Kingbor KB3426-ADJ, KB3426B-1.8, KB3426B-3.3 Schematic

Kingbor Technology Co.,Ltd

TEL:(86)0755-26508846 FAX:(86)0755-26509052

KB3426

FEATURES

■

High Efficiency: Up to 96%

■

Very Low Quiescent Current: Only 20µA During Operation

■

800mA Output Current

■

2.5V to 6.5V Input Voltage Range

■

1.5MHz Constant Frequency Operation

■

No Schottky Diode Required

■

Low Dropout Operation: 100% Duty Cycle

■

0.6V Reference Allows Low Output Voltages

■

Shutdown Mode Draws )1µA Supply Current

■

Current Mode Operation for Excellent Line and Load Transient Response

■

Overtemperature Protected

■

Low Profile (1mm) SOT23-5 Package

APPLICATIONS

■

Cellular Telephones

■

Personal Information Appliances

■

Wireless and DSL Modems

■

Digital Still Cameras

■

MP3 Players

■

Portable Instruments

1.5MHz,

800mA

Synchronous Step-Down

Regulator in

SOT23-5

DESCRIPTION

The KB3426 is a high efficiency monolithic synchronous buck regulator using a constant frequency, current mode architecture. The device is available in an adjustable version and fixed output voltages of 1.8V and 3.3V. Supply current during operation is only 20µA and drops to ) 1µA in shutdown. The 2.5V to 5.5V input voltage range makes the KB3426 ideally suited for single Li-Ion battery-powered applications. 100% duty cycle provides low dropout operation, extending battery life in portable systems. Automatic Burst Mode operation increases efficiency at light loads, further extending battery life.

Switching frequency is internally set at 1.5MHz, allowing the use of small surface mount inductors and capacitors.

The internal synchronous switch increases efficiency and eliminates the need for an external Schottky diode. Low output voltages are easily supported with the 0.6V feedback reference voltage. The KB3426 is available in a low profile (1mm) SOT23-5 package.

TYPICAL APPLICATION

V

3.6V

TO 6.5V

IN

+

C

IN

4.7µF Tan

4

V

IN

KB3426-3.3

1

RUN

V

GND

2

Figure 1a. High Efficiency Step-Down Converter

SW

OUT

4.7µH

3

5

C

OUT

10µF CER

V

OUT

3.3V 800mA

95

VIN = 3.6V

90

85

80

75

EFFICIENCY (%)

70

65

60

0.1 10 100 1000

VIN = 3.8V

VIN = 4.2V

1 OUTPUT CURRENT (mA)

V

OUT

Figure 1b. Efficiency vs Load Current

= 3.3V

1

Kingbor Technology Co.,Ltd

TEL:(86)0755-26508846 FAX:(86)0755-26509052

KB3426

ABSOLUTE MAXIMUM RATINGS

(Note 1)

Input Supply Voltage .................................. –0.3V to 6.5V

RUN, VFB Voltages ..................................... – 0.3V to V

IN

SW Voltage .................................. –0.3V to (VIN + 0.3V)

P-Channel Switch Source Current (DC) ............. 800mA

N-Channel Switch Sink Current (DC) ................. 800mA

PACkAGE/ORDER INFORMATION

ORDER PART

TOP VIEW

Marking

RUN 1

GND 2

SW 3

S5 PACKAGE

5-LEAD PLASTIC SOT-23

T

= 125°C, eJA = 250°C/ W, eJC = 90°C/ W

JMAX

5 V

4 V

FB

IN

NUMBER

KB3426-ADJ

Top Marking

A17x

A16x

x: date code

Peak SW Sink and Source Current ........................ 1.3A

Operating Temperature Range (Note 2) .. – 40°C to 85°C

Junction Temperature (Note 3)............................ 125°C

Storage Temperature Range ................ –65°C to 150°C

Lead Temperature (Soldering, 10 sec)................. 300°C

ORDER PART

TOP VIEW

Marking

RUN 1

GND 2

SW 3

S5 PACKAGE

5-LEAD PLASTIC SOT-23

T

= 125°C, eJA = 250°C/ W, eJC = 90°C/ W

JMAX

5 V

4 V

OUT

IN

NUMBER

KB3426B-3.3

Top Marking

A33x

KB3426B-1.8

Top Marking

A37x

x: date code

ELECTRICAL CHARACTERISTICS

The● denotes specifications which apply over the full operating temperature range, otherwise specifications are TA = 25°C. VIN = 3.6V unless otherwise specified.

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

I

VFB

V

FB

6V

FB

V

OUT

6V

OUT

I

PK

V

LOADREG

V

IN

I

S

f

OSC

R

PFET

R

NFET

I

LSW

Feedback Current ● ±30 nA

Regulated Feedback Voltage KB3426 (Note 4) TA = 25°C 0.5880 0.6 0.6120 V

KB3426 (Note 4) 0 °C T KB3426 (Note 4) –40 °C ) T

Reference Voltage Line Regulation VIN = 2.5V to 5.5V (Note 4) ● 0.04 0.4 %/V

Regulated Output Voltage KB3426-1.8, I

KB3426-3.3, I

Output Voltage Line Regulation VIN = 2.5V to 5.5V ● 0.04 0.4 %/V

Peak Inductor Current VIN = 3V, VFB = 0.5V or V

Duty Cycle < 35%

Output Voltage Load Regulation 0.5 %

Input Voltage Range ● 2.5 6.5 V

Input DC Bias Current (Note 5) Active Mode V Sleep Mode V Shutdown V

Oscillator Frequency VFB = 0.6V or V

R

of P-Channel FET ISW = 100mA 0.4 0.5 1

DS(ON)

R

of N-Channel FET ISW = –100mA 0.35 0.45 1

DS(ON)

SW Leakage V

= 0.5V or V

FB

= 0.62V or V

FB

= 0V, VIN = 4.2V 0.1 1 µA

RUN

= 0V or V

V

FB

= 0V, VSW = 0V or 5V, VIN = 5V ±0.01 ±1 µA

RUN

OUT OUT

OUT

) 85°C 0.5865 0.6 0.6135 V

A

) 85°C ● 0.5850 0.6 0.6150 V

A

= 100mA ● 1.746 1.800 1.854 V = 100mA ● 3.234 3.300 3.366 V

= 90%, 0.75 1 1.25 A

OUT

= 90%, I

= 103%, I

= 100% ● 1.2 1.5 1.8 MHz

= 0V 210 kHz

= 0A 300 400 µA

LOAD

= 0A 20 35 µA

LOAD

2

Kingbor Technology Co.,Ltd

TEL:(86)0755-26508846 FAX:(86)0755-26509052

KB3426

ELECTRICAL CHARACTERISTICS

The ● denotes specifications which apply over the full operating temperature range, otherwise specifications are TA = 25°C.

= 3.6V unless otherwise specified.

V

IN

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

V

I

RUN

RUN Threshold

RUN Leakage Current ● ±0.01 ±1 µA

●

0.3 1 1.5 V

Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired.

Note 2: The KB3426E is guaranteed to meet performance specifications from 0°C to 70°C. Specifications over the –40°C to 85°C operating temperature range are assured by design, characterization and correlation with statistical process controls.

Note 3: T dissipation P

Note 4: The KB3426 is tested in a proprietary test mode that connects V

Note 5: Dynamic supply current is higher due to the gate charge being

is calculated from the ambient temperature TA and power

J

according to the following formula:

D

KB3426: T

to the output of the error amplifier.

FB

delivered at the switching frequency.

TYPICAL PERFORMANCE CHARACTERISTICS

(From Figure1a Except for the Resistive Divider Resistor Values)

Efficiency vs Input Voltage

100

I

95

90

85

80

75

70

EFFICIENCY (%)

65

60

55

50

= 100mA

OUT

I

= 1mA

OUT

I

= 650mA

OUT

I

= 0.1mA

OUT

V

= 1.8V

OUT

2

3

4

INPUT VOLTAGE (V)

I

OUT

= 10mA

5

6

Efficiency vs Output Current

95

V

= 1.2V

OUT

90

85

80

75

EFFICIENCY (%)

70

65

60

0.1 10 100 1000

VIN = 2.7V

VIN = 4.2V

VIN = 3.6V

1

OUTPUT CURRENT (mA)

= TA + (PD)(250°C/W)

J

Efficiency vs Output Current

95

V

90

85

80

75

EFFICIENCY (%)

70

65

60

0.1 10 100 1000

= 1.5V

OUT

VIN = 2.7V

VIN = 4.2V

VIN = 3.6V

1 OUTPUT CURRENT (mA)

Efficiency vs Output Current

100

V

= 2.5V

OUT

95

VIN = 2.7V

90

85

80

75

EFFICIENCY (%)

70

65

60

0.1 10 100 1000

VIN = 3.6V

VIN = 4.2V

1 OUTPUT CURRENT (mA)

Reference Voltage vs Temperature

0.614 VIN = 3.6V

0.609

0.604

0.599

0.594

REFERENCE VOLTAGE (V)

0.589

0.584

–50

–25 0

TEMPERATURE (°C)

50 100 125

25 75

Oscillator Frequency vs Temperature

1.70 VIN = 3.6V

1.65

1.60

1.55

1.50

1.45

FREQUENCY (MHz)

1.40

1.35

1.30

–50

–25 0

TEMPERATURE (°C)

50 100 125

25 75

3

Kingbor Technology Co.,Ltd

TEL:(86)0755-26508846 FAX:(86)0755-26509052

TYPICAL PERFORMANCE CHARACTERISTICS

(From Figure1a Except for the Resistive Divider Resistor Values)

KB3426

Oscillator Frequency vs Supply Voltage

1.8

1.7

1.6

1.5

1.4

OSCILLATOR FREQUENCY (MHz)

1.3

1.2

0.7

0.6

0.5

0.4

(1)

0.3

DS(ON)

R

0.2

0.1

0

2

R

–50

34 56

SUPPLY VOLTAGE (V)

vs Temperature Supply Current vs Supply Voltage Supply Current vs Temperature

DS(ON)

VIN = 4.2V

MAIN SWITCH SYNCHRONOUS SWITCH

–25 0

VIN = 3.6V

25 75

TEMPERATURE (°C)

VIN = 2.7V

50 100 125

Output Voltage vs Load Current

1.844 VIN = 3.6V

1.834

1.824

1.814

1.804

1.794

OUTPUT VOLTAGE (V)

1.784

1.774

100 900

0

200 300 400 500 600 700 800

LOAD CURRENT (mA)

50

V

= 1.8V

OUT

45

40

35

30

25

20

15

SUPPLY CURRENT (µA)

10

= 0A

I

LOAD

5

0

2

3

4

SUPPLY VOLTAGE (V)

R

) vs Input Voltage

DS(ON

0.7

0.6

0.5

0.4

(1)

0.3

DS(ON)

R

0.2

0.1

0

10

23

50

VIN = 3.6V

45

= 1.8V

V

OUT

= 0A

I

LOAD

40

35

30

25

20

15

SUPPLY CURRENT (µA)

10

5

0

5

6

–50

–25

0

MAIN SWITCH

SYNCHRONOUS

SWITCH

46

INPUT VOLTAGE (V)

50

25

TEMPERATURE (°C)

57

100

125

75

Switch Leakage vs Temperature

300

VIN = 5.5V RUN = 0V

250

200

150

100

SWITCH LEAKAGE (nA)

50

SYNCHRONOUS SWITCH

0

–50

–25 0

TEMPERATURE (°C)

MAIN SWITCH

50 100 125

25 75

4

Switch Leakage vs Input Voltage

120

RUN = 0V

100

80

60

40

SWITCH LEAKAGE (pA)

20

0

SYNCHRONOUS

234

1

INPUT VOLTAGE (V)

SWITCH

MAIN

SWITCH

56

SW

5V/DIV

V

OUT

100mV/DIV

AC COUPLED

200mA/DIV

Burst Mode Operation

I

L

V I

LOAD

OUT

= 1.8V

= 50mA

4µs/DIVVIN = 3.6V

Kingbor Technology Co.,Ltd

TEL:(86)0755-26508846 FAX:(86)0755-26509052

TYPICAL PERFORMANCE CHARACTERISTICS

(From Figure 1a Except for the Resistive Divider Resistor Values)

KB3426

RUN

2V/DIV

V

OUT

2V/DIV

I

LOAD

500mA/DIV

Start-Up from Shutdown

IN

V

OUT

I

LOAD

= 3.6V

= 1.8V

= 800mA

40µs/DIVV

Load Step

V

OUT

100mV/DIV

AC COUPLED

I

L

500mA/DIV

I

LOAD

500mA/DIV

V

OUT

100mV/DIV

AC COUPLED

500mA/DIV

I

LOAD

500mA/DIV

Load Step

I

L

= 3.6V

IN

V

OUT

I

LOAD

= 1.8V

= 0mA TO 800mA

20µs/DIVV

V

OUT

100mV/DIV

AC COUPLED

500mA/DIV

I

LOAD

500mA/DIV

Load Step

I

L

V

OUT

100mV/DIV

AC COUPLED

500mA/DIV

I

LOAD

500mA/DIV

Load Step

I

L

= 3.6V

IN

= 1.8V

V

OUT

I

LOAD

20µs/DIVV

= 50mA TO 800mA

= 3.6V

IN

V

= 1.8V

OUT

= 100mA TO 800mA

I

LOAD

20µs/DIVV

PIN FUNCTIONS

RUN (Pin 1): Run Control Input. Forcing this pin above

1.5V enables the part. Forcing this pin below 0.3V shuts down the device. In shutdown, all functions are disabled drawing <1µA supply current. Do not leave RUN floating.

GND (Pin 2): Ground Pin.

SW (Pin 3): Switch Node Connection to Inductor. This pin

connects to the drains of the internal main and synchronous power MOSFET switches.

= 3.6V

IN

= 1.8V

V

OUT

= 200mA TO 800mA

I

LOAD

20µs/DIVV

VIN (Pin 4): Main Supply Pin. Must be closely decoupled to GND, Pin 2, with a 2.2µF or greater ceramic capacitor.

VFB (Pin 5) (kB3426): Feedback Pin. Receives the feedback voltage from an external resistive divider across the output.

V

(Pin 5) (kB3426-1.8/kB3426-3.3): Output Volt-

OUT

age Feedback Pin. An internal resistive divider divides the output voltage down for comparison to the internal reference voltage.

5

Kingbor Technology Co.,Ltd

TEL:(86)0755-26508846 FAX:(86)0755-26509052

SIMPLIFIED BLOC DIAGRAM

SLOPE

COMP

OSC

–

+

EA

–

+

VFB/V

RUN

OSC

FREQ

OUT

5

V

IN

1

0.6V REF

SHIFT

R1

R2

0.6V

FB

0.4V

–

+

S

R

RS LATCH

BURST

Q

SLEEP

SWITCHING

LOGIC

AND

BLANKING

CIRCUIT

0.65V

I

SHOOT-

–

COMP

ANTI-

THRU

KB3426

V

4

IN

+

51

SW

3

SHUTDOWN

OPERATION

(Refer to Functional Diagram)

Main Control Loop

The KB3426 uses a constant frequency, current mode step-down architecture. Both the main (P-channel MOSFET) and synchronous (N-channel MOSFET) switches are internal. During normal operation, the internal top power MOSFET is turned on each cycle when the oscillator sets the RS latch, and turned off when the current comparator, I current at which I

, resets the RS latch. The peak inductor

COMP

resets the RS latch, is controlled by

COMP

the output of error amplifier EA. When the load current increases, it causes a slight decrease in the feedback voltage, FB, relative to the 0.6V reference, which in turn, causes the EA amplifier’s output voltage to increase until the average inductor current matches the new load current. While the top MOSFET is off, the bottom MOSFET is turned on until either the inductor current starts to reverse, as indicated by the current reversal comparator I

RCMP

, or

the beginning of the next clock cycle.

+

I

RCMP

–

GND

2

Burst Mode Operation

The KB3426 is capable of Burst Mode operation in which the internal power MOSFETs operate intermittently based on load demand.

In Burst Mode operation, the peak current of the inductor is set to approximately 200mA regardless of the output load. Each burst event can last from a few cycles at light loads to almost continuously cycling with short sleep intervals at moderate loads. In between these burst events, the power MOSFETs and any unneeded circuitry are turned off, reducing the quiescent current to 20µA. In this sleep state, the load current is being supplied solely from the output capacitor. As the output voltage droops, the EA amplifier’s output rises above the sleep threshold signaling the BURST comparator to trip and turn the top MOSFET on. This process repeats at a rate that is dependent on the load demand.

6

Kingbor KB3426-ADJ, KB3426B-1.8, KB3426B-3.3 Schematic [ru]