ZXCT1009_05 ZETEX | Alldatasheet

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Technical content

1 SEMICONDUCTORS

DESCRIPTION

The ZXCT1009 is a high side current sense monitor. Using this device eliminates the need to disrupt the ground plane when sensing a load current. It takes a high side voltage developed across a current shunt resistor and translates it into a proportional output current. A user defined output resistor scales the output current into a ground-referenced voltage. The wide input voltage range of 20V down to as low as 2.5V make it suitable for a range of applications. A minimum operating current of just 4/H9262A, combined with its SOT23 package make it a unique solution for portable battery equipment.

FEATURES

  • Low cost, accurate high-side current sensing
  • Output voltage scaling
  • Up to 2.5V sense voltage
  • 2.5V – 20V supply range
  • 4µA quiescent current
  • 1% typical accuracy
  • SOT23 and SM8 packages

APPLICATIONS

  • Battery chargers
  • Smart battery packs
  • DC motor control
  • Over current monitor
  • Power management
  • Level translating
  • Programmable current source ZXCT1009 ISSUE 9 - OCTOBER 2005 HIGH-SIDE CURRENT MONITOR APPLICATION CIRCUIT DEVICE REEL SIZE TAPE WIDTH QUANTITY PER REEL PARTMARKING PACKAGE ZXCT1009FTA 7” 8mm 3,000 units 109 SOT23 ZXCT1009T8TA 7” 12mm 1,000 units ZXCT1009 SM8

ORDERING INFORMATION

Voltage on any pin -0.6V to 20V (relative to I out) Continuous output current 25mA Continuous sense voltage V in + 0.5V > Vsense†> Vin – 5V Operating temperature -40 to 85 °C Storage temperature -55 to 125 °C Package power dissipation (T A = 25°C) SOT23 450mW - derate to zero at 125 °C SM8 2W Operation above the absolute maximum rating may cause device failure. Operation at the absolute maximum ratings for extended periods may reduce device reliability.

ELECTRICAL CHARACTERISTICS

Test Conditions TA = 25°C, Vin = 5V, Rout = 100Ω. SYMBOL PARAMETER CONDITIONS LIMITS UNIT Min Typ Max Vin VCC range 2.5 20 V Iout

1 Output current V sense =0V

Vsense =10mV Vsense =100mV Vsense =200mV Vsense =1V 0.975 1.95 9.6 104 1.002 2.0 9.98 120 1.025 2.05 10.2 µA µA mA mA mA Vsense † Sense voltage 0 2500 mV Isense -V sense - input current 100 nA Acc Accuracy Rsense =0 . 1Ω Vsense =200mV -2.5 2.5 % Gm Transconductance, Iout /V sense 10000 µA/V BW Bandwidth RF P in= -20dBm‡ Vsense = 10mV dc Vsense = 100mV dc 300 kHz MHz

1 Includes input offset voltage contribution†Vsense=Vin-Vload

‡ -20dBm=63mVp-p into 50Ω

100µ 1m 10m 100m 1 10µ 100µ 10m 10m 100m 1 - 4 0 - 2 00 2 04 06 08 0 9.4 9.6 9.8 10.0 10.2 0.01 0.1 1 10 -12 012345 1 10 100 1k 10k 100k 1M 10M -90 -80 -70 -60 -50 -40 -30 -20 -10 VIN =5 V Tamb = 25°C ROUT =0 /c87 Typical Output v Sense Voltage IOUT - Output Current (A) VSENSE (V) Typical VIN =5 V Tamb = 25°C ROUT =0 /c87 Error v Sense Voltage Output Current Error (%) VSENSE (V) VIN =5 V VSENSE =1 V ROUT =0 /c87 Output Current v Temperature IOUT - Output Current (mA) Temperature (°C) VIN =5 V ,T a m b=2 5 ° C ,R FPIN =- 2 0 d B m DC VSENSE =0 . 1 V DC VSENSE =1 V DC VSENSE =0 . 0 1 V Frequency Response Gain (dB) Frequency (MHz) VIN =5 V Tamb = 25°C ROUT =0 /c87 VSENSE =0 . 2 V VSENSE =0 . 4 V VSENSE =0 . 6 V VSENSE =0 . 8 V VSENSE =1 V Transfer Characteristic IOUT - Output Current (mA) VIN - Supply Voltage (V) VIN =5 V Tamb = 25°C RF PIN = -20dBm VSENSE =0 . 0 1 V VSENSE =0 . 1 V VSENSE =1 V Common Mode Rejection Frequency (Hz) Rejection (dB) TYPICAL CHARACTERISTICS

Vsense- Connection to load/battery Iout Output current, proportional to V in-Vload SM8 Package Suffix – T8 Top View SOT23 Package Suffix – F Top View CONNECTION DIAGRAMS SCHEMATIC DIAGRAM TYPICAL CHARACTERISTICS (Cont.)

The following lines describe how to scale a load current to an output voltage. Vsense = Vin -V load Vout = 0.01 x Vsense x Rout1 E.g. A 1A current is to be represented by a 100mV output voltage: 1)Choose the value of R sense to give 50mV > Vsense > 500mV at full load. For example V sense = 100mV at 1.0A. R sense = 2)Choose Rout to give Vout = 100mV, when Vsense = 100mV. Rearranging 1 for Rout gives: Rout =V out /(Vsense x 0.01) Rout = 0.1 / (0.1 x 0.01) = 100 Ω TYPICAL CIRCUIT APPLICATION POWER DISSIPATION The maximum allowable power dissipation of the device for normal operation (Pmax), is a function of the package junction to ambient thermal resistance (θja), maximum junction temperature (Tjmax), and ambient temperature (Tamb), according to the expression: P max = (Tjmax – Tamb) / θja The device power dissipation, P D is given by the expression: PD=Iout.(Vin-Vout) Watts SM8 SOT23 Where Rload represents any load including DC motors, a charging battery or further circuitry that requires monitoring, R sense c a nb es e l e c t e do ns p e c i f i c requirements of accuracy, size and power rating. APPLICATIONS INFORMATION

The above figure shows the ZXCT1009 supporting the Benchmarq bq2954 Charge Management IC. Most of the support components for the bq2954 are omitted for clarity. This design also uses the Zetex FZT789A high current Super-/H9252PNP as the switching transistor in the DC-DC step down converter and the FMMT451 as the drive NPN for the FZT789A. The circuit can be configured to charge up to four Li-Ion cells at a charge current of 1.25A. Charge can be terminated on maximum voltage, selectable minimum current, or maximum time out. Switching frequency of the PWM loop is approximately 120kHz. The ZXCT1009 is intended as a direct functional replacement for the ZDS1009, which is featured in a complete design from Unitrode/Texas Instruments on the Li-Ion charger circuit shown above. Reference: DVS2954S1H Li-Ion Charger Development System. APPLICATIONS INFORMATION (Continued) Transient Protection An additional resistor, Rlim can be added in series with Rout (figure 1.0), to limit the current from Iout. Any circuit connected to Vout will be protected from input voltage transients. This can be of particular use in automotive applications where load dump and other common transients need to be considered. Figure 1.0 ZXCT1009 with additional current limiting Resistor Rlim. Assuming the worst case condition of V out = 0V; providing a low impedance to a transient, the minimum value of R lim is given by:- R( m i n ) VV I lim pk max pk = − Vpk = Peak transient voltage to be withstood Vmax = Maximum working Voltage = 20V Ipk = Peak output current = 40mA The maximum value of R lim is set by V in(min), Vout(max) and the dropout voltage (see transfer characteristic on page 3) of the ZXCT1009 :- R R [V V V (max) V lim out in dp out out (max) (min) ( )] (max) = −+ Vin(min) = MinimumSupply Operating Voltage Vdp =Dropout Voltage Vout (max)= Maximum Operating Output Voltage Charger input MOD pin SNS pin Support components omitted for clarity Iout Vin Load To battery + FMMT3904 FMMT451 ZHCS100 FMMD914 ZXCT1009 FZT789A bq2954

PCB trace shunt resistor for low cost solution The figure below shows output characteristics of the device when using a PCB resistive trace for a low cost solution in replacement for a conventional shunt resistor. The graph shows the linear rise in voltage across the resistor due to the PTC of the material and demonstrates how this rise in resistance value over temperature compensates for the NTC of the device. The figure opposite shows a PCB layout suggestion. The resistor section is 25mm x 0.25mm giving approximately 150mΩ using 1oz copper. The data for the normalised graph was obtained using a 1A load current and a 100 Ω output resistor. An electronic version of the PCB layout is available at www.zetex.com/isense. -40 -20 0 20 40 60 80 100 120 140 0.8 1.0 1.2 1.4 Effect of Sense Resistor Material on Temperature Performance VOUT with Ideal Sense Resistor VOUT with Copper Sense Resistor Voltage across Copper Sense Resistor Normalised Voltage Temperature (°C) APPLICATIONS INFORMATION (Continued) Layout shows area of shunt resistor compared to SOT23 package. Not actual size Actual Size Vout Vin GND Load tuoR ZXCT1009 Vout Vin GND Load tuoR ZXCT1009

Streitfeldstraße 19 D-81673 München Germany Telefon: (49) 89 45 49 49 0 Fax: (49) 89 45 49 49 49 europe.sales@zetex.com Americas Zetex Inc

700 Veterans Memorial Hwy

Hauppauge, NY 11788 USA Telephone: (1) 631 360 2222 Fax: (1) 631 360 8222 usa.sales@zetex.com Asia Pacific Zetex (Asia) Ltd 3701-04 Metroplaza Tower 1 Hing Fong Road, Kwai Fong Hong Kong Telephone: (852) 26100 611 Fax: (852) 24250 494 asia.sales@zetex.com Corporate Headquarters Zetex Semiconductors plc Zetex Technology Park Chadderton, Oldham, OL9 9LL United Kingdom Telephone (44) 161 622 4444 Fax: (44) 161 622 4446 hq@zetex.com These offices are supported by agents and distributors in major countries world-wide. This publication is issued to provide outline information only which (unless agreed by the Company in writing) may not be used, applied or reproduced for any purpose or form part of any order or contract or be regarded as a representation relating to the products or services concerned. The Company reserves the right to alter without notice the specification, design, price or conditions of supply of any product or service. For the latest product information, log on to www.zetex.com © Zetex Semiconductors plc 2005 N PACKAGE DIMENSIONS SOT23 DIM Millimeters Inches M i nM a xM i nM a x A 2.67 3.05 0.105 0.120 B 1.20 1.40 0.047 0.055 C – 1.10 – 0.043 D 0.37 0.53 0.0145 0.021 F 0.085 0.15 0.0033 0.0059 G NOM 1.9 NOM 0.075 K 0.01 0.10 0.0004 0.004 L 2.10 2.50 0.0825 0. 0985 N NOM 0.95 NOM 0.037 DIM Millimeters Inches Min Typ Max Min Typ Max A1 0.02 – 0.1 0.0008 – 0.004 c 0.24 – 0.32 0.009 – 0.013 D 6.3 – 6.7 0.248 – 0.264 E 3.3 – 3.7 0.130 – 0.145 He 6.7 – 7.3 0.264 – 0.287 β – 10° – – 10° – PACKAGE DIMENSIONS SM8