ST ST2S08B User Manual

Dual synchronous rectification, 1.5 A, 1.5 MHz

adjustable step-down switching regulator

Features

■ Step-down current mode PWM (1.5 MHz) DC-

DC converter

■ Adjustable output voltage from 0.8 V

■ 2 % DC output voltage tolerance

■ Synchronous rectification

■ Integrated current limit

■ Inhibit function

■ Soft-start for start delay of 800 µs typ.

■ Typical efficiency: > 80 % at V

■ 1.5 A output current capability

■ Non-switching quiescent current: max 1.5 mA

over temperature range

■ R

■ Uses tiny capacitors and inductors

■ Available in QFN12L (4 x 4 mm)

DS(ON)

150 mΩ (typ.)

OUT

= 1.2 V

ST2S08B

Datasheet − production data

QFN12L (4 x 4 mm)

ST2S08B is available in the QFN12L (4 x 4 mm)
package.

Description

The ST2S08B is a dual step-down DC-DC
converter optimized for powering low-voltage
digital cores in ODD applications and, generally,
to replace the high current linear solution when
the power dissipation may cause a high heating of
the application environment. It provides up to 1.5
A over an input voltage range of 3 V to 5.5 V. A
high switching frequency of 1.5 MHz allows the
use of tiny surface-mounted components as well
as a resistor divider to set the output voltage
value. Only an inductor and two capacitors are
required. A low output ripple is guaranteed by the
current mode PWM topology and the utilization of
low ESR SMD ceramic capacitors. The device is
thermally protected and current limited. The

Table 1. Device summary

Order code Package Packaging

ST2S08BPQR QFN12L (4 x 4 mm) Tape and reel

May 2012 Doc ID 18290 Rev 2 1/18

This is information on a product in full production.

www.st.com

18

Contents ST2S08B

Contents

1 Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

2 Pin configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

3 Maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

4 Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

5 Typical application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

6 Typical performance characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

7 General information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

8 Application information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

8.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

8.2 Programming the output voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

8.3 Inductor selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

8.4 Input and output capacitor selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

8.5 Layout considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

9 Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

10 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

2/18 Doc ID 18290 Rev 2

ST2S08B Diagram

1 Diagram

Figure 1. Schematic diagram

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Doc ID 18290 Rev 2 3/18

Pin configuration ST2S08B

2 Pin configuration

Figure 2. Pin connections (top view)

Table 2. Pin description

Pin n° Name Function

1 HV Programing pin. It must be floating or connected to GND.

2 FB2 Feedback voltage

3 GND2 Power ground

4 SW2 Switching pin

5 VIN_SW Power input voltage pin

6 SW1 Switching pin

7 GND1 Power ground

8 FB1 Feedback voltage/output voltage

9 NC Not connect

Inhibit pin:

10 INH

11 VIN_A Supply for analog circuit

12 GND_A System ground

- High device on

- Low device off

4/18 Doc ID 18290 Rev 2

ST2S08B Maximum ratings

3 Maximum ratings

Table 3. Absolute maximum ratings

Symbol Parameter Value Unit

V

IN_SW

V

V

IN_A

INH

Positive power supply voltage -0.3 to 7 V

Positive power supply voltage -0.3 to 7 V

Inhibit voltage -0.3 to 7 V

SWITCH voltage Max. voltage of output pin -0.3 to 7 V

V

FB1,2

Current into V

T

J

T

STG

T

LEAD

Feedback voltage/output voltage -0.3 to 2.5 V

pin Common mode input voltage +1 to -1 mA

FB

Max junction temperature 150 °C

Storage temperature range -65 to +150 °C

Lead temperature (soldering) 10 sec. 300 °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

R

thJC

R

thJA

Thermal resistance junction-case 10 °C/W

Thermal resistance junction-ambient 60 °C/W

Table 5. ESD performance

Symbol Parameter Test conditions Value Unit

ESD ESD protection voltage HBM-DH11C 4 kV

Doc ID 18290 Rev 2 5/18

Electrical characteristics ST2S08B

4 Electrical characteristics

V
T

Table 6. Electrical characteristics

= V

IN_SW

= -30 to 125 °C, unless otherwise specified. Typical values refer to 25 °C.

J

IN_A

= 5 V, V

=1.2 V, C1= 4.7 µF, C2 = C3 = 22 µF, L1 = L2 = 3.3 µH,

O1,2

Symbol Parameter Test conditions Min. Typ. Max. Unit

FB

I

FB1,2

I

I

O1,2

I

MIN

V

INH

Q

Feedback voltage 784 800 816 mV

1,2

VFB pin bias current V

Quiescent current

Output current

= 1 V 600 nA

FB

> 1.2 V, V

V

INH

V

= GND 20 µA

INH

= 3.0 to 5.5 V

V

IN

= - 30 to 85 °C

T

J

= 1 V 1.5 mA

FB

(1)

,

1.5 A

Minimum output current 1 mA

3.0 V < V

Inhibit threshold

< 5 V 1.2

IN

< 5.5 V 1.3

IN

Device OFF 0.4

I

INH1,2

%V

O1,2

ΔV

ΔV

O1,2

PWM f

D

MAX

I

SWL

I

LKN

I

LKP

R

DSon

R

DSon

η Efficiency

T

SHDN

T

HYS

- V

I

SC

1. VO= 90 % of nominal value.

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

Inhibit pin current 2 µA

/

Reference line regulation 3.0 V < V

IN

< 5.5 V 0.04

IN

Reference load regulation 10 mA < IO < 1.5 A 10 mV

PWM switching frequency V

S

Maximum duty cycle V

Switching current limitation

NMOS leakage current V

PMOS leakage current V

-N NMOS switch on resistance I

-P PMOS switch on resistance I

= 0.7 V, TA = 25 °C 1.2 1.5 1.8 MHz

FB

= 0.7 V, TA = 25 °C 85 94 %

FB

(2)

= 0.9 V, TA = 25 °C 0.1 µA

FB

= 0.9 V, TA = 25 °C 0.1 µA

FB

= 250 mA 0.15 0.3 Ω

SW

= 250 mA 0.2 0.4 Ω

SW

= 20 mA to 100 mA 75 %

I

O

I

= 100 mA to 1.5 A 80 %

O

2A

Thermal shutdown 150 °C

Thermal shutdown
hysteresis

Short-circuit VIN range

IN

(2)

Output short-circuit to ground 3 5.3 V

15 °C

%V

V

V3.0 V < V

/

O

IN

6/18 Doc ID 18290 Rev 2