Datasheet AN8011S Datasheet (Panasonic)

Voltage Regulators

0.3

(0° to 10°)

(0.15)

10.1±0.3

4.2±0.3

6.5±0.3

18

16 9

1.27

(0.605)

Seating plane Seating plane

0.40±0.25

0.1±0.1 1.5±0.2

AN8011S

2-channel step-down, step-up, or inverting use
DC-DC converter control IC

Unit: mm

■ Overview

The AN8011S is a DC-DC converter control IC
with two-channel output using the PWM method
which allows 500 kHz high-speed control.

Respecitve output operation can be completely
synchronized with each other by using the same
oscillation output.

■ Features

• PWM control frequency of 500 kHz is available.

• Wide operating supply voltage range

(V

= 3.6 V to 34 V)

CC

• Built-in 2-channel of open collector type for out-

put (A single-channel is also usable for inverted
amplification type)

• Each output can be stopped independently by the

external control .

• Built-in on/off function for the operation/stop of IC Incorporating circuit for short-circuit portection and under-

voltage lock-out (U.V.L.O.)

• The latch circuit is externally controllable.

• Low consumption current (during operation: 5 mA, during standby: 2 µA)

SOP016-P-0225A

■ Applications

• LCD displays, digital still cameras, and PDAs

■ Block Diagram

REF

V

16

V

REF

U.V.L.O.

OSC

1

CT

Latch

15

Latch

2

RT

IN+

14

Unlatch pro.

Short pro.

Unlatch pro.

On/
Off

3

On/Off

IN−1

13

Error amp.

Error amp.

4

IN−2

12

FB1

5

FB2

11

PWM1

PWM2

6

DTC1

DTC2

10

7

Out1

Out2

9

8

CC

V

GND

1

AN8011S Voltage Regulators

■ Pin Descriptions

Pin No. Symbol Description

1 CT Pin for connecting the oscillation frequency setting capacitor for triangular oscillation

circuit. Frequecy of triangular oscillation is set by connecting a capacitor between this
terminal and GND.

2 RT Resistor connection pin for setting the oscillation frequency of triangular oscillation

circuit. Frequecy of triangular oscillation is set by connecting resistance between the
pin and GND

3 On/Off "On/Off" pin for turning on/off IC. "Low" stops IC (output off) and "High" operates IC.
4IN−2 Inverted input pin for channel 2 error amplifier
5 F/B 2 Output pin for channel 2 error amplifier. Gain setting or phase compensation is per-

formed by connecting resistor or capacitor between the pin and IN−2. It is also connected
to PWM short-circuit protecion.

6 DTC 2 Pin for setting dead-time period of channel 2. The dead-time of channel 2 is set by

connecting external resistor. Soft start function can be also given by connecting capaci­tor in parallel with the external resistor. In addition, only channel 2 output can be turned
off by decreasing the pin voltage to below 0.12 V. (short-circuit protection function stop

circuit)
7 Out 2 Channel 2 open-collector type output pin. IO = 100 mA maximum
8 GND Grounding pin of signal system.
9VCCPower supply voltage application pin. It detects start voltage and stop voltages

10 Out 1 Channel 1 open-collector type output pin. IO = 100 mA maximum
11 DTC 1 Pin for setting dead-time period of channel 1. The dead-time period of channel 1 is set

by connecting external resistor. Soft start function can be also given by connecting capacitor

in parallel with the external resistor. In addition, only channel 1 output can be turned off

by decreasing the pin voltage to below 0.12 V. (short-circuit protection function stop

circuit)

12 F/B 1 Output pin for channel 1 error amplifier. Gain setting or phase compensation is per

formed by connecting resistor or capacitor between the pin and IN−1. It is also con

nected to PWM short-circuit protection.

13 IN−1 Inverted input pin for channel 1 error amplifier.
14 IN+ Pin for noninverted input of channel 1error amplifier.
15 Latch Pin for connecting the time constant setting capacitor for timer latch type short-circuit

protection circuit. The time constant for short-circuit protection is set by connecting

a capacitor between this terminal and GND.

16 V

REF

Internal reference voltage output pin (2.5 V(allowance: ±3%)). If a load of 20 mA typical

or more is applied, the overcurrent protection operates to reduce V

and switching

REF

operation stops.

2

Voltage Regulators AN8011S

■ Absolute Maximum Ratings at Ta = 25°C

Parameter Symbol Rating Unit

Supply voltage V
Power dissipation

*

Operating ambient temperature T
Storage temperature T

Note) 1 . Do not apply ecternal currents or voltages to any pins not speifically mentioned.

For circuit currents, '+' denotes current flowing into the IC, and '−' denotes current flowing out of the IC.

2*: When using the IC at Ta of 25°C or more, the power dessipation should be decreased 3.8 mW per 1°C.

CC

P

D

opr

stg

■ Recommended Operating Range

Parameter Symbol Range Unit

Supply voltage V

CC

■ Electrical Characteristics at VCC = 12 V, Ta = 25°C

Parameter Symbol Conditions Min Typ Max Unit

Reference voltage block

Output voltage V
Input regulation with input fluctuation Line VCC = 3.6 V to 34 V  320mV
Load regulation Load I
Output voltage temperature V

characteristics 1

*

Output voltage temperature V
characteristics 2

*

Overcurrent protection drive current *I

U.V.L.O. block

Circuit operation start voltage V
Hysteresis width V

Error amplifier block 1

Input offset voltage 1 V
Input current 1 I
Common-mode input voltage range V
High-level output voltage 1 V
Low-level output voltage 1 V

Error amplifier block 2

Input current 2 I
Common mode input threshold voltage
High-level output voltage 2 V
Low-level output voltage 2 V

REF

= 0 mA to 5 mA  210mV

REF

TC1Ta

TC2Ta

CC

UON

HYS

IN-O1

B1

CM

EH1

EL1

B2

= −25°C to + 25°C ±1  %

= 25°C to 85°C ±1  %

VIN+ 0.72 0.75 0.78 V

EH2

EL2

35 V

380 mW

−30 to +85 °C

−40 to +125 °C

3.6 to 34 V

2.413 2.5 2.588 V

−20  mA

2.8 3.1 3.4 V

100 200 300 mV

−6  6mV

−500 −25 100 nA

0.5  0.8 V

V

− 0.3

REF

 V

0.5 V

25  100 nA

V

− 0.3

REF

 V

0.5 V

3

AN8011S Voltage Regulators

■ Electrical Characteristics(continued) at VCC = 12 V, Ta = 25°C

Parameter Symbol Conditions Min Typ Max Unit

PWM comparator 1/2 block

High-level input threshold voltage V
Low-level input threshold voltage V
Input current I

DT-HfOSC

DT-LfOSC

DTC

Output 1/2 block

Output frequency 1 f
Frequency 1 f

OUT1CT

dv

Output duty ratio 1 Du1CT = 150 pF, RT = 20 kΩ, R
Output duty ratio 2 Du2CT = 150 pF, RT = 20 kΩ, R
Output saturation voltage 1 V
Output saturation voltage 2 V
Output leak current 1 I

Frequency temperature characteristics 1 *f
Frequency temperature characteristics 2 *f
Output frequency 2
Frequency 2

*

*

O(sat)1IO

O(sat)2IO

OLe1

dT1fOSC

dT2fOSC

f

OUT2CT

f

dv2

Short-circuit protection block

Input threshold voltage V
Latch drive voltage V
Charge current

SLTH

SLON

I

CHG

Unlatch pro. 1/2 block

Input threshold voltage V

ULTH

On/off block

Threshold voltage V

TH

Whole device

Total consumption current
Total consumption current fluctuation
Standby consumption current I
Maximum standby consumption current I

Note)*: These characteristics are theoretical values based on the IC design and are not guaranteed.

I

CC

I

CC(max.)VCC

CC(SB)VCC

CC(SB-M)VCC

= 200 kHz, duty = 100% 1.2  V

= 200 kHz, duty = 100% 0.6 V

RT = 20 kΩ−37 −34 −31 µA

= 150 pF, RT = 20 kΩ, IO = 30 mA

180 200 220 kHz

VCC = 3.6 V to 34 V −2  2%
CT = 150 pF, RT = 20 kΩ

DTC

DTC

= 24 k Ω
= 33 k Ω

40 45 50 %
65 75 85 %

= 30 mA 0.9 V
= 100 mA 1.2 V

V

= 34 V, when output 10 µA

CC

transistor is off

= 200 kHz, Ta = −30°C to +25°C
= 200 kHz, Ta = 25°C to 85°C

= 150 pF, RT = 6.6 kΩ, IO = 30 mA

±9  %
±9  %
 500  kHz

VCC = 3.6V to 34V, ±2  %
CT = 150 pF, RT = 6.6 kΩ

1.75 1.85 1.95 V

1.15 1.25 1.35 V

−120 −50 −40 µA

0.12  V

0.8  2V

VCC = 12 V, RT = 20 kΩ57mA

= 3.6 V to 34 V, RT = 20 kΩ  2mA
= 12 V, V
= 34 V, V

is down  2 µA

REF

is down  5 µA

REF

4

Voltage Regulators AN8011S

■ Terminal Equivalent Circuits

Pin No. Equivalent circuit Description I/O

1 CT: O

V

REF

16

To PWM input

OSC
comp.

2 RT: I

V

REF

16

OSC PWM

The terminal used for connecting a timing
capacitor to set oscillator frequency. Use a

I

O

capacitance value within the range of 100 pF

CT

to 0.1mF. For frequency setting method, re-

1

fer to the "Application Notes, [2] Function
descriptions" section. Use the oscillation fre-

2I

O

quency in the range of 1 kHz to 500 kHz.

The terminal used for connecting a timing
resistor to set oscillattion frequency.
Use a resistance value ranging from 5.1 kΩ
to 20 kΩ.
The terminal voltage is 0.67 V typ.

RT (= 0.67 V)

2

3 On/Off: I

The terminal for on/off control.
High-level input: normal operation
(V

ON/OFF

> 2.0 V typ.)

Low-level input: standby state
(V

ON/OFF

< 0.8 V typ.)

On/Off

3

Internal
circuit start/stop

17 kΩ

13 kΩ

The total current consumption in the standby
state can be suppressed to a value below 5 µA.

4IN−2: I

V

REF

16

The terminal for the inverted input of ch.2
error amplifier. Use a common-mode input
ranging from − 0.1 V to 0.8 V.

0.75 V

4

IN−2

5

AN8011S Voltage Regulators

■ Terminal Equivalent Circuits (continued)

Pin No. Equivalent circuit Description I/O

5 FB2: O

6 DTC2: I

7 Out2: O

V

V

V

REF

REF

REF

U.V.L.O.
output

16

16

16

I

DTC2

6

8 mA

typ.

DTC2

25 µA typ.

CT

5

FB2

CT

PWM2

PWM2

Out2

7

The output terminal of ch.2 error amplifier.
Its source current is −25 µA typ. and sink
current is 8 mA typ.
Correct the frequency characteristics of the
gain and the phase by connecting a resistor
and a capacitor between the terminal and
IN−2 terminal.

1) Terminal for connecting a resistor and a
capacitor for setting the dead-time and the
soft start period of ch.2 PWM output.
Input current I

is determined by the tim-

DTC

ing resistor RT so that dispersion, and fluc­tuation with temperature are suppressed. The
input current is −35 µA typ.
when R

I
R

DTC2

=

T

VRT

= 20 kΩ

× 1.04 (A)

T

(VRT: 0.67 V typ.)

2) The ch.2 output can be turned off by reduc­ing the terminal voltage to below 0.12 V.
(short-circuit protection function stop)

The ch.2 open-collector type (Darlington)
output terminal.
The absolute maximum rating of ouput cur­rent is 150 mA.
Use with an output current under 100 mA
normally.

8 GND: 

8

GND

9V

9

V

CC

GND pin

: 

CC

The pin to which supply voltage is applied.
Use within an operating supply voltage range
of 3.6 V to 34 V.

6

Voltage Regulators AN8011S

■ Terminal Equivalent Circuits (continued)

Pin No. Equivalent circuit Description I/O

10 Out1: O

V

REF

16

11 DTC1: I

V

REF

16

I

DTC1

U.V.L.O.
output

11

12 FB1: O

V

REF

16

CT

DTC1

25 µA typ.

CT

8 mA

typ.

12

FB1

Out1

10

PWM1

PWM1

The ch.1 open collector type (darlington)
output terminal.
The absolute maximum rating of output cur­rent is 150 mA.
Use with an output current of 100 mA or less
normally.

1) Terminal for connecting a resistor and a
capacitor for setting the dead-time and the soft
start period of ch.1 PWM output.
Input current I

is determined by the tim-

DTC

ing resistor RT so that dispersion and fluctu­ation with temperature are suppressed. The
input current is −35 µA typ, when R

VRT

I

=

DTC2

R

× 1.04 (A)

T

(VRT: 0.67 V typ.)

= 20 kΩ.

T

2) The ch.1 output can be turned off by reduc­ing the terminal voltage to below 0.12 V.
(short-circuit protection function stop)

The output terminal of ch.1 error amplifier.
Its source current is −25 µA typ. and sink
current is 8 mA typ.
Correct the frequency characteristics of the
gain and the phase by connecting a resistor
and a capacitor between the terminal and
IN−1 terminal.

13 IN−1: I

V

REF

The terminal for the inverted input of ch.1
error amplifier. Use a common-mode input
ranging from − 0.1 V to +0.8 V.

14 IN+:I

The terminal for noninverted input of ch.1

13

IN − 1

14

IN +

error amplifier. Use a common-mode input
ranging from − 0.1 V to +0.8 V.

7

AN8011S Voltage Regulators

■ Terminal Equivalent Circuits (continued)

Pin No. Equivalent circuit Description I/O

15 Latch: O

V

REF

16

I

CHG

4.2 kΩ

typ.

10kΩ
typ.

30 kΩ

typ.

1.25 V
typ.

Latch

S
R

Q

Terminal for connecting the time constant
setting capacitor for timer latch short-circuit
protection circuit. The charge current I

CHG

is

about −80 µA.

1.25 V
typ.

15

Latch

16 V

V

CC

9

V

overcurrent

REF

detection

Bias to
other blocks

V

16

REF

:O

REF

The output terminal for the reference voltage
(2.5 V typ.).
Use it with a load current of −1 mA or under.
The terminal has a built-in short-circuit pro­tection circuit, and the short-circuit current
is −20 mA typ.
Use the terminal for setting the reference in­put of the error amplifier.

8

Voltage Regulators AN8011S

■ Application Notes

[1] Main characteristics

Reference voltage temperature characteristics Maximum duty ratio temperature characteristics

2.500

54

2.495

(V)

REF

2.490

2.485

Reference voltage V

2.480

−20 0 20 40 60 80

−40 100

Ambient temperature Ta (°C)

53

52

51

50

Maximum duty ratio Du(45) (%)

49

−20 0 20 40 60 80

−40 100

Ambient temperature Ta (°C)

Output frequency temperature characteristics DTC pin voltage  Output duty ratio

210

209

208

207

(kHz)

OUT

206

205

204

203

Output frequency f

202

201

200

−20 0 20 40 60 80

−40 100

Ambient temperature Ta (°C)

100

90

80

70

60

50

f

= 500 kΩ

40

30

Output duty ratio (%)

20

10

OUT

0

0

f

= 200 kΩ

OUT

0.5 1 1.5

DTC pin voltage (V)

Output frequency characteristics

500

100

(kHz)

Output frequency f

OUT

10

0

10

RT = 10 kΩ

2

R

T

= 20 kΩ

= 5.1 kΩ

R

T

3

10

C

T

(pF)

4

10

5

10

9

AN8011S Voltage Regulators

■ Application Notes (continued)

[2] Function descriptions

1. Reference voltage block
This block is composed of the band gap circuit, and outputs the temperature compensated 2.5 V reference

voltage to the V
used as the operating power supply for the IC inside. It is possible to take out a load current of up to −3 mA. Also,
an overcurrent portection circuit is built in for the load, thereby protecting the IC from destruction when V
terminal is short circuited.

2. Triangular wave oscillation block
The triangular wave which swings from the wave peak of approximately 1.4 V to the wave bottom of

approximately 0.4 V will be generated by connecting a timing capacitor and a resistor to the CT terminal and RT
terminal respectively. The oscillation frequency can be freely decided by the value of C
externally. The triagular wave is connected with the inverted input of PWM comparator of the IC inside.

3. Error amplifier block
This block detects the output voltage of DC-DC conveter, and inputs the signal amplified by the PNP transistor

input type differential amplifier to the PWM comparator.

The common-mode input voltage range is − 0.1 V to 0.8 V, and is a voltage obtained by dividing the reference

voltage with resistors.

Also, it is possible to perform the gain setting and the phase compensation arbitrarily by connecting the

feedback resistor and the capacitor from the error amplifier output terminal to the inverted input terminal.

The output voltage V

noninverted input terminal as shown in figure 1. 1), and the output voltage V
connecting to the inverted input terminal as shown in figure 1. 2). The output voltages in each of these cases are
given in the following equations.

V

= VIN ×

OUT1

= V

V

IN+

V

OUT1

R1 R3

R2 R4

terminal. The reference voltage is stabilized when the supply voltage is 3.6 V or higher, and

REF

and RT connected

T

, if positive, is obtained by connecting the resistor-divided reference voltage to the

OUT

, if negative, is obtained by

OUT

REF

V

IN+
IN−1

R1 + R2

R2 R3

R1 + R2

×

R2 R1 + R2

REF

16

Error amp.1 Error amp.1

14

PWM comparator
input

13

R

NF

12

FB1

V

V

OUT1

IN−1

= − (V

= V

REF

V

R1 R3

IN+
IN−1

R2 R4

REF

×

REF

− V

16

14
13

R2

IN-1

R

NF

) ×

R3 + R4

12

PWM comparator
input

FB1

+ V

REF

REF

C

NF

1) Positive output
Figure 1. Connection method of error amplifier 1

The output voltage of channel 2 V
exclusively for positive voltage ouput, and
method of connection is as shown in figure 2.

V

OUT2

= 0.75 ×

R1 + R2

R2

10

OUT2

V

OUT1

C

NF

2) Negative output

is

V

OUT2

R1

FB2

5

NF

NF

C

R

IN−2

R3

0.75V

V

: 2.5 V

REF

Error amp.2

PWM comparator input

4

R2

R4

Figure 2. Cnnection method of error amplifier 2

Voltage Regulators AN8011S

■ Application Notes (continued)

[2] Function descriptions (continued)

4. Timer latch short-circuit protection circuit
This circuit protects the external main swiching devices, switching diodes, choke coils, and etc. from

destruction or deterioration if overload or short-circuit of power supply output lasts for a certain time.

The timer latch type short-circuit protection circuit detects the output level of each error amplifier, and when

the ouput level of either one or both of the error amplifiers exceeds 1.85 V typical, the timer circuit is actuated, and
initiates charging the external capacitor for protection enable.

If the ouput of the error amplifier does not return to a normal voltage range by the time when the voltage of

this capacitor reaches 1.25 V, it sets the latch circuit, cuts off the ouput drive transistor, and sets the dead time to
100%.

5. Low input voltage malfunction prevention circuit (U.V.L.O.)
This circuit protects the system from destruction or deterioration due to control malfunction caused by the

supply voltage reduction in the transient state of power on or off.

The low input voltage malfunction prevention circuit detects the internal reference voltage according to the

supply voltage level, and cuts off the output drive transistor by resetting the latch circuit, thereby setting the dead­time to 100% and keeping the latch terminal low.

6. PWM comparator block
The PWM comparators, each has one inverted input, and two noninverted inputs, and controls the on-period

of output pulse in accordance with the input voltage. It turns on the output transistor during the period when the
triangular wave of C

The dead-time is set by the addition of a resistor between the DTC terminal and GND. By the addition of a

capacitor in parallel with the external resistor R
of the ouput pulse by the RC time constant when the power supply is turned on starts to work.

7. Output block
The ouput drive transistor is of open-collector type output connected in Darlington circuit of emitter common

GND. The breakdown voltage of the collector ouput terminal is 34 V and it is possible to obtain up to 100 mA
ouput current.

8. Remote circuit
It is possible to switch on/off the IC control by an external control signal. When the on/off terminal voltage is

lowered to a value below approximately 0.8 V, the internal reference voltage goes down, thereby the IC control
is stopped and the circuit current is decreased to 5 µA or less. When the on/off terminal voltage is increased to a
value higher than approximately 2.0 V, the internal reference voltage raises and the control operation is started.

terminal is lower than either the error amplifier ouput voltage or the DTC terminal voltage.

T

, the soft start function which gradually extends the on-period

DTC

[3] The time constant setting method for timer latch type short-circuit protection circuit

Figure 3 shows the block diagram of the protection latch circuit. The comparator for short-circuit protection

compares the output voltage of error amplifier V

with the reference voltage (1.85 V) at all the time. When the load

FB

conditions of DC-DC converter output is stabilized, there is no fluctuation of error amplifier output, and the short­circuit protection comparator also keeps the balance. At this moment, the switch SW1 will be in the off state, and the
latch terminal voltage will be kept at approximately 0.9 V typical.

When the load conditions suddenly change, and high-level signal (1.85 V typical of higher) is inputted from the
error amplifier to the noninverted input of the short-circuit protection comparator, the short-circuit protection com­parator outputs the high-level signal. This signal turns on the switch SW1, and the charging to the capacitor C
connected externally to the latch terminal is started with a current of 80 µA typical.

When the external capacitor C

is charged up to approximately 1.25 V typical, the latch circuit is set and the under-

S

voltage lock-out circuit (U.V.L.O.) is enabled, thereby the ouput drive transistor is cut off and the dead-time is set to
100%.

Once the under-voltage lock-out circuit (U.V.L.O.) is enabled, the latch circuit will not be reset unless the power
supply is switched off.

S

11

AN8011S Voltage Regulators

f

■ Application Notes (continued)

[3] The time constant setting method for timer latch type short-circuit protection circuit (continued)

V

REF

I

CHG

80 µA typ.

5

FB2

Latch comp.

12

FB1

1.85 V

When the power supply is turned on, the output is considered to be short-circuited state, so that the error amplifier
output becomes high-level, then SW1 becomes on state and the charging starts. It is necessary to set the external
capacitor so as to start up the DC-DC converter output voltage before setting the latch circuit in the later stage.

Especially, pay attention to the delay of the start-up time when applying the soft-start.

SW1

30 kΩ
typ.

10 kΩ
typ.

4

4.2 kΩ typ.

1.25 V
typ.

SR

Latch

Latch
C

S

Figure 3. Short-circuit protection circuit

R

Cut output of

U.V.L.O.

[4] Explanation of unlatch protection circuit operation

Figure 4 shows the block diagram of the unlatch protection circuit. It is possible to suppress FB terminal, the error
amplifier output terminal of the channel, to low by setting DTC terminal to 0.12 V or less through external signal.
Consequently, by controlling the DTC terminal voltage, it is possible to operate only one channel, or to start and stop
each channel in any required sequence.

FB1

IN+

IN−1

DTC1

12

14
13

11

Error amp.1

I

DTC1

To PW1

Unlatch protection
comp.1

To PW2

Unlatch protection
comp.2

Error amp.2

I

DTC2

5

4

6

FB2

IN−2

DTC2

0.12 V typ.0.12 V typ.

Figure 4. Unlatch protection circuit

12

Voltage Regulators AN8011S

■ Application Notes (continued)

[5] Triangular wave oscillation circuit

• Oscillation frequency setting method

The waveform of triangular wave oscillation is obtained by charging and discharging of the constant current I
from the external timing capacitor CT which is connected to CT terminal. The constant current is set by the externally
attached timing resistor R

The peak value of the wave V
value of the wave V
typical and 0.4 V typical respectively.

The oscillation frequency f
following formula;

1

f

=

OSC

t

(typ.)
Where IO = 2 ×

R

Because V
f

=

OSC

C

(typ.)

=

+ t2 2 × CT × (V

1

VRT

− V

CTH

0.67
× R

T

T

The ouput frequency f

[6] Dead-time (maximum duty) setting method

The setting of the dead-time is conducted by adjusting the DTC terminal voltage V
the DTC terminal provides a constant current output through the resistor R
resistor R

DTC

.

The output duty ratio Du and the DTC terminal voltage V
oscillation frequency f

Pay attention to the peak volue and the trough value of triangular wave because the overshoot and undershoot
voltages depend on the frequency.

.

T

and the trough

CTH

are fixed at approximately 1.4 V

CTL

is obtained by the

OSC

I

T

CTL

O

0.67

= 2 ×

R

= 1V

CTH

− V

)

CHL

T

[Hz]

is equal to f

OUT

is 200 kHz, the output duty ratio is 0% at V

OSC

since it is PWM-controlled.

OSC

V

CTH

= 1.4 V typ.

V

t

1

Charging

t

2

Discharging

CTL

= 0.4 V typ.

T

Figure 5. Triangular wave oscillation waveform

as shown in figure 6. Since

DTC

, V

is adjusted by attaching the external

T

DTC

are expressed by the following formula. When the

DTC

= 0.42 V, and 100% at V

DTC

= 1.35 V.

DTC

O

waveform

C

T

DTC waveform

t

OFF

V

CTH

V

DTC

V

t

ON

CTL

V

I

REF

DTC

I

DTC

=

CT
FB

V

RT

R

× 1.04 [A]

T

PWM

Out waveform

Off OffOn

DTC

t

=

=

= I
= V

ON

tON + t
V

CTH

V

CTH

DTC

×

RT

−V

× R

OFF

−V

R

DTC
CTL

DTC

DTC

R

T

×

100 [%]

×

100 [%]

× 1.04 [V]

ex.) When f

R

DTC

= 200 kHz (RT = 20 kΩ, CT = 150 pF),

OSC

V

≈1.4 V(typ.) VRT≈ 0.67 V(typ.)

CTH

V

≈0.4 V(typ.) I

CTL

C

DTC

DTL

≈ 35 µA (typ.)

Du

(typ.)

V

DTC

(typ.)

Figure 6. Dead-time setting method

When the capacitor C

is added in parallel with the external resistor R

DTC

, the soft start function gradually extends

DTC

the on-period of the output pulse when the power supply is turned on. This prevents the overshoot of the DC-DC
converter output.

13

AN8011S Voltage Regulators

■ Application Notes (continued)

[7] Timing chart

3.1 V typ.

Lock-out release

Power supply

on

Dead-time voltage (V

Output transistor collector
waveform(OUT)

DT

Supply voltage (V

Reference voltage (V

Error amplifier output (FB)

Triangular wave (CT)

)

)

CC

)

REF

Latch terminal voltage

Soft start operation Maximum duty

Figure 7. Operation waveform of PWM comparator

3.6 V

2.5 V

1.83 V

1.3 V

0.9 V

0.40 V

0.03 V
High

Low

Reference voltage (V

Short-circuit protection input threshold level
Comparator threshold level

DTC terminal voltage

Latch terminal voltage

Error amplifier ouput (FB)

Triangular wave (CT)

Output transistor collector waveform
(OUT)

Short-circuit protection comparator
output

REF

)

Figure 8. Operation waveform of short-circuit protection

2.5 V

1.85 V

1.4 V

0.9 V

0.40 V

High

Low

t

PE

High

Low

14

Voltage Regulators AN8011S

■ Application Circuit Examples

• Application circuit example 1

6 kΩ

14 kΩ

23 kΩ

7 kΩ

REF

V

16

V

REF

U.V.L.O.

OSC

1

150 pF

CT

Latch

15

Latch

2

20 kΩ

Short pro.

RT

On/
Off

IN+

14

3

On/Off

3 V

0.01 µF

120 kΩ

IN−1

13

Error

amp.

Unlatch pro.

Unlatch pro.

Error
amp.

4

IN−2

120 kΩ

0.01 µF

3 V

FB1

12

5

FB2

0.1 µF

PWM1

0.1 µF

DTC1

11

PWM2

6

DTC2

33 kΩ

33 kΩ

V

Out1

10

7

Out2

SBD

CC

SBD

CC

V

9

8

GND

−5 V

f = 200 kHz
Duty = 75%

5V

7

3 V

SBD

5 V

25.5 kΩ

4.5 kΩ

To pin 4

25.5 kΩ

4.5 kΩ

15

AN8011S Voltage Regulators

■ Application Circuit Examples

• Application circuit example 2

10 µF

2.5 V

REF

V

16

V

REF

U.V.L.O.

OSC

1

150 pF

CT

Latch

15

Latch

2

20 kΩ

Short pro.

On/
Off

RT

VIN = 7 V

IN+

14

Unlatch pro.

Unlatch pro.

3

On/Off

R

0.01 µF

120 kΩ

IN−1

13

Error
amp.

Error
amp.

4

IN−2

120 kΩ

0.01 µF

VCC = 7 V

FB1

12

5

FB2

0.1 µF

PWM1

PWM2

0.1 µF

500 Ω

500 Ω

DTC1

11

6

DTC2

33 kΩ

Out1

10

7

Out2

33 kΩ

100 Ω

VCC = 7 V

CC

V

9

8

GND

100 Ω

3.3 V

5 V

16

25.5 kΩ

0.75 V

4.5 kΩ