Features

Maintain a constant frequency under low output

dual N -channel MOSFET synchronous driver

A programmable fixed frequency (PLL can be locked) [ 123]

Wide Vin range: 3.5V to 36V operations

Super efficiency

Extremely low pressure drop operation: 99%duty cycle

low pressure difference, 0.5A 0.5A, 0.5A Linear regulator, used for VPP generation or low noise sound audio supply

Built -in -power power resolution timer

Able to soft start

Low -power detector

] Remote output voltage detection

Foldable flow limit (optional)

Pinocar output voltage

Logical control micro -power shutdown: IQ LT; 30 μA

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[ 123] Output voltage from 1.19V to 9V

provides 28 and 36 lead SSOP packaging

Application

notebook and palm computer, PDA

Portable Instrument

Battery power supply device

DC power distribution system

LTC #174; 1438/LTC1439 is a dual synchronous antihypertensive switch regulator controller control The device is used to drive the external lock phase N -channel power MOSFET frequency architecture. The adaptive PowerTM output stage selectively drives the two N -channel MOSFETs up to 400kHz in the frequency, while reducing the high efficiency of switching loss and low output current. Use an external PNP 0.5A auxiliary linear regulator PASS device to provide a source of low noise and low voltage difference. Second winding feedback control pins (SFB1) ensure that the adjustment is not affected by the main load through forced continuous operation output. An additional comparator can be used as a low -value battery detector. Including a signal of a delay of 65536/FCLK (typical value of 300MS) output within 5%of the specified value generated by the power -on retirement timer (POR). The internal resistor division provides one of the two outputs of the optional output voltage when the remote sensing function is turned on. The operating current can detect the resistor through the user programming external current. The wide input power range allows working within the range of 3.5V to 30V (maximum 36V).

Typical application

Absolute maximum rated value

Input power supply voltage (VIN) 36V to -0.3V

The upper drive voltage (voltage 1,2) 42V to -0.3V

The switch voltage (SW1, 2) VIN+5V to -5V

EXTVCC voltage10V至–0.3V

POR2，LBO电压12V至-0.3V

AUXFB电压20V至-0.3V

AUXDR电压28V至-0.3V

[ 123] Sensory +1, sensory +2, sensory -1, sensory -2,

Vosense2 voltage INTVCC+0.3V to -0.3V

vprog1, vprog2 voltage INTVCC to –0.3V [ 123]

PLL LPF, ITH1, ITH2 voltage 2.7V to –0.3V

Oakson, Oakson B1,

Run/ss1, run/ss2, LBI voltage 10V 10V To — 0.3V

Peak output current lt; 10μs (TGL1, 2, BG1, 2) 2A

Peak output current lt; 10μs (TGS1, 2) 250 mia

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123] INTVCC output current 50 mAh

The working environment temperature range

Commercial 0 ° C to 70 ° C

Industry ─ 40 ° C to 85 ° C

Jacking temperature (Note 1) 125 degrees Celsius

Storage temperature range –65 ° C to 150 ° C

Lead temperature (welding, 10 seconds) 300 degrees Celsius

Electrical characteristics TA 25 ° C, VIN 15V, VRUN/SS1,2 5V, unless there are other instructions.

Electric characteristics TA 25 ° C, vin 15V, vRUN/SS1,2 5V, unless there is another instructions.

indicates the standard temperature range suitable for the entire operation.

Note 1: TJ calculates according to the environmental temperature TA and power

The PD is dissipated in accordance with the following formulas:

LTC1438CG, LTC1439CG: TJ TA+(PD) (95 ° C) (95 ° C) (95 ° C) (95 ° C) (95 ° C) (95 ° C) (95 ° C) (95 ° C) /W)

LTC1439CGW: TJ TA+(PD) (85 ° C/W)

Note 2: LTC1438 and LTC1439 test in the feedback loop to bring Vosense1, 2 servo to error amplifier Balance point (vitamin 1,2 1.19V).

Note 3: Since the grid charge is transmitted at the switch frequency. See application information.

Note 4: By measuring COSC charge and discharge current (iOSC) and application formula: FOSC (kHz) 8.4 (108) [COSC (PF)+11] –1 (1/ICHG+1/IDISC) - 1

Note 5: The auxiliary regulator is tested to the balance point of the error amplifier in the servo circuit. For Vauxdr GT; 9.5V, VauxFB uses internal resistor division. Check the application information department.

Typical performance features

pin function

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VIN: The main power is attracted. The signal of the IC must be grounded.

INTVCC: Internal 5V regulator and ExtVCC switch. Drive and control circuit are powered by the voltage. It must be at least 2.2 μF or electrolytic capacitors. In the following cases, the INTVCC regulator is very low. Reference LTC1538/LTC1539 is suitable for 5V without charging applications. Enter the external power supply to the internal switch. This opening is turned off into INTVCC power supply, bypassing the interior when EXTVCC is higher than 4.7V. Connecting this pin to the VOUT output voltage of the controller is higher. The voltage on this pin should not exceed 10 volts. Do you see the ExtVCC connection of the application information part.

Promotioner 1, Pusher 2: Supply to the upper part. Guide capacitors return to these other stitches. The voltage swing on these pins from INTVCC to VIN+INTVCC.

SW1, SW2: The connection between the opening node to the inductor. The voltage fluctuations of these pins came from the groundwalk (external) grounding voltage of the Schottki diodes to VIN. Small signal ground. The two controllers are shared by the ( -) terminals that are separated from a large current to the COUT capacitor.

PGND: Drive power ground. Connected to the ( -) terminals connected to the bottom of the source of the source. Sense – 1, Sense – 2: The ( -) input current comparator connected to. Except for the LTC1438-Adj, the VOUT sensing point connected to the first controller in the Sense-1. The first controller can only be used as a 3.3V or 5.0V regulator, and the VPROG1 pin controls LTC1438, LTC1438X and LTC1439. LTC1438-ADJ controller 1 implements a adjustable remote sensor. The second controller can be set to 3.3V, 5.0V, or a adjustable regulator controlled by VPROG2 pin (see Table 1).

pin function

Sense+1, sense+2: (+) input comparator of each current. Sense – 1 and Sense+1 pin set the current check threshold (andThe second controller is the same). Receive the feedback output terminal from the external sensor from VO2. VPROG2 pin determines which point Vosense2 must be connected. This Vosense1 pin can only be available on the LTC1438-ADJ, and a external resistor division is required to set the output voltage.

VPROG1, VPROG2: Programming internal voltage atxiser for output voltage induction. The first is the internal connection of the voltage sensor to the Sense -1, and the Vosense2 pin allows the second remote sensing controller. For VPROG1, VPROG2 LT; Vintvcc/3, except an output voltage set to 3.3V. For VPROG1, VPROG2 GT; Vintvcc/1.5, the frequency division is set to 5V for the output voltage. Keep VPROG2 open (DC) to allow the output to be connected to Vosense2 with the voltage resistor division of the second controller set by the external device. COSC: The frequency of external capacitors from this pin to grounding device works.

ITH1, ITH2: error putting the compensation point. Each related current comparator threshold will increase the control voltage.

RUN/SS1, RUN/SS2: Soft start control and RUN combination control input. The capacitors that are grounded in each pin set the slope time to the full current output. It's time for about 0.5S/μF. Press these needle foots below 1.3V to turn the special controller of the circuit required for IC. Press these two stitches at 1.3V below to completely close the device. For 5V applications, please refer to the LTC1538-AUX/LTC1539.

TGL1, TGL2: MOSFET MOSFET. These are floating output voltage switching amplitude equal to the INTVCC driver on SW1 and SW2.

TGS1, TGS2: MOSFET MOSFET with a small top N channel. These are the output voltage of the floating drive. Open TGS1 or TGS2 to call the controller for the controller.

BG1, BG2: The bottom large current door drive output N -channel MOSFET. The voltage swing on these pins comes from ground to InTVCC.

SFB1: Second winding feedback input. This input function is only on the first controller, and is usually connected to the secondary winding feedback resistor division. Pulling this pin to below 1.19V will be forced to continue to run synchronously. This other needle should be

tied to: continuous combat of ground forces; INTVCC in applications that do not use a second winding; and the resistance division can use a second winding in the application.

POR2: This lossIt is the consumption of the N -channel drop -down. When the output voltage of the output voltage controller of the second pin drops 7.5%, and the second controller of the 65536 oscillator cycle is re-released after the output voltage, the values u200bu200bof the second controller rose to the -5%of its adjustment value. When RUN/SS1 and RUN, POR2 output/SS2 is very low, which has nothing to do with VOUT2. This pinch is not running on the LTC1438X.

LBO: This output is a consumption of the N -channel drop -down. When the LBI pin is lower than 1.19V, the pin will absorb current.

LBI: The (+) input of the comparator can be used as a low -battery voltage detector. ( -) The input has been connected to the internal benchmark of 1.19V.

PLLIN: The external input of the phase detector. The pin is connected to SGND at the internal end with 50K #8486; The tie is not using the lock ring.

Locking loop LPF: The output of the phase of the phase is output and control the input oscillator. Usually the series of RC low -pass filter network is from this pin. Tie this needle on SGND without using a loop. You can choose from 0V to 2.4V logic signal.

Auxfb: Auxiliary regulator/COM Auxiliary Form feedback input. When used as a linear regulator, the input can be connected to an external resistor division or directly connected to the collector 12V operation of the external PNP transmission device. When it is used as a comparator, it is the non -reversible input of the reverse input comparator to connect to the internal 1.19V reference voltage. See the application part of the auxiliary regulator.

Oakson: Pull this pin height to open the auxiliary regulator/comparator. The threshold is 1.19V. This is an open/off input of streamlined power logic control.

AUXDR: The opening output/comparator of the auxiliary regulator. When used as a linear regulator, the base of the external PNP device is connected to the pin. Ann needs to use the external pull -up resistor as a comparative device. The voltage larger than 9.5V on the AUXDR causes the internal 12V resistor division to connect to the AUXFB pin.

Operation (reference function map)

Main control circuit

LTC1438/LTC1439 uses constant frequency and current mode reduction architecture. During the normal operation, when the oscillator works, the MOSFET at the top is opened at each cycle to set the RS 闩 lock, when the main current comparator I1 reset the RS lock. The current of the peak inductor I1 reset the RS 闩 lock is controlled by the control of the ITH1 (ITH2) pin, which is the output error amplifier (EA) of each pin. VPROG1 pin, such as the function in the pin, allow EA to receive the output feedback voltage of the selective attenuation sensor VFB 1 – 1 needle. At the same time, VPROG2 and Vosense2 allow EAOr an external resistance receiving output feedback voltage on the second controller on the VFB2. When the load current increases, ventricular fibrillation will cause ventricular fibrillation relative to the 1.19V reference voltage, which will cause the ITH1 (ITH2) voltage to increase until the average electrical sensor current matches the new load current. After the large top MOSFET has been closed, the MOSFET at the bottom is turned on until the inductor current starts to reverse, such as the current of the current comparator i2, or the start of the next cycle. The top MOSFET driver is from the floating start band capacitor CB, usually in each turnover cycle. When the VIN is approached, the cycle may enter the Dropout and try to continue opening the top MOSFET. Attenuation detector calculates the oscillating cycle MOSFET keeps opening, and periodic forced to close the time to allow CB to charge.

The main control circuit is low through the slice closing/SS1 (run/ss2) pins. Released/SS1 (Run/SS2) allows the internal 3 μA current source to be a soft -start charging capacitor CSS. When the CSS reaches 1.3V, the main control part is ITH1 (ITH2) voltage at about 30%of the maximum value. As CSS continues to charge, iTH1 (ITH2) is gradually released, allowing normal operations. When the/SS1 and RUN/SS2 are low at the same time, all LTC1438/LTC1439 functions are closed. Reference LTC1538-AUX/LTC1539 Data 5V keeps thin plates with electricity applications. The comparator OV prevents the transient super adjustment gt; 7.5%off the top MOSFET and keeps off until the fault has been excluded.

Low -current operation

The adaptive power supply mode allows LTC1439 to automatically switch between two output levels to adapt to different output stage load currents. TGL1 (TGL2) and BG1 (BG2) pins drive large -scale synchronous N -channel MOSFET high current, while TGS1 (TGS2) pins drive small N -channel MOSFET and Schottky diode at low current. This allows the load current to decrease without causing large MOSFET grid charge loss. If the TGS1 (TGS2) pin is kept open, the cycle defaults to the basis of the large MOSFET intermittent work of the emergencies. The adaptive power mode provides a constant frequency operation, which is reduced to about 1%of the rated load current. This causes a load current to reduce a order of magnitude before the emergency mode operation begins. There is no small MOSFET (that is, no adaptive power mode) to transition to an emergency mode operation is about the rated load current.

When the COM PARTOR I2 detects the current reversal and close the bottom MOSFET. If the voltage on RSENSE exceeds the lagging full cycle of I2 (about 20mV), and then in the next cycle, the top drive is connected to the TGS1 (TGS2) pin and BG1 small MOSFET (BG2) PIN has been disabled. Until the peak value of the inductors exceeds 20mV/RSENSE or ITH1 (ITH2) voltage exceeding 0.6V, both cases will cause the driver to return to the TGL1 (TGL2) pin in the next cycle. Even if the load current has other regulations, the two situations will be mandatory and continuously operate in the same operation. First, when the co-mode sensing +1 (sensing +2) and the sensing-1 voltage (sensing-2) pins are less than 1.4V, the other is when the SFB1 pin is lower than 1.19V. The latter case is used to assist the second winding adjustment, as described in the application information part.

Frequency synchronization

There is a lock ring (PLL) on the LTC1439 to connect the oscillator with the external synchronization power supply to the PLLIN pin. The phase detector on the PLL LPF pin is also controlled by controlling inputs in the range of 0 to 2.4 volts. After locking, the locking loop will rising the penetration signal of the top MOSFET on the top of the top MOSFET. When PLLIN keeps opening, the PLL LPF becomes lower, forcing the oscillator to minimize the frequency.

Powering and reset

POR2 pins are a second controller that drives output, lowered the second controller of the main point output voltage. When the output voltage rises to 7.5%of the regulation range, the timer starts Por2 after the oscillator cycle of 216 (65536). This feature is not available on the LTC1438X.

Auxiliary linear regulator

Auxiliary linear regulator in LTC1439 controls the external PNP transistor, and the working current is as high as 500 mAh. A When the AUXDR pin is higher than 9.5V, it is easy to implement the 12VVPP supply. When AUXDR is lower than 8.5V, an external feedback distribution can be used to set other output voltage. Oakson's low customs control regulator provides convenient logic control power supply.

AUX block can be used as a comparator

Reverse input is connected to the internal 1.19V reference. This AUXDR pins are used as output, which requires the external pull to the power supply below 8.5V to suppress the calling internal resistor division.

INTVCC/EXTVCC power supply

At the top and bottom MOSFET driver and MOST power supply of other LTC1438/LTC1439 circuit intVCC pins. The bottom MOSFET drive power supply is also connected to INTVCC. When the ExtVCC pin is kept open, an internal 5V low -voltage differentializer is powered by INTVCC. If EXTVCC voltage is higher than 4.8V, the 5V regulator is turned off and turned on to connect EXTVCC to INTVCC. This allows the export of INTVCC power from an high -efficiency external source, such as the output regulator itself orThe second winding, as described in the application information part.

Application information

Basic LTC1439 application circuit is shown in Figure 1. The selection of external components starts with the choice of RSENSE. RSENSE is known once, COSC and L can choose. Next is to choose power MOSFET and D1. Finally, CIN and COUT were selected. The circuit shown in FIG. 1 can be configured to run at up to 28V input voltage (due to external MOSFET).

The RSENSE select

Select RSENSE according to the required output current. The maximum threshold of the LTC1438/LTC1439 current comparator is 150MV/RSense, and the mode range from the public line SGND to INTVCC. The current comparator threshold sets the peak of the electrical sensor current, which generates the maximum average output current IMAX equal to half of the peak value minus the peak ripple current, #8710; IL. Leave some room for the changes of LTC1438/LTC1439 and external component values:

LTC1438/LTC1439 and RSENSE value from 0.005 #8486; to 0.2 #8486 ;.

COSC selection of working frequency

LTC1438/LTC1439 adopts a constant frequency structure, and the frequency determines the oscillator capacitor on the COSC by the external device. Each MOSFET on the upper part is opened, and the voltage on the COSC is reset to ground. On time, COSC is voltage (only LTC1439) from a fixed current plus an additional current phase detector (VPLLLLPF) that is proportional to the output. When the voltage on the capacitor reaches 1.19V, COSC is reset to the ground. Then repeat this process. The value of COSC is the frequency calculated based on the expected operation. Assuming that there is no external oscillator input (vplllpf 0V):

The relationship between choosing cosc u200bu200band frequency is given More, reduce efficiency (see efficiency precautions). The recommended maximum switching frequency is 400kHz. When using Figure 2 to synchronize, select the COSC corresponding frequency of about 30%of the center. (See the synchronization of the loop and the frequency).

Calculation of the inductor value

The working frequency of the working frequency is related to the choice of the sensor, because the higher operating frequency allows the use of inductance and capacitance value to be compared Small. So why is anyone choosing a larger part of working at a lower frequency? The answer is efficiency. Higher frequency usually causes reduced efficiency because MOSFET grid charge loss. Except when this basic trade is cut off,The influence of inductance value on the ripple current must also consider the current operation. The inductance value has a direct impact on the ripple current. This inductor ripple current #8710; IL decreases with the increase of inductance or frequency, and increases with the increase of VIN or VOUT:

Application information

Accept large #8710; IL value allows low inductance, but it will cause higher output voltage ripples and larger core losses. A reasonable starting point tidal wave current is #8710; IL 0.4 (IMAX). Remember, the maximum #8710; IL appears under the maximum input voltage. The inductance value also affects low -current. Began to turn to low -current running as an inductor current to zero and the bottom MOSFET. The lower inductor value (higher #8710; IL) will occur under high load current to cause efficiency decreased operation within the upper limit range of low current. In the emergencies operation (TGS1, 2 pins are broken), the lower inductance value will lead to a reduction frequency. Figure 3 gives the recommended inductive value and operating frequency and voltage range

The value of the inductor iron core

Once the value of L is known, the type of induction must be selected. High -efficiency converters generally cannot withstand the iron heart loss of low -cost powder iron heart, forcing the use of more expensive ferrite, molybdenum alloy or Kool Mμ #174; core. The actual iron heart loss is not related to the iron heart. The size is a fixed inductor value, but it is a very dependent choice inductor. As the inductance increases, the iron heart losses. Unfortunately, increasing inductances requires more wire turns and copper loss. The iron oxygen design has a very low iron heart loss, which is the first choice at high switching frequency. Therefore, the design target can be concentrated in copper loss and prevent saturation. The saturated ""hard"" of ferrite core material means that the peak design current exceeds. This caused the inductors to suddenly increase the ripple current and the output voltage ripples that came. Do not let the core saturate! Molypermalloy (from Magnetics, INC.) Is a very good core material loss of low ring, but it is better than iron oxygen. The reasonable compromise solution of the same manufacturer is KOOL MM. The ring is very space -saving, especially when you can use several layers of wires. Because they generally do not have a line axis, it is difficult to install. However, the design of the surface paste is not significantly increased.

Power MOSFET and D1 select

must choose three external power MOSFETLTC1439 controller for each choice: a pair of N -channel MOSFET for the top (main) switch and the bottom (synchronization) at the bottom (synchronization) switch. Only one top MOSFET is needed for each LTC1438 controller. In order to use the adaptive power output level, the two must choose the upper module MOSFET. A large [low RSD (on)] requires MOSFET andA small [higher RDS (on)] MOSFET.Large MOSFET is used as a main switch and combined with synchronous switches.This smaller MOSFET can only enable conditions at low load current.The advantage of this is that the low to the mid -to -mid -current improves efficiency while continuing to run at a constant frequency.In addition, by using small MOSFETs, the circuit will maintain a constant frequency switch to a lower frequency current and a delayed jump cycle.

The RDS (ON) recommended by the small MOSFET is about 0.5 #8486;Be careful not to use RDS (on) too low; remember, we must save the door charge.(Higher RDS (ON) MOSFET has a smaller grid capacitor, so less current is required to charge the charging door).For all LTC1438 and cost -sensitive LTC1439 applications, no small MOSFET is required.Then when the load current decreases, it begins to operate the emergency mode.