very high, the current

IN

from the LBI input pin is essentially zero. The voltage on

the LBI input pin is simply a resistively-divided version of

the V pin.

IN

V

IN

300 k

R

1

2

L

MAX LOAD

305 mA

140 mA

65 mA

LBO

LBI/SB

GND

LBO

OUTPUT

47 µH

100 µH

220 µH

470 µH

V

OUT

SW

V

IN

20 mA

FIGURE 3: LOW BATTERY MONITOR

OUTPUT FILTER CAPACITOR SELECTION

As the voltage on the LBI input pin drops and passes

through the bandgap voltage (1.22 V), the LBI input pin will

begin to source current. At this same point, the LBO output

will be asserted. The assertion of the LBO output is

typically used as an early warning, indicating that battery

failure is approaching.

The purpose of the filter capacitor on the output is to

temporarily provide current to the load as inductor current

is ramping upward or downward. In general, larger

capacitors will reduce the magnitude of the ripple.

INPUT FILTER CAPACITOR SELECTION

As the voltage on the V pin continues to drop, the current

IN

sourced by the LBI input pin will continue to linearly

increase with the drop-in supply voltage. The current from

the LBI input pin will attempt to keep the voltage pin at the

same potential as the bandgap reference (1.22 V).

Throughout this region, the LBO output is continuously

asserted.

Typically, the power supply or battery source connected to

the V pin contains an inductive and resistive component.

IN

Since the current draw from the input supply varies with

time, such a scenario would exhibit ripple on the input

supply. Adding a bypass capacitor between the V pin

IN

and ground, in some cases, will dramatically decrease

rippleontheinputsupply.Aninputsupplybypasscapacitor

in the range of 1 to 10 µF will work well for most converter

applications up to 100 mA. Bypass capacitors on the input

pin should exhibit relatively good ESR characteristics.

The current sourced from the LBI input pin is internally

limited to a maximum of approximately 720 nA. As

mentioned above, the current from the LBI input pin

continues to increase as the supply voltage drops. When

the current from the LBI input pin reaches the 720 nA

threshold,theTK654xxwillturnoff.Thisessentiallyprovides

a second threshold, less than the LBI/SB threshold, where

the system will turn off.

LOW BATTERY MONITOR

TheTK654xxutilizesaproprietarymethodforsensingand

handling low battery voltages. Using a single input pin and

resistive divider, the TK654xx not only provides an early

warning system of a low battery, it also provides a later

September 1999 TOKO, Inc.

Page 13

ADVANCED INFORMATION

TK654xx

DESIGN CONSIDERATIONS (CONT.)

The thresholds for the Low Battery Input (LBI) and the turnoff (V

) can be set independently using a single resistive

OFF

divider. Equations and a chart for selecting the LBI and V

thresholds are provided below:

OFF

LBI threshold = 1.22 V X (R + R ) / R

1

2

V

threshold = LBI threshold - 720 nA X R

OFF

1

LBI THRESHOLD

4.0 V

3.5 V

V

THRESHOLD (R = 243 K)

1

OFF

(R = 487 K)

1

3.0 V

2.5 V

2.0 V

(R = 732 K)

1

(R = 976 K)

1

0.6

1.0

1.4

1.8

RATIO OF R /R

1

2

DROPOUT CHARACTERISTICS

In battery powered applications, the input supply is not typically a constant value. As the battery discharges, the input

voltage will approach the output voltage. As the voltage on the input of the converter drops, the following two

characteristics can be observed: (a) as the battery voltage drops, output ripple will increase, (b) at very low battery levels

and high current loads, the output voltage may drop significantly below the regulation threshold.

In some applications, the above characteristics may not present a problem. For those applications that may be sensitive

to these characteristics, the LBO output can provide an early warning system indicating that battery failure is near. As

the battery voltage continues to drop, the turnoff feature of the TK654xx will ultimately turn the converter off (see LBI

Indicator section).

Page 14

September 1999 TOKO, Inc.

ADVANCED INFORMATION

NOISE CONSIDERATIONS

TK654xx

GENERAL

Because of the switching waveforms inherent to the operation of DC-DC converters, they tend to be noisier than their

linear counterparts. A DC-DC converter uses switching techniques to do the power conversion at higher efficiencies than

a linear regulator at the price of noisier output ripple. The TK654xx is no exception to this, even though the proprietary

architecture chosen was centered in providing the user fast transient response, low quiescent current and minimum

ripple.

INPUT/OUTPUT CAPACITORS (GENERAL)

By the nature of their operation, DC-DC converters generate large switching currents on both the input and output of the

circuit. The input and output capacitors should be as large as practical with a low Equivalent Series Resistance (ESR).

Since low temperatures cause the value of capacitance to decrease and the ESR to increase, care should be taken to

select capacitors that have acceptable characteristics over the desired operating temperature range.

INPUT CAPACITOR

The function of the input capacitor is to reduce the supply impedance and to provide sufficient input current during

switching for stable circuit operation. The input capacitor should be physically located as close as posssible to the

converter to minimize the lead inductance and to reduce the impedance of the source at high frequencies. By having

the capacitor close to the converter, the switching current pulses are supplied locally by the capacitor instead of running

across the printed circuit board by long etch runs. This greatly reduces the noise on the board.

OUTPUT CAPACITOR

The function of the output capacitor is to reduce the ripple voltage appearing on the converter output. The output ripple

voltage is the AC voltage which appears on the regulated DC output. It is inherent in all DC-DC converters and is the

result of the conversion of the input DC to AC and then back to output DC. The output ripple is the result of two factors,

which are 90° out of phase. The first factor is the result of the change in the stored charge of the output capacitor as it

is charged by the switching current from the converter and then discharged by the load current. This factor determines

the value (µF) of the output capacitor. The second factor is the product of the capacitor’s charge/discharge current times

its ESR. This factor determines the requirement for low ESR capacitors. In DC-DC converters, the ripple produced by

the capacitor ESR is often larger than the ripple produced by the change in charge. For this reason, high quality ceramic,

tantalum, or aluminum filter capacitors are required to minimize the output ripple. This contribution to output ripple and

noise can also be minimized by the addition of a small (0.01 µF to 0.1 µF) ceramic capacitor in parallel with the bulk output

capacitor. Adding a Pi filter as shown below (Figure 4) can further reduce output noise. The Pi filter has a tendency to

reduce the efficiency by a couple of percentage points and yet the noise improves by 20 dB/decade.

LBO

OUT

SW

LBI

V

GND

V

IN

V

= 5 V

IN

V

OUT

L

1

1Ω

100 µH

D

22 µF

C

1

LL 103

22 µF

OPTIONAL

FILTER

FIGURE 4: OPTIONAL PI FILTER

September 1999 TOKO, Inc.

Page 15

ADVANCED INFORMATION

TK654xx

NOISE CONSIDERATIONS (CONT.)

COIL

The coil magnetic field can also be a source of noise. This noise is more characteristic of radiated Electromagnetic

Interference (EMI). This radiated noise can interfere with RF communications systems if care is not taken by the system

designer. A shielded coil can improve this source of EMI.

SNUBBER

When the inductor current flowing through the output diode decays to zero, the parasitic capacitance at the switch pin

(pin 3) resulting from the internal switch and external diode has energy which rings back into the inductor. This high

frequency ringing is an undesirable source of radiated noise. Fortunately, due to the low amount of energy in this ringing,

a simple RC snubber as shown in Figure 5 easily eliminates it. In low noise applications the RC snubber is recommended,

although an efficiency penalty of approzimately 2% will result.

LBO

OUT

SW

LBI

V

GND

V

IN

V = 5 V

IN

V

= 3 V

OUT

L

1

100 µH

C

D

220

PF

1

22 µF

LL 103

1 K

FIGURE 5: OPTIONAL SNUBBER

Page 16

September 1999 TOKO, Inc.

ADVANCED INFORMATION

COIL CONSIDERATIONS

TK654xx

There are several issues to consider when choosing the proper coil for the TK654xx Step-Down Converter.

An important consideration is the coil manufacturer. Toko Inc. has been in the coil business for many years and has been

a leader in this market with high quality of product, low cost, and high volume delivery distribution.

The test circuit in this data sheet uses the D10F type series for its low resistance (0.27 Ω for 100 µH). This coil should

be considered when the user is interested in high efficiency.

TYPE D10F

For Reflow Soldering

Frequency Range: 1 kHz ~ 1 MHz

Inductance Range: 10 ~ 1500 µH

Unit:mm

Amajorissuetodayisspaceaswellasheight. Tokomakesalowprofilesurfacemountcoilserieswhichmayaccomodate

this requirement. The D52 series dimensions are shown below. The 100 µH coil has a maximum rated DC resistance

of 1.6 Ω.

TYPE D52FU

Frequency Range: 1 kHz ~ 2 MHz

Inductance Range: 100 µH ~ 6800 µH

FEATURES

• Low profile (2.0 mm typ. height) and 5 mm square

• Magnetically shielded version, unshielded also available

• Available on tape and reel for auto insertion

• Suitable for reflow soldering

September 1999 TOKO, Inc.

Page 17

ADVANCED INFORMATION

COIL CONSIDERATIONS (CONT.)

TK654xx

Toko makes other series of coils which fall between the D10F and D52 series.

The D73/D75 coils should be kept in mind.

TYPE D73C, D75C

For Reflow Soldering

Frequency Range: 10 kHz ~ 1 MHz

Inductance Range: 1-560 µH

D73C

D75C

D75

Unit:mm

FEATURES

• Miniature surface mount type

• Low profile (3.0 ~ 5.1 mm max height)

• Inductance range: 1-560 µH

• Available in magnetically shielded or unshielded versions

• Supplied on tape and reel for auto insertion

• Ideal for a variety of DC-DC Converter inductor applications

D73

Unit:mm

Page 18

September 1999 TOKO, Inc.

ADVANCED INFORMATION

APPLICATION INFORMATION

TK654xx

LBO

OUT

SW

LBI

LBO

OUT

SW

SB

STANDBY

V

GND

V

GND

V

IN

V

IN

V

= 5 V

V

= 3 V

IN

V

= 5 V

IN

OUT

V

= 3 V

OUT

L

1

L

1

100 µH

C

1

C

1

22 µF

FIGURE 6: MINIMUM DEVICE COUNT

FIGURE 7: CONVERTER WITH STANDBY

V

= 5 V

IN

V

= 5 V

IN

R

1

634 K

R

1

3

R

3

634 K

300 k

LBO

OUT

SW

LBI

LBO

OUT

SW

LBI

LB OUT

R

V

2

GND

R

V

2

GND

287 K

V

IN

V

IN

V

= 3 V

OUT

V

= 3 V

OUT

L

1

L

1

100 µH

C

1

C

1

D

1

(optional)

C

2

22 µF

20 µF

10 µF

FIGURE 8: LOW BATTERY DETECTOR

FIGURE 9: EVALUATION BOARD SCHEMATIC

V_OUT

V_IN

V_OUT

GND

V_IN

GND

C1

C2

L1

*

*D Optional

1

LBO

FIGURE 9C: EVALUATION BOARD COMPONENT

PLACEMENT

FIGURE 9B: EVALUATION BOARD ARTWORK

September 1999 TOKO, Inc.

Page 19

ADVANCED INFORMATION

TK654xx

APPLICATION INFORMATION (CONT.)

The portable market, computing market and communications market, appear to not only be growing very fast, but also to

be converging.

Whether a computer incorporates communications capability or the phone incorporates the data / file transfer capability,

bothmarketsasweapproachthenextmilleniumcertainlyareportableandrequirehighefficienciesaswellaslongstandby

times in order to extend the battery life. As the user gets more and more comfortable with his portable system, he will want

longer and longer time before recharging the battery.

WIRELESS PORTABLE SYSTEM USING LINEAR REGULATORS

Power

Amp

Enable A

Enable B

Enable D

Enable E

Enable A

Enable B

Enable D

Enable E

µ Controller

FIGURE 10: Linear regulators power up wireless application

Page 20

September 1999 TOKO, Inc.

ADVANCED INFORMATION

TK654xx

APPLICATION INFORMATION (CONT.)

New microprocessors are earnestly addressing this power issue by reducing the voltage. Battery manufacturers are

wakinguprightbeforetheendofthecenturywiththeintroductionofthe“polymerelectrolytebattery”whichallowsforhigher

volumetric and gravimetric densities. Furthermore, these types of batteries come with much better form factors.

Unfortunately the wireless transmit and receive section of the portable system is very sensitive and requires very clean

analog voltages to keep a clean reception and transmission. This RF requirement reigns over the power management

section of the system and creates a dilemma to the system engineer. How do you extend the battery life with “efficient

switchers” when they are so “dirty” in performance compared to “linears”?

The industry has made attempts to get away from a sole linear system shown in Fig. 10 by considering a “PWM” switcher

in front of the linear as shown if Fig. 11.

The system of Fig. 10 has the advantage of very clean voltages for the RF section, but lacks high efficiency. Specifically

as the processor voltage drops and the battery makers refine the Li-Polimer battery (which ranges from 2.7V min to 4.2V

max).

The system of Fig. 11 has the advantage of high efficiency followed by clean RF due to the linears, but lacks the ability

to turn off (turn on) fast when the system is in standby operation. This is specifically due to the PWM architecture which

uses Continuous Conduction Mode (CCM) to build up the current in the coil.

WIRELESS PORTABLE SYSTEM USING PWM SWITCHER TO IMPROVE EFFICIENCY

Power

Amp

Enable A

Enable B

Enable A

µ Controller

Enable B

Enable C

FIGURE 11: PWM Switcher embedded to improve wireless system efficiency

September 1999 TOKO, Inc.

Page 21

ADVANCED INFORMATION

TK654xx

APPLICATION INFORMATION (CONT.)

The industry is presently in a frame of mind that unless the switcher is PWM with a fixed frequency (to fix the harmonics

away from the RF), the wireless RF section will not be clean. It is the intention of this application to open the mind of system

designers to consider this new concept which addresses a real issue. Several major IC manufacturers of PWM step down

converters are taunting the “Burst Mode” capability. This can be misleading since under the burst mode, the fixed

frequency of the PWM is no longer present. (Therefore harmonics are all over the place). Furthermore, the purpose of

theBurstModeistoallowthesystemtogointoastandbymodeinordertosavebatterylife. YetthesestateoftheartPWMs

with Burst mode ability still lack in response time due to the architecture which requires the coil current to slowly build up.

This build up in current is a barrier to the present day requirements.

This Buck and Linear Wireless application proposes a system as shown in Fig. 12, which allows for all 3 important aspects

of the design:

1)

2)

3)

Clean RF

High efficiency (At full, mid, and light loads)

Low standby currents with fast “wake up” response.

The approach shown in Fig. 12 requires a new architecture for the Buck (Step down) switching converter with very fast

transient characteristics, specifically during the transition from a Buck mode to Linear mode while a RF transmission/

reception is eminent or during a wake up out of standby mode.

WIRELESS PORTABLE SYSTEM USING BUCK AND LINEAR REGULATORS

Power

Amp

Buck

Enable

Buck

*

LDO

Linear

Enable

Linear

Transmit

Receive

µ Controller

* Not necessary if LDO is active low

FIGURE 12: Buck and Linear embedded to improve wireless system efficiency, standy time, and clean RF

Page 22

September 1999 TOKO, Inc.

ADVANCED INFORMATION

TK654xx

APPLICATION INFORMATION (CONT.)

Toko Inc. has come up with such a proprietary architecture implemented in their TK654XX switching step down converter.

This device is full of features as itemized in the following section:

TK654XX Features

1)

2)

Minimum pin count. Only 6 pins in a SOT23L package

Minimum external components required:

Coil and Filter cap

3)

Synchronous Rectification

4)

5)

Extremely low operating current (25uA).

18uA Standby Currents

6)

7)

Internal power devices good for greater than 200mA loads

Inherent short circuit protection

8)

No instabilities

9)

Fast transient response

10)

11)

12)

13)

14)

15)

16)

High efficiencies up to 95%

Regulation down to 1.8V

Proprietary architecture specifically aims at low ripple voltage.

Low Dropout operation (100% Duty Cycle)

Designed for battery operated equipment

Battery Monitor included

Easy to design with (Reduce the coil to increase the load current)

Explanation of Figs. 10, 11, 12 follows:

Figure 10, shows a battery operated system with communications capability. The microcontroller is programmed to turn

on / off the Linear Low Dropout regulators (LDOs) at the appropriate time. This enabling capability is useful in extending

the battery life. Please note the LDO C, which powers the microcontroller is always active.

Figure 11, takes advantage of LDO C having to be active continuously and replaces it with a PWM step down controller.

Though the PWM is always active like the LDO C of Figure 10, the PWM is more efficient and therefore is penetrating the

Wireless market in order to increase battery life. It must be pointed out in Figure 11, the role of the LDOs is important to

maintain the clean voltages for Transmission and reception modes. Figure 11 also points out that if there is small activity

withthemicrocontrollerwhichcontrolstheotherLDOs, thesystemcouldtriptothe“BurstMode”tauntedbysemiconductor

manufacturers. This mode is intended to reduce the current consumption of the PWM and increase the overall battery

life. Unfortunately, the speed that this Burst mode-to-PWM mode can react in is not very fast. Those systems, which are

compromised to increase response time, will inevitably hurt in ripple and therefore noise performance.

Figure 12, replaces the PWM with a Buck (step down) converter which has a unique architecture to respond very fast from

“Burst mode” to full load operation and a linear in parallel, rather than in series which can be enabled at the time the system

requires to transmit or receive. It is only due to the clean RF that the LDO is necessary. The majority of the time these

wireless systems are in a mode which can operate with some noise in the main voltage line. Some readers may have

noticed that Figure 12 only requires 1 LDO versus 3 LDOs in Figure 11. This principal may point out that the overall system

may turn out to be more cost effective. The system shown in Figure 12, therefore not only extends the overall battery life

by allowing the system to go into standby modes where the overall current is in the order of 25 uA, but at full load can run

in the 95% efficiency (no Transmission / Receive mode). Figure 12 can maintain the clean RF requirements for wireless

communications and reduce the overall cost.

September 1999 TOKO, Inc.

Page 23

ADVANCED INFORMATION

TK654xx

APPLICATION INFORMATION (CONT.)

Wireless Application Extend battery life, yet keep RF clean

Application results with waveforms for TK65430 in a Buck and Linear Mode

Figure 13 is a schematic of an application board available from Toko as APO14-99 from which the results shown

below were obtained. This application uses the TK11330 Low Dropout Regulator with the control function enabling

the regulator on when this control pin is low.

LBO

OUT

SW

SB

V

GND

TK65430

Note B

100 µH

V

IN

3.0 V

100 µF

Note A: This is a low ESR

(80 mΩ) capacitor from

Note A

AVX TPSD107 M010R0080

V

IN

Control

GND

TK11330

Note B: Coil used to obtain

waveforms was D63LCB type

A921CY-101M from Toko

V

OUT

Noise

Bypass

10 µF

1000 pF

Transmit/

Receive

V

IN

FIGURE 13: BUCK AND LINEAR SCHEMATIC

V

IN

C

10 µF

GND

IN

TK654xx

1

TK113xxBM

1

CON

C

N

1000pF

D

1

Optional

875FU-xxxM

C

L

100 µF

V_OUT

FIGURE 14: BUCK AND LINEAR APPLICATION BOARD LAYOUT

Page 24

September 1999 TOKO, Inc.

ADVANCED INFORMATION

TK654xx

APPLICATION INFORMATION (CONT.)

TK65430 in a Buck and Linear Mode

During the transient response between the “Buck” and “Linear” control modes the output voltage needs to stay within

the regulation requirements.

The following scope pictures show the changes in the output voltage during these transients. As can be seen, the

maximum drop is about 80 mV and maximum overshoot is negligible.

In switching from the “Buck” mode to the “Linear” mode the settling time is less than 250 µsec over the supply range

of 5 V to 3.2 V for this 3.0 V application.

V_IN= 5 V I_OUT= 100 mA

V_IN= 3.2 V I_OUT= 100 mA

Full Cycle

Switching to Linear

September 1999 TOKO, Inc.

Page 25

ADVANCED INFORMATION

TK654xx

APPLICATION INFORMATION (CONT.)

V_IN= 5 V I_OUT= 100 mA

V_IN= 3.2 V I_OUT= 100 mA

Switching to Buck

Characteristics of this application under lighter loads but similar supply range are shown below.

V_IN= 3.2 V I_OUT= 20 mA

V_IN= 5 V I_OUT= 20 mA

Full Cycle

In conclusion, the ability to provide a clean signal during transmission/reception can be done with linear regulators in a

predictable way, the novelty comes in considering the Buck and Linear concept which has the advantage of high

efficiency while not compromising the linear regulator’s low noise characteristics.

The overall effect being longer battery life while maintaining low RF interference in a wireless system.

Page 26

September 1999 TOKO, Inc.

ADVANCED INFORMATION

NOTES

TK654xx

September 1999 TOKO, Inc.

Page 27

ADVANCED INFORMATION

PACKAGE OUTLINE

TK654xx

Marking Information

SOT23L-6

Marking

+0.15

- 0.05

0.4

TK65418

*TK65419

*TK65420

TK65421

*TK65422

*TK65423

TK65424

TK65425

*TK65426

TK65427

*TK65428

*TK65429

TK65430

*TK65431

*TK65432

TK65433

418

419

420

421

422

423

424

425

426

427

428

429

430

431

432

433

0.1

M

0.6

6

Marking

+0.15

0.32^{- 0.05}

1

2

3

e

0.95

0.1

0.95

M

e

0.95

Recommended Mount Pad

* These voltages available upon request

+0.3

- 0.1

3.5

2.2

(3.4)

0.4

0.1

+ 0.3

3.3

Dimensions are shown in millimeters

Tolerance: x.x = ± 0.2 mm (unless otherwise specified)

Toko America, Inc. Headquarters

1250 Feehanville Drive, Mount Prospect, Illinois 60056

Tel: (847) 297-0070 Fax: (847) 699-7864

TOKO AMERICA REGIONAL OFFICES

Midwest Regional Office

Toko America, Inc.

1250 Feehanville Drive

Mount Prospect, IL 60056

Tel: (847) 297-0070

Western Regional Office

Toko America, Inc.

2480 North First Street , Suite 260

San Jose, CA 95131

Tel: (408) 432-8281

Fax: (408) 943-9790

Eastern Regional Office

Toko America, Inc.

107 Mill Plain Road

Danbury, CT 06811

Tel: (203) 748-6871

Fax: (203) 797-1223

Semiconductor Technical Support

Toko Design Center

4755 Forge Road

Colorado Springs, CO 80907

Tel: (719) 528-2200

Fax: (719) 528-2375

Fax: (847) 699-7864

Visit our Internet site at http://www.tokoam.com

The information furnished by TOKO, Inc. is believed to be accurate and reliable. However, TOKO reserves the right to make changes or improvements in the design, specification or manufacture of its

products without further notice. TOKO does not assume any liability arising from the application or use of any product or circuit described herein, nor for any infringements of patents or other rights of

third parties which may result from the use of its products. No license is granted by implication or otherwise under any patent or patent rights of TOKO, Inc.

Page 28

September 1999 TOKO, Inc.

Printed in the USA

IC-260-TK654xx

0899O0.0K


型号：	TK65429MTL/429
厂家：	TOKO, INC
描述：	STEP-DOWN CONVERTER WITH BATTERY MONITOR 带电池监视器降压转换器转换器电池监视器
文件：	总28页 (文件大小：758K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

TK65429MTL/429 [TOKO]

相关型号：

TK65430

TK65430M

TK65430MTL

TK65430MTL/430

TK65431

TK65431M

TK65431MTL

TK65431MTL/431

TK65432

TK65432M

TK65432MTL

TK65432MTL/432