Functional application

High -efficiency multi -gain architecture: Peak DSP power supply efficiency gt; 85%baseband power supply output voltage pair:

1.2V/1.5V and mobile phone and paging machine 1.2V /1.575v [123: 123] Portable electronic equipment

Dynamic output voltage selection

± 3%output voltage accuracy description

output current as high as 250mA LM2770 is the switching capacitor drop Voltage

It is suitable for a regulator for power supply for low voltage 2.7V to 5.5V in the portable system. LM2770 can be

The dormant current supply load current of the low power supply current is as high as 250 mAh, and at the 55μA full power static power supply current, the input voltage range is 2.7V to 5.5V. This makes the mode LM2770 from a single battery lithium -ion battery and charger. The output soft startup voltage of the LM2770 can be dynamically switched

The full power mode of the two output levels with logical input pins is protected.

The currently available dormant mode output voltage pair of flow limit protection includes

1.2V/1.5V and 1.2V/1.575V. Other voltage WSON-10 packaging (3mm × 3mm × 0.8mm) can develop options as required.

Explanation (continued)

LM2770's efficiency is better than fixed gain switching capacitance voltage voltage regulator and low -voltage differential stabilizer (LDO To. Multiple score gains enable the entire input voltage and output power efficiency to maximize the current range. When the load current is light (≤20mA). In the dormant mode, the charge pump is turned off, and the output is low -no -noise and low -power linear driving regulator. It also includes soft launch, short -circuit protection, current limit protection and heat shutdown protection. This LM2770 is provided in a small 10-pin leading-free lead frame component (WSON-10) of TI.

Absolute maximum rated value (1) (2) (3)

(1) Absolute maximum rated value The limit value of the component may cause damage. Rate the rated value refers to which operation specifies the device. The operating rated value does not mean specified performance restrictions. For the specified performance restrictions and related test conditions, see the electrical characteristic table.

(2) All voltage is related to the potential of the GND pin.

(3) If you need military/aerospace special equipment, please contact the Texas Instrument Sales Office/dealer to obtain standardization.

(4) Internal heat shutdown circuit protection equipment exempts permanentnessdamage. The heat stop is intermittently open at TJ u003d 150OC (typical) and at TJ u003d 140OC (typical values).

(5) Short -circuit protection circuit may not be affected by direct destructive faults when VOUT is short -circuited on the ground. Application of continuous GND on the output short circuit may shorten the life of the device.

(6) For more information on welding requirements and suggestions, please refer to the application instructions of Texas Instrument Company 1187

(Literature Number: SNOA401): Lead -free lead frame component (LLP (LLP To.

(7) The human model is a 100pf capacitor, which is transplanted to each pin through 1.5K The machine model is 200PF capacitor discharged directly to each pin. MIL-SDD-883 3015.7

(1) Absolute maximum rated value indicates the limit of damage to the component. Rate the rated value refers to which operation specifies the device. The operating rated value does not mean specified performance restrictions. For the specified performance restrictions and related test conditions, see the electrical characteristic table.

(2) All voltage is related to the potential of the GND pin.

(3) The highest environmental temperature (TA-MAX) depends on the maximum power consumption (PD-MAX) of the device in the application The thermal resistance of the environment is in the application (θJa), as shown in the following formula: TA-MAX u003d TJ-MAX-op-(θJa × PD-MAX).

Electrical characteristics (1) (2)

The limit value in the standard font is tj u003d 25OC. The limitation of the black body type is suitable for the entire operating knot temperature range (-30 ° C ≤TJ ≤+105 ° C). Unless otherwise explained, the specifications are applicable to the typical application circuit of LM2770 (page 1), and the content is as follows: vin u003d 3.6V; v (en) u003d vSEL u003d 1.8V, V (sleep) u003d 0V, CIN u003d COUT u003d 10 μF, C1 u003d c2 u003d 1.0μF. (3)

(1) All voltage are related to the potential of the GND pin.

(2) The minimum and maximum limit is specified by design, testing or statistical analysis. Typical numbers cannot be guaranteed, but it does represent most possible standards.

(3) CIN, COUT, C1, and C2: Low ESR surface paste for setting electrical characteristics (MLCC).

Electrical characteristics (1) (2) (continued)

The limit of the standard font is suitable for TJ u003d 25OC. The limit of black body characters is suitable for the entire work knot temperatureFees (-30 ° C ≤TJ≤+105 ° C). Unless otherwise explained, specifications are suitable for LM2770 typical application circuits (page 1), where: vin u003d 3.6V; v (en) u003d vSEL u003d 1.8V, v (dormant) u003d 0V, CIN u003d COUT u003d 10 μF, C1 u003d C2 u003d 1.0 μF. (3)

(4) The efficiency is measured by the vehicle identification number (VIN). Between 4.2V scanning with small increment. The average value is calculated based on these values. The calculation is average.

(5) There is a 300K drop -down resistor between EN pin and GND

Typical performance features

Unless there are other regulations: CIN u003d 10 μF, C1 u003d 1.0μF, C2 u003d 1.0 μF, COUT u003d 10 μF, TA u003d 25OC. The capacitor is a low ESR multi -layer ceramic capacitor (MLCC).

Overview

LM2770 is a switch capacitor converter, generating a adjustable low -voltage output. The core of the part is a high -efficiency charge pump that uses multiple score gain and pulse frequency modulation (PFM) in a wider input voltage and output current range to minimize power loss. The main operating characteristics of LM2770 are divided into the following parts: PFM regulations, multiple -gain charge pumps, and multi -gain efficiency performance. Each chapter refers to a square diagram.

PFM regulations

LM2770 through pulse frequency modulation (PFM) adjustment to achieve strict adjustment output voltage. PFM is simply speaking that components only need to pass the charge to the output end to keep the output voltage adjustment. When the output voltage is higher than the target adjustment voltage, the component is vacated and consumed the minimum power current. In this state, the load current is only stored in the output capacitor. When the capacitor discharges and the output voltage is lower than the target adjustment voltage, the charging pump is started, and the charge is transported to the output end. The charge provides a load current and increases the voltage on the output capacitor. The main advantage of PFM adjustment is that when the output current is small, and the components are mainly in a low -power supply current. The net power supply is the smallest, because the parts only need to recharge the capacitor by starting the charge pump. With the adjustment of PFM, the frequency changes in the input and output ripples are obvious, and it depends on the output current, input voltage, and to a small degree of other factors, such as temperature and internal switching characteristics.

The core of the score multi -gain charge pump

The core of the lm2770 is a non -overlapping control generated insideTwo -phase charge pump clock. The charge pump transmits from the input to the output by using external flight capacitors C1 and C2. The two stages of the switch cycle are called ""charging phase"" and ""maintained/static phase"". During the charging phase, the flight capacitor was charged by the input power. After charging the flight capacitor, the switching cycle [t u003d 1/(2 × FSW)], LM2770 is switched to the maintenance/static stage. In this configuration, the charge stored on the flight capacitor during the charging phase is transferred to the output end. If the voltage is turned on when the switching cycle is over, the output voltage is lower than the target adjustment voltage, and the charge pump will be switched back to the charging phase. However, if the output voltage is higher than the target adjustment voltage switching cycle, the charge pump will be kept/static. It will be idle in this mode until the output voltage is lower than the target adjustment voltage. When this happens, the LM2770 will switch back to the charging state stage. The input, output and intermediate connections of flight capacitors are achieved with internal MOS switches. This LM2770 uses two flying capacitors and a multi -function switch network to achieve three different score voltage returns: #8531;, #189; and #8532;. With this gain switching ability, it seems that the LM2770 is one of the three charge pumps. The current ""active"" charge pump is currently the current situation of the charged pump that generates the highest efficiency of the charged pump based on the input and output.

Multi -gain efficiency performance

The ability to switch gain based on input and output conditions can be operated throughout LM2770. The efficiency of the charge pump is exported by the following two ideal equations (the power supply is simply, and the current and other losses are ignored): IIN u003d g x iOUT E u003d (VOUT x IOUT) ÷ (vin x IIN) u003d VOUT ÷ (g x vin) (1) In the formula, G represents the charge pump gain. When G × Vin is close to VOUT, the efficiency is the highest. For detailed efficiency data, see the efficiency chart in the typical performance characteristics part. This gain area is clearly distinguished through the sharp discontinuous discomfort in the efficiency curve, and at the bottom of each graph (g u003d #8532;, g u003d #189; g u003d #8531;).

Dynamic output voltage selection

The output voltage of LM2770 can be dynamically adjusted to improve system efficiency. Each LM2770 version contains two built -in output voltage options: high levels and low levels (1.5V and 1.2V, for example). Using simple VSEL logic input pins, the output voltage can be switched between these two voltages. Dynamic voltage selection can be used to improve the efficiency of the entire system. When comparing the system efficiency, between the two different output voltages, assessment power consumption is usually more insightful than the actual situation. Applications with lithium ion batteries are a good example to illustrate this. Reference LM2770 efficiency curve (see typical performance characteristics), all LM2770 output voltage options work in the case of the voltage range of the core lithium battery (3.5V-3.9V) g u003d #189;. Therefore, the LM2770 circuit will be within half of the output current within the core lithium ion voltage range without considering the output voltage (IIN u003d G × IOUT). Although the output voltage of LM2770 does not directly improve the system efficiency, it can have a secondary effect. Different output voltages usually cause different LM2770 load currents. This is where the system efficiency can benefit from the dynamic output voltage selection: LM2770 load can run at a lower current. This reduces the LM2770 input current and improves the overall efficiency of the system.

The dormant mode bypass LDO

LM2770 provides a low noise performance of the low -voltage differential stabilizer (LDO) under the negative load. It can provide output currents up to 20 mAh. This LDO has a low ground pins current, which is an ideal spare operation. LDO activates through dormant logic input pins. When sleep activation, the charge pump is banned, and the LDO provides all load current.

Close

When the voltage on the enable pin (EN) is low logic, the LM2770 is in the shutdown mode. When shutting down, LM2770 has almost no power current. During the shutdown, the output of the LM2770 was completely disconnected from the input. The internal feedback resistance will lower the output voltage to 0V (unless the output is driven by the external source). In some applications, the LM2770 may be disabled and the source of the pins of the pins is used with another voltage. This can be done, but the voltage on the LM2770 output pin cannot be higher than the input voltage. Due to internal feedback, when the external drive, the output pin will consume a small amount of current resistance between the Vout and GND.

Soft activation

LM2770 uses a soft startup circuit to prevent excessive pouring current during the startup process. When starting, the output voltage gradually rises from 0V to the rated output voltage. This situation occurs within 200 μs (typical). Soft startup is the joint of the component, including the voltage of the vehicle identification number (VIN) at the same time EN and pins.

Hot shutdown

The protection of overheating related damage is achieved through the heat clearance function. When the temperature of the intersection rises to 150OC (typical values), the part is switched to the stop mode. The lm2770 disconnects the knot temperature of the thermal part to be closed when the knot temperature of the heat is 140OC (typical value). Due to the LM2770, when the parts of the parts in the specified input voltage, output current, and ambient temperature work rated value. If the heat cycle is seen in these cases, the most likely reason is that the PCB layout is insufficient, and the heat is not allowed to completely dissipate from the WSON package.

Short -circuit current protection

The circuit contained in the LM2770 charge pump can be brokenThe protection equipment output is short -circuited to the ground when the bad fault. The short -circuit protection circuit limits the output current at 400 mAh (typical value) when the output voltage is lower than 165mV (typical values). The dormant mode LDO contains a 60MA (typical) current restriction circuit.

Recommended capacitor type

LM2770 requires 4 external capacitors to work normally. Multi -layer ceramic capacitors are recommended on the surface. These capacitors are small in size, cheap, and the equivalent series resistance is very low (ESR, ≤15m typical value). -Capacitors, OS-CON capacitors, and aluminum electrolytic capacitors are not recommended to be used with LM2770, because ESR is higher than ceramic capacitors. For most applications, LM2770, which is preferred to have a ceramic capacitor with X7R or X5R temperature characteristics. These capacitors have strict capacitors (up to ± 10%) and maintain their value exceeding the temperature (X7R: ± 15%higher than -55OC to 125OC; X5R: ± 15%higher than -55OC to 85OC). Capacitors of Y5V or Z5U temperature characteristics are usually not recommended to LM2770. These types of capacitors usually have a wide capacitor tolerance (+80%, -20%), and the change is significantly super temperature (Y5V: +22%, -82%, -30 ° C ~+85 ° C; Z5U: +22 %, -56%,+10 ° C to+85OC range). Under certain conditions, the capacitor value of Y5V or Z5U capacitors with a rated value of 1 μF can be as low as 0.1 μF. This harmful deviation may cause Y5V and Z5U capacitors to not meet the capacitor requirements of the minimum value LM2770.

The net capacitance of ceramic capacitors decreased with the increase of DC bias. This degeneration will cause the input and/or output capacitors to exceed expectations, resulting in higher ripple voltage and current. The use of DC bias is significantly lower than the capacitor rated voltage capacitor, which usually minimizes DC bias. For information about the DC bias characteristics of the electric container, please consult a capacitor manufacturer. Capacitor characteristics with different application conditions, capacitor types and capacitors manufacturers. It is strongly recommended to choose from the mass -produced container. This will help ensure that any such variable IN capacitance will not have a negative impact on the performance of the circuit.

The following table lists some leading ceramic capacitors

output capacitance and output voltage ripples

in the circuit in the LM2770 circuit The output capacitor directly affects the size of the output voltage ripple. The main factors that affect the output voltage ripple also include input voltage, output current and flight capacitors. Due to the complexity of multiple gains and PFM switches, the size of the equation or model wave pattern similar to the multi -gain and PFM switch is not easy to achieve. However, an important conclusion can be obtained: increasing (reduced) output capacitors will cause the output voltage to decrease (increase) ripples proportionally. This can beObserved typical performance features in the output voltage lines.

In a typical large current application, it is recommended to use 10 μF low ESR ceramic output capacitors. Different output capacitors can be used to reduce ripples, reduce the size of solutions and/or reduce the cost of solutions. However, replacing the output capacitor may also need to replace the wire capacitor and/or input capacitors to maintain good overall circuit performance. The performance of the LM2770 set up by different capacitors was discussed. The high ESR in the output capacitor increases the output voltage ripple. If you use ceramic capacitors on the output side, you do not need to worry, because the ESR of ceramic capacitors is usually very low, and only the minimum ESR has the impact of ripple size. If the type of different capacitors (such as 钽) with high ESR is used, ESR may cause high ripples. In order to eliminate this effect, the net output ESR can significantly reduce the low ESR ceramic capacitors in parallel with the main transition capacitance in the following way. The low ESR capacitor of ceramics will be parallel to the higher ESR, so as to generate low -net ESR reduction resistance according to the principle of parallel.

Due to the PFM characteristics of LM2770, the voltage ripples are the highest in light load. To eliminate this fluctuation, when the load current is less than equal to 20mA, consider running LM2770 in the dormant mode. Sleep mode disables the charge pump and the internal low -noise side linear regulator (LDO).

Entering capacitors and input voltage ripples

Input capacitors (CIN) are a charge storage, helping fast transfer electric containers from power to flight from power supply to flying in the charging phase. When the input capacitor helps keep the input voltage as the flight capacitor connects to the input terminal, the charging phase begins to sag. It can also filter noise on the input pin, keeping this noise away from the sensitive internal analog circuit, which is deviated from the input cable. Just like the relationship between the output capacitor and the output voltage ripple, the input capacitor has a explicit and first -order effect of the input ripple value. Increased (reduced) input capacitors will cause a decrease (increase) input voltage ripple. This can observe the waveform of the typical performance characteristics in the input voltage ripple. The input voltage, output current and flight capacitors will also affect the input ripple level to a certain extent. In a typical large current application, it is recommended to use 10 μF low ESR ceramic capacitors at the input end. Different input capacitors can be used to reduce ripples, reduce solution size and/or reduce solutions. However, changing the input capacitor may also need to change the overall circuit performance of the flying capacitor and/or output capacitors. The performance of LM2770 under different capacitors is discussed in the recommended capacitor configuration below.

Flight capacitor

Flight capacitor (C1 and C2) transmits the charge from the input terminal to the output end. Flight capacitors will affect the output current capacity and ripple size of the two. If the flight capacitor is too small, LM2770 may not be availableWhen the load current is high, the output voltage is adjusted. On the other hand, if the flight capacitor is too large, the flight capacitor may overwhelm input and output capacitors, resulting in increased input and output. Flight capacitors should be the same. As a general criterion, the capacitor value of each flight capacitor should be 1/10 of the output capacitor, and the maximum does not exceed 1 μF. This is suggestions, not requests. Polarized capacitors (钽, aluminum electrolytic, etc.) may not be used during flight. However, the capacitor may occur in reverse bias during the LM2770 operation.

Recommended capacitor configuration

The data in Table 1 can be used to help select the electrical requirements of the capacitor configuration size and cost and application of the best balanced solution (ripple voltage, output current capacity, etc.) Essence As mentioned earlier, the input and output ripple voltage and frequency will change a large current and input voltage with the output. The provided numbers show the expected ripple voltage current between VIN u003d 3.6V and loading between 100mA and 250mA. The table provides a preliminary ripple approximate value and provides a relatively different capacitor configuration, but it is not to ensure performance. The list of minimum input voltage recommendations shows that the capacitance of smaller flights has the ability to charge pump output current. Use smaller flight capacitors to increase the resistance of the output charging pump. Therefore, the minimum input voltage capacitor using a small flight application may need to be set slightly higher to prevent the output exceed the adjustment range during load.

(1) For more information on the data in this table, see the text in the ""Recommended Capacitor Configuration"" part

Layout Guide [

[ 123] The correct circuit board layout will help ensure the best performance of the LM2770 circuit. The following criteria are recommended:

Place the capacitor at the position near LM2770 as much as possible, preferably the same side as the IC on the circuit board.

Use a short and wide trace wire to connect the external capacitor to LM2770 to minimize the wire resistance and inductance as much as possible.

Low -resistance connection is used between grounding and GND pins of LM2770. It is the most favorable to connect GND to the ground layer on the circuit board with broad traces and/or pores.