L6738ATR STMicroelectronics, L6738ATR Datasheet
L6738ATR
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L6738ATR Summary of contents
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Features ■ Flexible power supply from bus ■ Power conversion input as low as 1.5 V ■ Light-load efficiency optimization ■ Embedded bootstrap diode ■ VIN detector ■ 0.8 V internal reference ■ 0.5 % ...
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Contents Contents 1 Typical application circuit and block diagram . . . . . . . . . . . . . . . . . . . . 5 1.1 Application circuit . . . . . . . ...
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L6738A 10.3 Input capacitors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...
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List of tables List of tables Table 1. Device summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...
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L6738A List of figures Figure 1. Typical application circuit (fast protections ...
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Typical application circuit and block diagram 1 Typical application circuit and block diagram 1.1 Application circuit Figure 1. Typical application circuit (fast protections 12V CC R OSC OSC PGOOD PGOOD EN EN COMP ...
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L6738A Figure 2. Typical application circuit 12V CC R OSC OSC PGOOD PGOOD EN EN COMP FBG I L6738A Reference Schematic Typical ...
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Typical application circuit and block diagram 1.2 Block diagram Figure 3. Block diagram OVER CURRENT CSN CSP OCP CLOCK OSC PROGRAMMABLE OSCILLATOR EN OVP +25% UVP -25% 8/32 OVP UVP CONTROL LOGIC, MONITOR, PROTECTIONS & EFFICIENCY OPTIMIZATION PWM ERROR AMPLIFIER ...
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L6738A 2 Pin description and connection diagrams Figure 4. Pin connection (top view) 2.1 Pin descriptions Table 2. Pin description Pin# Name Low side driver section power supply. 1 VCCDR Operative voltage bus. Filter ...
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Pin description and connection diagrams Table 2. Pin description (continued) Pin# Name Error amplifier output. 8 COMP Connect with an R Error amplifier inverting input Connect with a resistor R Output voltage monitor. 10 VSEN It manages OVP ...
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L6738A 3 Electrical specifications 3.1 Absolute maximum ratings Table 4. Absolute maximum ratings Symbol GND CC, CCDR to GND PHASE BOOT UGATE to GND, VCCDR = < 200 nsec. to ...
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Electrical specifications Table 5. Electrical characteristics (continued) Symbol Parameter ∆V PWM ramp amplitude OSC d Duty cycle Input logic high EN Input logic low Reference and error amplifier Output voltage accuracy ( gain 0 GBWP Gain-bandwidth product (1) ...
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L6738A 4 Device description and operation The L6738A is a single-phase PWM controller with embedded high-current drivers that provides complete control logic and protections to realize a general DC-DC step-down converter. Designed to drive N-channel MOSFETs in a synchronous buck ...
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Soft-start 5 Soft-start The L6738A implements a soft-start to smoothly charge the output filter avoiding high in- rush currents to be required to the input power supply. During this phase, the device increases the internal reference from zero up to ...
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L6738A Figure 5. LS-less startup (left) vs. non-LS-less startup (right) Doc ID 18134 Rev 1 Soft-start 15/32 ...
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Output voltage setting and protections 6 Output voltage setting and protections The L6738A is capable of precisely regulating an output voltage as low as 0 fact, the device comes with a fixed 0.8 V internal reference that guarantees ...
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L6738A For proper operations, VCC needs least 1.5 V higher than the programmed output voltage. Table 6. L6738A Protection at a glance. L6738A Overvoltage (OV) Undervoltage (UV) PGOOD Overcurrent (OC) 6.1 Overcurrent The overcurrent function protects the ...
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Output voltage setting and protections 6.2 Overcurrent threshold setting The L6738A detects OC when the difference between CSP and CSN is equal (typ). By properly designing the current reading network possible to program the OC ...
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L6738A 7 Main oscillator The controller embeds a programmable oscillator. The internal oscillator generates the sawtooth waveform for the PWM charging with a constant current and resetting an internal capacitor. The switching frequency, F The current delivered to the oscillator ...
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High Current embedded drivers 8 High Current embedded drivers The L6738A provides high-current driving control. The driver for the high-side MOSFET uses the BOOT pin for supply and the PHASE pin for return. The driver for the low-side MOSFET uses ...
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L6738A Two main terms contribute in the device power dissipation: bias power and drivers' power. ● Device Power (P supply pins and it is simply quantifiable as follows: ● Drivers' power is the power needed by the driver to continuously ...
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Application details 9 Application details 9.1 Compensation network The control loop shown in regulated to the internal reference (when present, an offset resistor between FB node and GND can be neglected in control loop calculation). Error amplifier output is compared ...
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L6738A Figure 10. Example of type III compensation. Gain [dB] open loop EA gain closed loop gain compensation gain open loop converter gain 0dB ● Open loop converter singularities ESR ● Compensation Network ...
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Application details a) Set the gain R according to the approximated formula (suggested values for R of some kΩ): R F ---------- = Place F = ---------------------------------- - C F π c) Place F = ------------------------------------------------------------------ - ...
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L6738A Connect output bulk capacitors (C inductance and resistance associated to the copper trace, also adding extra decoupling capacitors along the way to the load when this results in being far from the bulk capacitors bank. Remote Sense Connection must ...
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Application information 10 Application information 10.1 Inductor design The inductance value is defined by a compromise between the dynamic response time, the efficiency, the cost, and the size. The inductor must be calculated to maintain the ripple current (∆I ) ...
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L6738A 10.2 Output capacitor(s) The output capacitors are basic components to define the ripple voltage across the output and for the fast transient response of the power supply. They depend on the output voltage ripple requirements, as well as any ...
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Application information therefore in higher ripple voltages. For these reasons, a mix between electrolytic and MLCC capacitors is suggested to minimize ripple as well as reduce voltage deviation in dynamic mode. 10.3 Input capacitors The input capacitor bank is designed ...
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L6738A 11 Package mechanical data 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. ...
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Package mechanical data Figure 14. VFQFPN16 mechanical data and package dimensions DIM. MIN 0. 0.45 L 0.30 ddd 30/32 mm mils TYP. MAX. MIN. TYP. ...
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L6738A 12 Revision history Table 7. Document revision history Date 03-Nov-2010 Revision 1 Initial release. Doc ID 18134 Rev 1 Revision history Changes 31/32 ...
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