ST B5973D User Manual

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Features

■ Qualified following the AEC-Q100

requirements (temperature Grade 1), see PPAP for more details.

■ 2 A DC output current

■ Operating input voltage from 4 V to 36 V

■ 3.3 V / (±2 %) reference voltage

■ Output voltage adjustable from 1.235 V to 35 V

■ Low dropout operation: 100 % duty cycle

■ 250 kHz internally fixed frequency

■ Voltage feedforward

■ Zero load current operation

■ Internal current limiting

■ Inhibit for zero current consumption

■ Synchronization

■ Protection against feedback disconnection

■ Thermal shutdown

Applications

■ Dedicated to automotive applications

Figure 1. Typical application

VIN=4V to 35V

10uF

35V

CERAMIC

220pF

22nF

VCC

COMP

4k7

VREF

3.3V

A5973D

GND

B5973D

2 A step down switching regulator

for automotive applications

HSOP8 exposed pad

Description

The B5973D is a step down monolithic power switching regulator with a minimum switch current limit of 2.25 A so it is able to deliver up to 2 A DC current to the load depending on the application conditions. The output voltage can be set from

1.235 V to 35 V. The high current level is also achieved thanks to an SO8 package with exposed frame, that allows to reduce the R approximately 40 °C/W. The device uses an internal P-channel DMOS transistor (with a typical R

of 250 mΩ) as switching element to

DSon

minimize the size of the external components. An internal oscillator fixes the switching frequency at 250 kHz. Having a minimum input voltage of 4V only, it is particularly suitable for 5 V bus. Pulse by pulse current limit with the internal frequency modulation offers an effective constant current short circuit protection. Pulse by pulse current limit with the internal frequency modulation offers an effective constant current short circuit protection.

L1 15uH

OUT

SYNCH

INH

STPS340U

5k6

3k3

th(JA)

down to

Vout=3.3V

330uF

6.3V

August 2008 Rev 3 1/11

www.st.com

B5973D Contents

Contents

1 Pin settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

1.1 Pin connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

1.2 Pin description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

2 Electrical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

2.1 Maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

2.2 Thermal data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

3 Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

4 Typical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

5 Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

6 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

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B5973D

1 Pin settings

1.1 Pin connection

Figure 2. Pin connection (top view)

1.2 Pin description

Table 1. Pin description

N° Pin Description

1 OUT Regulator output.

2 SYNCH Master/slave synchronization.

A logical signal (active high) disables the device. If INH not used the pin

3INH

4 COMP E/A output for frequency compensation.

5FB

6 VREF 3.3 V V

7 GND Ground.

8 VCC Unregulated DC input voltage.

must be grounded. When it is open an internal pull-up disable the device.

Feedback input. Connecting directly to this pin results in an output voltage of 1.23 V. An extenal resistive divider is required for higher output voltages.

REF. No cap is requested for stability.

2/11

Electrical data B5973D

2 Electrical data

2.1 Maximum ratings

Table 2. Absolute maximum ratings

Symbol Parameter Value Unit

, V

TOT

STG

Input voltage 40 V

OUT pin DC voltage OUT pin peak voltage at Δt = 0.1μs

Maximum output current int. limit.

Analog pins 4 V

INH -0.3 to V

SYNCH -0.3 to 4 V

Power dissipation at TA ≤ 70 °C 2.25 W

Operating junction temperature range -40 to 150 °C

Storage temperature range -55 to 150 °C

2.2 Thermal data

Table 3. Thermal data

Symbol Parameter SO8 Unit

thJA Maximum thermal resistance junction-ambient 40

1. Package mounted on board

-1 to 40

-5 to 40

(1)

V V

°C/W

3/11

B5973D

3 Electrical characteristics

Table 4. Electrical characteristics

= -40 °C to 125 °C, V

Symbol Parameter Test condition Min Typ Max Unit

= 12 V, unless otherwise specified)

DS(on)

Operating input voltage range

MOSFET on resistance

Maximum limiting current

(1)

Switching frequency 212 250 280 kHz

= 1.235 V; I0 = 2 A 4 36 V

= 5 V, TJ = 25 °C 2.5 3 3.5

Duty cycle 0 100 %

Dynamic characteristics (see test circuit).

Voltage feedback

η Efficiency V

4.4 V < V 20 mA < I0 < 2 A

= 5 V, V

DC characteristics

qop

qst-by

Total operating quiescent current

Quiescent current Duty cycle = 0; V

Total stand-by quiescent current

V V

> 2.2 V 50 100 μA

inh

> 2.2 V

inh

Inhibit

Device ON 0.8 V

INH threshold voltage

Device OFF 2.2 V

0.250 0.5 Ω

= 5 V 2.25 3 3.5

< 36 V,

= 12 V 90 %

1.198 1.235 1.272 V

35mA

= 1.5 V 2.5 mA

= 36 V;

80 150 μA

Error amplifier

Io source

o sink Sink output current

High level output voltage

Low level output

voltage

Source output current

b Source bias current 2.5 4 μA

DC open loop gain R

= 1 V 3.5 V

= 1.5 V 0.4 V

= 1.9 V; VFB = 1 V

COMP

= 1.9 V; V

COMP

L = ∞ 50 65 dB

= 1.5 V

190 300 μA

11.5 mA

4/11

Electrical characteristics B5973D

Table 4. Electrical characteristics

= -40 °C to 125 °C, V

Symbol Parameter Test condition Min Typ Max Unit

gm Transconductance

Synch function

= 12 V, unless otherwise specified)

= -0.1 mA to 0.1 mA;

COMP

= 1.9 V

COMP

2.3 mS

High input voltage

Low input voltage

Slave synch current

Master output amplitude

Output pulse width

Reference section

Reference voltage

Line regulation

Load regulation

Short circuit current 5 18 35 mA

1. With TJ = 85 °C, I

2. Guarantee by design

lim_min

= 4.4 to 36 V;

synch

(2)

= 1.65 V

= 0.74 V

synch

= 2.33 V

synch

= 3 mA

source

no load, V

= 0 to 5 mA

REF

= 4.4 V to 36 V

= 0 mA

REF

= 4.4 V to 36 V

= 0 mA

REF

= 2.5 A, assured by design, characterization and statistical correlation.

2.5 V

0.11

0.21

2.75 3 V

0.20 0.35 μs

3.2 3.3 3.399 V

510mV

815mV

REF

0.74 V

0.25

0.45

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B5973D

4 Typical characteristics

Figure 3. Line regulation Figure 4. Shutdown current vs

junction temperature

Figure 5. Output voltage vs junction

temperature

Figure 7. Quiescent current vs

junction temperature

Figure 6. Switching frequency vs

junction temperature

6/11

Typical characteristics B5973D

Figure 8. Junction temperature vs

Figure 10. Efficiency vs output current Figure 11. Efficiency vs output current

output current

Figure 9. Junction temperature vs

output current

7/11

B5973D

5 Package mechanical data

In order to meet environmental requirements, ST offers these devices in ECOPACK® packages. These packages have a lead-free second level interconnect. The category of second level interconnect is marked on the package and on the inner box label, in compliance with JEDEC Standard JESD97. The maximum ratings related to soldering conditions are also marked on the inner box label. ECOPACK is an ST trademark. ECOPACK specifications are available at: www.st.com

8/11

Package mechanical data B5973D

Table 5. HSOP8 mechanical data

mm inch

Dim

Min Typ Max Min Typ Max

A 1.70 0.0669

A1 0.00 0.10 0.00 0.0039

A2 1.25 0.0492

b 0.31 0.51 0.0122 0.0201

c 0.17 0.25 0.0067 0.0098

D 4.80 4.90 5.00 0.1890 0.1929 0.1969

D1 3 3.1 3.2 0.118 0.122 0.126

E 5.80 6.00 6.20 0.2283 0.2441

E1 3.80 3.90 4.00 0.1496 0.1575

E2 2.31 2.41 2.51 0.091 0.095 0.099

e1.27

h 0.25 0.50 0.0098 0.0197

L 0.40 1.27 0.0157 0.0500

k0° (min), 8° (max)

ccc 0.10 0.0039

Figure 12. Package dimensions

9/11

B5973D

6 Revision history

Table 6. Document revision history

Date Revision Changes

07-Nov-2007 1 Initial release

14-Jan-2008 2 Updated Table 5 on page 9

27-Aug-2008 3 Updated: Coverpage and Table 4 on page 4

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B5973D

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11/11

ST B5973D User Manual

Specifications and Main Features

Frequently Asked Questions

User Manual

Figure 1. Typical application

1 Pin settings

1.1 Pin connection

Figure 2. Pin connection (top view)

1.2 Pin description

Table 1. Pin description

2 Electrical data

2.1 Maximum ratings

Table 2. Absolute maximum ratings

2.2 Thermal data

Table 3. Thermal data

3 Electrical characteristics

4 Typical characteristics

Figure 10. Efficiency vs output current Figure 11. Efficiency vs output current

5 Package mechanical data

Table 5. HSOP8 mechanical data

Figure 12. Package dimensions

6 Revision history

Table 6. Document revision history