ST ST1S09 User Manual

ST1S09

2 A, 1.5 MHz PWM step-down switching regulator with synchronous rectification

Features

■1.5 MHz fixed frequency PWM with current control mode

■2 A output current capability

■Typical efficiency: > 90%

■2 % DC output voltage tolerance

■Two versions available: power good or inhibit

■Integrated output over-voltage protection

■Non switching quiescent current: (typ) 1.5 mA over temperature range

■RDSON (typ) 100 mΩ

■Utilizes tiny capacitors and inductors

■Operating junction temp. -30 °C to 125 °C

■Available in DFN6 (3 x 3 mm) exposed pad

Description

The ST1S09 is a step-down DC-DC converter optimized for powering low output voltage applications. It supplies a current in excess of 2 A over an input voltage range from 2.7 V to 6 V.

A high PWM switching frequency (1.5 MHz) allows the use of tiny surface-mount components.

DFN6 (3 x 3 mm)

Moreover, since the required synchronous rectifier is integrated, the number of the external components is reduced to minimum: a resistor divider, an inductor and two capacitors. The Power Good function continuously monitors the output voltage. An open drain Power Good flag is released when the output voltage is within regulation. In addition, a low output ripple is guaranteed by the current mode PWM topology and by the use of low ESR SMD ceramic capacitors. The device is thermally protected and the output current limited to prevent damages due to accidental short circuit. The ST1S09 is available in the DFN6 (3 x 3 mm) package.

Table 1.	Device summary
	Order codes	Package
	ST1S09PUR	DFN6D (3 x 3 mm)
	ST1S09APUR (1)	DFN6D (3 x 3 mm)
	ST1S09IPUR	DFN6D (3 x 3 mm)

1. Available on request.

April 2010	Doc ID 13632 Rev 4	1/18
		www.st.com

ST1S09

Contents

1	Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	. 3
2	Pin configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	4
3	Maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	5
4	Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	6
5	Typical performance characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . .	8
6	Typical application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	11
7	Application information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	12
8	Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	13
9	Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	17

2/18	Doc ID 13632 Rev 4

ST1S09	Diagram

1 Diagram

Figure 1. Schematic diagram

(*) Only for ST1S09IPU

(**) Only for ST1S09PU

Doc ID 13632 Rev 4

3/18

Pin configuration	ST1S09

2 Pin configuration

Figure 2. Pin connections (top view)

ST1S09

ST1S09A

ST1S09I

	Table 2.	Pin description
	Pin n°	Symbol	Name and function
	1	FB	Feedback voltage
	2	GND	System ground
	3	SW	Switching pin
	4	VIN_SW	Power supply for the MOSFET switch
	5	VIN_A	Power supply for analog circuit
	6	INH/PG/NC	Inhibit (to turn off the device) / Power Good / Not Connected
	Exposed	GND	To be connected to PCB ground plane for optimal electrical and thermal
	Pad		performance

4/18	Doc ID 13632 Rev 4

ST1S09	Maximum ratings

3 Maximum ratings

Table 3.

Absolute maximum ratings

Symbol

Parameter

Value

Unit

VIN_SW

Positive power supply voltage

-0.3 to 7

V

VIN_A

Positive power supply voltage

-0.3 to 7

V

VINH

Inhibit voltage (I version)

-0.3 to VI + 0.3

V

SWITCH Voltage

Max. voltage of output pin

-0.3 to 7

V

VFB

Feedback voltage

-0.3 to 3

V

PG

Power Good open drain

-0.3 to 7

V

TJ

Max junction temperature

-40 to 150

°C

TSTG

Storage temperature range

-65 to 150

°C

TLEAD

Lead temperature (soldering) 10 sec

260

°C

Note:

Absolute maximum ratings are those values beyond which damage to the device may occur.

Functional operation under these conditions is not implied.

Table 4.

Thermal data

Symbol

Parameter

Value

Unit

RthJC

Thermal resistance junction-case

10

°C/W

RthJA

Thermal resistance junction-ambient

55

°C/W

Table 5.

ESD performance

Symbol

Parameter

Test conditions

Value

Unit

ESD

ESD protection voltage

HBM

2

kV

ESD

ESD protection voltage

MM

500

V

Doc ID 13632 Rev 4

5/18

Electrical characteristics	ST1S09

4 Electrical characteristics

Refer to Figure 21 application circuit VIN_SW = VIN_A = 5 V, VO = 1.2 V, C1 = 4.7 µF,

C2 = 22 µF, L1 = 2.7 µH, TJ = -30 to 125 °C (unless otherwise specified. Typical values are referred to 25 °C)

Table 6.

Electrical characteristics for ST1S09PU

Symbol

Parameter

Test conditions

Min.

Typ.

Max.

Unit

FB

Feedback voltage

784

800

816

mV

IFB

VFB pin bias current

600

nA

VI

Input voltage

IO = 10 mA to 2 A

4.5

5.5

V

UVLO

Under voltage lock out

VI

Rising

3.5

3.7

3.9

V

threshold

Hysteresis

150

mV

Over voltage protection

VO rising

1.05 VO

1.1 VO

V

OVP

threshold

Over voltage protection

VO falling

5

%

hysteresis

IOVP

Overvoltage clamping current

VO = 1.2 V

300

mA

IQ

Quiescent current

Not switching

1.5

2.5

mA

IO

Output current

VI = 4.5 to 5.5 V (1)

2

A

%V / V

I

Output line regulation

V

= 4.5 V to 5.5 V, I

O

= 100 mA (1)

0.16

%VO/

O

I

VI

%V /

I

Output load regulation

I

O

= 10 mA to 2 A (1)

0.2

0.6

%

O

O

PWMfS

PWM switching frequency

VFB = 0.65 V

1.2

1.5

1.8

MHz

DMAX

Maximum duty cycle

80

87

%

PG

Power good output threshold

0.92 VO

V

Power good output voltage low

ISINK = 6 mA open drain output

0.4

V

RDSON-N

NMOS switch on resistance

ISW = 750 mA

0.1

Ω

RDSON-P

PMOS switch on resistance

ISW = 750 mA

0.1

Ω

ISWL

Switching current limitation

(1)

2.5

2.9

3.5

A

ν

Efficiency (1)

IO = 10 mA to 100 mA, VO = 3.3 V

65

%

IO = 100 mA to 2 A, VO = 3.3 V

82

87

TSHDN

Thermal shutdown

150

°C

THYS

Thermal shutdown hysteresis

20

°C

%VO/

IO

Load transient response

IO = 100 mA to 1 A, TA = 25 °C

-10

+10

%VO

t

R

= t ≥ 200 ns (1)

F

%VO/

IO

Short circuit removal response

IO = 10 mA to IO = short,

-10

+10

%VO

T = 25 °C (1)

A

1. Guaranteed by design, but not tested in production.

6/18	Doc ID 13632 Rev 4