Datasheet

ManualsBrandsSTMICROELECTRONICS ManualsPMICsPMIC - DC/DC voltage regulator Holder HSOP 8

This is information on a product in full production.

December 2013 DocID14117 Rev 4 1/44

B5973D

2 A step down switching regulator for automotive applications

Datasheet - production data

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

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 HSOP8 package (i.e. SO8

package with exposed frame), that allows to

reduce the R

th(JA)

down to approximately 40

°C/W. The device uses an internal P-channel

DMOS transistor (with a typical R

DSon

of 250 m)

as switching element to minimize the size of the

external components. An internal oscillator fixes

the switching frequency at 250 kHz. Having a

minimum input voltage of 4 V 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.

HSOP8 - exposed pad

Figure 1. Typical application



95()



9&&

6<1&



&203







287





,1+

*1'

%'

9,1 9 WR 9

9287  9

&

)

9

&(5$0,&

&

Q)

5

&

S)

5

5

/ +

'

67368

&

)

9

$0

www.st.com

Summary of content (44 pages)

PAGE 1
B5973D 2 A step down switching regulator for automotive applications Datasheet - production data  Protection against feedback disconnection  Thermal shutdown Applications HSOP8 - exposed pad  Dedicated to automotive applications Description Features 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.
PAGE 2
Contents B5973D Contents 1 2 Pin settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 1.1 Pin connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 1.2 Pin description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Electrical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 2.1 Maximum ratings . . .
PAGE 3
B5973D 8 Contents Application information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 8.1 Component selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 Input capacitor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 Output capacitor. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 Inductor . . . . . . . . . . . . . . .
PAGE 4
Pin settings B5973D 1 Pin settings 1.1 Pin connection Figure 2. Pin connection (top view) 287 9&& 6<1& *1' ,1+ 95() &203 )% $0 1.2 Pin description Table 1. Pin description 4/44 N° Pin Description 1 OUT 2 SYNCH 3 INH 4 COMP 5 FB 6 VREF 3.3 V VREF. No cap. is requested for stability. 7 GND Ground. 8 VCC Unregulated DC input voltage. Regulator output. Master/slave synchronization. A logical signal (active high) disables the device.
PAGE 5
B5973D Electrical data 2 Electrical data 2.1 Maximum ratings Table 2. Absolute maximum ratings Symbol Value Unit 40 V V V V8 Input voltage V1 OUT pin DC voltage OUT pin peak voltage at t = 0.1 s -1 to 40 -5 to 40 I1 Maximum output current Int. limit. V4 , V5 Analog pins 4 V -0.3 to VCC V -0.3 to 4 V 2.
PAGE 6
Electrical characteristics 3 B5973D Electrical characteristics Table 4. Electrical characteristics (TJ = -40 °C to 125 °C, VCC = 12 V, unless otherwise specified) Symbol VCC RDS(on) IL fSW Parameter Test condition Operating input voltage range V0 = 1.235 V; I0 = 2 A Min. Max. Unit 36 V 0.250 0.5  4 MOSFET on resistance Maximum limiting current(1) Typ. VCC = 5 V 2.25 3 3.5 VCC = 5 V, TJ = 25 °C 2.5 3 3.5 212 250 280 kHz 100 % 1.
PAGE 7
B5973D Electrical characteristics Table 4. Electrical characteristics (TJ = -40 °C to 125 °C, VCC = 12 V, unless otherwise specified) (continued) Symbol gm Parameter Transconductance Test condition Min. ICOMP = -0.1 mA to 0.1 mA; VCOMP = 1.9 V Typ. Max. 2.3 Unit mS Synch function High input voltage VCC = 4.4 to 36 V Low input voltage VCC = 4.4 to 36 V Slave synch current Vsynch = 0.74 V (2) Vsynch = 2.33 V 2.5 0.11 0.21 VREF V 0.74 V 0.25 0.
PAGE 8
Datasheet parameters over the temperature range 4 B5973D Datasheet parameters over the temperature range The 100% of the population in the production flow is tested at three different ambient temperatures (-40 C; +25 C, +125 C) to guarantee the datasheet parameters inside the junction temperature range (-40 C; +125 C). The device operation is so guaranteed when the junction temperature is inside the (-40 C; +150 C) temperature range.
PAGE 9
B5973D 5 Functional description Functional description The main internal blocks are shown in the device block diagram in Figure 3. They are:  A voltage regulator supplying the internal circuitry. From this regulator, a 3.3 V reference voltage is externally available.  A voltage monitor circuit which checks the input and the internal voltages.
PAGE 10
Functional description 5.1 B5973D Power supply and voltage reference The internal regulator circuit (shown in Figure 4) consists of a startup circuit, an internal voltage pre-regulator, the Bandgap voltage reference and the Bias block that provides current to all the blocks. The Starter supplies the startup currents to the entire device when the input voltage goes high and the device is enabled (inhibit pin connected to ground).
PAGE 11
B5973D Functional description The synchronization feature of a set of the B5973D is simply get connecting together their SYNC pin. The device with highest switching frequency will be the MASTER and it provides the synchronization signal to the others. Therefore the SYNC is an I/O pin to deliver or recognize a frequency signal.
PAGE 12
Functional description B5973D Figure 6. Synchronization example 6<1& 9&& 95() &203 6<1& 9&& 95() &203 % ' 6<1& )% 9&& 95() &203 ,1+ *1' 287 % ' 6<1& 287 9&& )% 95() &203 ,1+ *1' % ' ,1+ *1' % ' 287 )% 287 )% ,1+ *1' $0 5.4 Current protection The B5973D features two types of current limit protection: pulse-by-pulse and frequency foldback.
PAGE 13
B5973D Functional description Figure 7. Current limitation circuitry 9&& 56(16( $ 57+ $ ,/ '5,9(5 127 $ $ 287 , , 3:0 $0 5.5 Error amplifier The voltage error amplifier is the core of the loop regulation. It is a transconductance operational amplifier whose non inverting input is connected to the internal voltage reference (1.235 V), while the inverting input (FB) is connected to the external divider or directly to the output voltage.
PAGE 14
Functional description B5973D time of the current at turn ON, is a very critical parameter. At a first approach, it appears that the faster the rise time, the lower the turn ON losses. However, there is a limit introduced by the recovery time of the recirculation diode. In fact, when the current of the power element is equal to the inductor current, the diode turns OFF and the drain of the power is able to go high.
PAGE 15
B5973D 5.7 Functional description Inhibit function The inhibit feature is used to put the device in standby mode. With the INH pin higher than 2.2 V the device is disabled and the power consumption is reduced to less than 100 µA. With the INH pin lower than 0.8 V, the device is enabled. If the INH pin is left floating, an internal pull up ensures that the voltage at the pin reaches the inhibit threshold and the device is disabled. The pin is also Vcc compatible. 5.
PAGE 16
Additional features and protection B5973D 6 Additional features and protection 6.1 Feedback disconnection If the feedback is disconnected, the duty cycle increases towards the maximum allowed value, bringing the output voltage close to the input supply. This condition could destroy the load. To avoid this hazardous condition, the device is turned OFF if the feedback pin is left floating. 6.
PAGE 17
B5973D Closing the loop Figure 9.
PAGE 18
Closing the loop 7.1 B5973D Error amplifier and compensation network The output L-C filter of a step-down converter contributes with 180 degrees phase shift in the control loop. For this reason a compensation network between the COMP pin and GROUND is added. The simplest compensation network together with the equivalent circuit of the error amplifier are shown in Figure 10. RC and CC introduce a pole and a zero in the open loop gain.
PAGE 19
B5973D Closing the loop The poles of this transfer function are (if Cc >> C0+CP): Equation 3 1 F P1 = ------------------------------------2    R0  Cc Equation 4 1 F P2 = -------------------------------------------------------2    Rc   C0 + Cp  whereas the zero is defined as: Equation 5 1 F Z1 = ------------------------------------2    Rc  Cc FP1 is the low frequency which sets the bandwidth, while the zero FZ1 is usually put near to the frequency of the double pole of the L-C filter (see S
PAGE 20
Closing the loop B5973D The poles of the transfer function can be calculated through the following expression: Equation 9 2 – ESR  C OUT   ESR  C OUT  – 4  L  C OUT F PLC1 2 = -----------------------------------------------------------------------------------------------------------------------------------------2  L  C OUT In the denominator of ALC the typical second order system equation can be recognized: Equation 10 2 s + 2    n  s +  2 n If the damping coefficient  is very close
PAGE 21
B5973D Closing the loop In summary, the open loop gain can be expressed as: Equation 15 R2 G  s  = G PWM  s   --------------------  A O  s   A LC  s  R1 + R2 Example: Considering RC = 2.7 k, CC = 22 nF and CP = 220 pF, the poles and zeroes of A0 are: FP1 = 9 Hz FP2 = 256 kHz FZ1 = 2.68 kHz If L = 22 µH, COUT = 100 µF and ESR = 80 m, the poles and zeroes of ALC become: FPLC = 3.39 kHz F0 = 19.89 kHz Finally R1 = 5.6 k and R2 = 3.3 k.
PAGE 22
Closing the loop B5973D Figure 12. Phase plot The cut-off frequency and the phase margin are: Equation 16 F C = 22.8KHz Phase margin = 39.
PAGE 23
B5973D Application information 8 Application information 8.1 Component selection Input capacitor The input capacitor must be able to support the maximum input operating voltage and the maximum RMS input current. Since step-down converters draw current from the input in pulses, the input current is squared and the height of each pulse is equal to the output current.
PAGE 24
Application information B5973D Capacitors that can be considered are: Electrolytic capacitors These are widely used due to their low price and their availability in a wide range of RMS current ratings. The only drawback is that, considering ripple current rating requirements, they are physically larger than other capacitors.
PAGE 25
B5973D Application information Table 7. Output capacitor selection Manufacturer Series Cap. value (µF) Rated voltage (V) ESR (m) Sanyo POSCAP(1) TAE 100 to 470 4 to 16 25 to 35 THB/C/E 100 to 470 4 to 16 25 to 55 AVX TPS 100 to 470 4 to 35 50 to 200 KEMET T494/5 100 to 470 4 to 20 30 to 200 Sprague 595D 220 to 390 4 to 20 160 to 650 1. POSCAP capacitors have some characteristics which are very similar to tantalum.
PAGE 26
Application information 8.2 B5973D Layout considerations The layout of switching DC-DC converters is very important to minimize noise and interference. Power-generating portions of the layout are the main cause of noise and so high switching current loop areas should be kept as small as possible and lead lengths as short as possible. High impedance paths (in particular the feedback connections) are susceptible to interference, so they should be as far as possible from the high current paths.
PAGE 27
B5973D Application information compensate for the losses in the overall application. For this reason, the switching losses related to the RDSON increases compared to an ideal case.  Switching losses due to turning ON and OFF.
PAGE 28
Application information B5973D Example:  VIN = 12 V  VOUT = 3.3 V  IOUT = 2 A RDS(on) has a typical value of 0.25 at 25 °C and increases up to a maximum value of 0.5  at 150 °C. We can consider a value of 0.4 . TSW is approximately 70 ns. IQ has a typical value of 2.5 mA at VIN = 12 V. The overall losses are: Equation 25 2 P TOT = R DSON   I OUT   D + V IN  I OUT  T SW  F SW + V IN  I Q = 2 = 0.4  2  0.3 + 12  2  70  10 –9  250  10 –3 + 12  2.5  10 –3  0.
PAGE 29
B5973D Application information Equation 29 –  V D + V out + DCR L  I  I L TOFF = ---------------------------------------------------------------  T OFF  L where VD is the voltage drop across the diode, DCRL is the series resistance of the inductor.
PAGE 30
Application information B5973D Figure 15. Short-circuit current VIN = 12 V Figure 16.
PAGE 31
B5973D Application information Figure 17. Short-circuit current VIN = 36 V 8.5 Application circuit Figure 18 shows the evaluation board application circuit, where the input supply voltage, VCC, can range from 4 V to 36 V and the output voltage is adjustable from 1.235 V to 6.3 V due to the voltage rating of the output capacitor,. Figure 18.
PAGE 32
Application information B5973D Table 9. Component list Reference Part number Description Manufacturer C1 GCM32ER71H475K 4.7 µF, 50 V Murata C2 POSCAP 6TAE330ML 330 µF, 6.3 V Sanyo C3 C1206C221J5GAC 47 pF, 5%, 50 V KEMET C4 C1206C223K5RAC 22 nF, 10%, 50 V KEMET R1 5.6 k, 1%, 0.1 W 0603 Neohm R2 3.3 k, 1%, 0.1 W 0603 Neohm R3 22 k, 1%, 0.1 W 0603 Neohm D1 STPS3L40U 2 A, 40 V STMicroelectronics L1 DO3316T-153MLD 15 µH, 3.1 A Coilcraft Figure 19.
PAGE 33
B5973D Application information Figure 20. PCB layout (bottom side) Figure 21.
PAGE 34
Application information 8.6 B5973D Positive buck-boost regulator The device can be used to implement a step-up/down converter with a positive output voltage. The output voltage is given by: Equation 32 D V OUT = V IN  ------------1–D where the ideal duty cycle D for the buck boost converter is: Equation 33 V OUT D = -----------------------------V IN + V OUT However, due to power losses in the passive elements, the real duty cycle is always higher than this.
PAGE 35
B5973D Application information Figure 22. Positive buck-boost regulator ' 6736 / / + 95() 9,1 9 9&& 6<1& &203 & ) 9 &(5$0,& & Q) & S) % ' ,1+ 287 )% 9287 9 $ 5 ' 6736 / *1' 0 671 1) / 5 5 & ) 9 (65 ! P $0 8.7 Negative buck-boost regulator In Figure 23, the schematic circuit for a standard buck-boost topology is shown.
PAGE 36
Application information B5973D Figure 23.
PAGE 37
B5973D 8.8 Application information Synchronization example See Section 5.3: Oscillator and synchronization on page 10 for details. Figure 24. Synchronization example 9,1 9&& ) 9 &(5$0,& &203 95() 6<1& Q) &(5$0,& % ' 287 )% 9&& &203 95() 6<1& ,1+ *1' Q) &(5$0,& % ' ,1+ 287 )% *1' $0 8.
PAGE 38
Application information B5973D Figure 25 shows an example of a compensation network stabilizing the system with ceramic capacitors at the output (the optimum component value depends on the application). Figure 25. MLCC compensation network example / + 95() 9,1 9 9&& 6<1& & ) 9 &(5$0,& &203 & S) & S) & Q) % ' ,1+ 9287 287 )% ' 6736 / 8 5 *1' 9 & Q) 5 & 0/&& ) 9 5 5 $0 8.
PAGE 39
B5973D 9 Typical characteristics Typical characteristics Figure 27. Line regulation Figure 28. Shutdown current vs. junction temperature Figure 29. Output voltage vs. junction temperature Figure 30. Switching frequency vs. junction temperature Figure 31. Quiescent current vs.
PAGE 40
Typical characteristics 40/44 B5973D Figure 32. Junction temperature vs. output current Figure 33. Junction temperature vs. output current Figure 34. Efficiency vs. output current Figure 35. Efficiency vs.
PAGE 41
B5973D 10 Package information Package information In order to meet environmental requirements, ST offers these devices in different grades of ECOPACK® packages, depending on their level of environmental compliance. ECOPACK specifications, grade definitions and product status are available at: www.st.com. ECOPACK is an ST trademark.
PAGE 42
Package information B5973D Figure 36. HSOP8 package outline Table 10. HSOP8 package mechanical data Dimensions Symbol mm Min. Typ. A Max. Min. Typ. 1.70 Max. 0.0669 A1 0.00 A2 1.25 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 e 0.10 0.00 0.0039 0.0492 0.095 0.099 1.27 h 0.25 0.
PAGE 43
B5973D 11 Ordering information Ordering information Table 11. Order codes Order code Package B5973D Tube HSOP8 B5973DTR 12 Packaging Tape and reel Revision history Table 12. Document revision history Date Revision 07-Nov-2007 1 Initial release 14-Jan-2008 2 Updated Table 10 on page 42 27-Aug-2008 3 Updated: Coverpage and Table 4 on page 6 4 Added Section 4: Datasheet parameters over the temperature range on page 8 to Section 8: Application information on page 23.
PAGE 44
B5973D Please Read Carefully: Information in this document is provided solely in connection with ST products. STMicroelectronics NV and its subsidiaries (“ST”) reserve the right to make changes, corrections, modifications or improvements, to this document, and the products and services described herein at any time, without notice. All ST products are sold pursuant to ST’s terms and conditions of sale.