View IRU3146_189208.PDF datasheet online --- IC-ON-LINE

Datasheet File OCR Text:

Data Sheet No.PD 94702
IRU3146
DUAL SYNCHRONOUS PWM CONTROLLER WITH CURRENT SHARING CIRCUITRY AND AUTO-RESTART FEATURES
Dual Synchronous Controller with 180 out-of-phase Configurable to 2-Independent Outputs or 2-Phase Single Output Current Sharing Using Inductor's DCR Current Limit using MOSFET's RDS(ON) Hiccup/Latched Current Limit Latched Over-Voltage Protection Vcc from 4.5V to 16V Input Programmable Switching Frequency up to 500KHz Two Independent Soft-Starts/ Shutdowns 0.8V Precision Reference Voltage Available Power Good Output External Frequency Synchronization
DESCRIPTION
The IRU3146 IC combines a Dual synchronous Buck controller, providing a cost-effective, high performance and flexible solution. The IRU3146 can configured as 2independent or as 2-phase controller. The 2-phase configuration is ideal for high current applications. The IRU3146 features 180 out of phase operation which reduces the required input/output capacitance and results to few number of capacitor quantity. Other key features offered by this device include two independent programmable soft starts, programmable switching frequency up to 500KHz per phase, under voltage lockout function. The current limit is provided by sensing the lower MOSFET's on-resistance for optimum cost and performance.
2-Phase Power Supply Graphic Card DDR Memory Applications
D1 C12
APPLICATIONS
Embedded Computer Systems Telecom Systems Point of Load Power Architectures
12V
C11 C3 C4 C13 Q2 C14 L3
VCL VcH1 VOUT3 VcH2 Vcc HDrv1 OCSet1 Hiccup Sync VREF LDrv1 PGnd1 VP2
C5
R1
Q3
R5 C15 R10
1.8V @ 30A C16
R2 C8 R3
Rt
U1 IRU3146
D2 BAT54A
VSEN1 VSEN2 Fb1 Fb2 C17
R11
R7
Comp1
R9 C18 L4
R8
C9
R4
Comp2
HDrv2 OCSet2
R6
Q4 Q5
PGood C10
PGood SS1 / SD SS2 / SD
LDrv2 PGnd2 Gnd
Figure 1 - Typical application of IRU3146 in 2-phase configuration with inductor current sensing
PACKAGE ORDER INFORMATION
DEVICE IRU3146CF
Rev. 1.1 6/25/04
PACKAGE 28-Pin TSSOP (F) www.irf.com
1
IRU3146
ABSOLUTE MAXIMUM RATINGS
Vcc, VCL Supply Voltage .............................................. -0.5V To 16V VcH1 and VcH2 Supply Voltage ................................ -0.5V To 25V PGOOD................. ................................................... -0.5V To 16V Storage Temperature Range ...................................... -40C To 125C Operating Junction Temperature Range ..................... -40C To 125C
Caution: Stresses above those listed in Absolute Maximum Ratings" may cause permanent damage to the device.
PACKAGE INFORMATION
28-PIN TSSOP (F)
PGood 1 VCC 2 VOUT3 3 Rt 4 VSEN2 5 Fb2 6 Comp2 7 SS2 / SD 8 OCSet2 9 VcH2 10 HDrv2 11 PGnd2 12 LDrv2 13 VCL 14
28 Gnd 27 VREF 26 VP2 25 Hiccup 24 Sync 23 VSEN1 22 Fb1 21 Comp1 20 SS1 / SD 19 OCSet1 18 VcH1 17 HDrv1 16 PGnd1 15 LDrv1
JA = 84C/W
ELECTRICAL SPECIFICATIONS
Unless otherwise specified, these specifications apply over Vcc=12V, VcH1=VcH2=VCL=12V and TA=0 to 70C. Typical values refer to TA=25C. Low duty cycle pulse testing is used which keeps junction and case temperatures equal to the ambient temperature. PARAMETER Reference Voltage Section Reference Voltage Voltage Line Regulation UVLO Section UVLO Threshold - Vcc UVLO Hysteresis - Vcc UVLO Threshold - VcH1 UVLO Hysteresis - VcH1 UVLO Threshold - VcH2 UVLO Hysteresis - VcH2 Supply Current Section Vcc Dynamic Supply Current VcH1 & VcH2 Dynamic Current VCL Dynamic Supply Current Vcc Static Supply Current VcH1/VcH2 Static Current VCL Static Supply Current SYM VREF LREG TEST CONDITION MIN 0.789 5Rev. 1.1 6/25/04
UVLOVCC Supply Ramping Up Ramp Up and Ramp Down UVLOVCH1 Supply Ramping Up Ramp Up and Ramp Down UVLOVCH2 Supply Ramping Up Ramp Up and Ramp Down Dyn ICC Dyn ICH Dyn ICL ICCQ ICHQ ICLQ Freq=300KHz, CL=1500pF Freq=300KHz, CL=1500pF Freq=300KHz, CL=1500pF SS=0V SS=0V SS=0V www.irf.com
15 25 25 15 10 10
2
IRU3146
PARAMETER Soft-Start Section Charge Current Power Good Section VSENS1 Lower Trip Point VSENS2 Lower Trip Point PGood Output Low Voltage Error Amp Section Fb Voltage Input Bias Current Transconductance 1 Transconductance 2 Error Amp Source/Sink Current Input Offset Voltage for PWM1/2 VP2 Voltage Range Oscillator Section Frequency Ramp Amplitude Synch Frequency Range Synch Pulse Duration Synch High Level Threshold Synch Low Level Threshold VOUT3 Internal Regulator Output Voltage Output Current Protection Section OVP Trip Threshold OVP Fault Prop Delay Current Limit Threshold Current Source Hiccup Duty Cycle Hiccup High Level Threshold Hiccup Low Level Threshold Output Drivers Section Rise Time Fall Time Dead Band Time Max Duty Cycle Min Duty Cycle Min Pulse Width Thermal Shutdown Trip Point Thermal Shutdown Hysteresis SYM SSIB PGFB1L PGFB2H TEST CONDITION SS=0V VSENS1 Ramping Down VSENS2 Ramping Down ISINK=2mA SS=3V 1400 1400 60 -5 0.8 MIN 20 TYP 25 MAX 32 UNITS A V V V A mho mho A mV V KHz Freq VRAMP Rt(SET) to 30K Note1 20% above free running freq Note1 Note1 255 1.25 800 200 2 300 0.8 5.9 50 OVP
Output forced to 1.125VREF,Note1
0.8VREF 0.9VREF 0.95VREF 0.8VREF 0.9VREF 0.95VREF 0.1 0.5 -0.1 -0.5 2300 2300 140 +5 1.5
IFB1 gm1 gm2 VOS(ERR)2 VP2
Fb to VREF Note1
100 0
345 V KHz ns V V V mA V s A % V V ns ns ns % % ns C C
6.2
6.7
OCSet Hiccup pin pulled high, Note1
1.1VREF 1.15VREF 1.2VREF 5 16 20 24 5
Note1
2 0.8
Tr Tf TDB DMAX DMIN Puls(min)
CL=1500pF, Figure 2 CL=1500pF, Figure 2 Figure 2 Fb=0.6V, FSW=300KHz Fb=1V FSW=300KHz, Note1 Note 1
18 25 50 85 0
150
50 50 100
140 20
Note 1: Guaranteed by design but not tested for production.
Rev. 1.1 6/25/04
www.irf.com
3
IRU3146
DEADBAND TIME
Tr 90% High Side Driver HD 2V 10% Tr 90% Low Side Driver LD 2V 10% Deadband H_to_L Deadband L_to_H Tf Tf
Figure 2 - Deadband time definition. TDB(TYP)=(Deadband H_toL+Deadband L_to -H)/2
PIN DESCRIPTIONS
PIN# 1 2 3 4 5,23 6,22 PIN DESCRIPTION Power Good pin. Low when any of the outputs fall 10% below the set voltages. Supply voltage for the internal blocks of the IC. Output of the internal LDO. Switching frequency setting resistor. (see Figure 10 for selecting resistor values). Sense pins for OVP and PGood. For 2-Phase operation tie these pins together. Inverting inputs to the error amplifiers. In current sharing mode, Fb1 is connected to a resistor divider to set the output voltage and Fb2 is connected to programming resistor to achieve current sharing. In independent 2-channel mode, these pins work as feedback inputs for each channel. Comp2, Comp1 Compensation pins for the error amplifiers. These pins provide soft-start for the switching regulator. An internal current source charges external capacitors that are connected from these pins to ground which ramp up the SS2 / SD output of the switching regulators, preventing them from overshooting as well as limiting SS1 / SD the input current. The converter can be shutdown by pulling these pins below 0.3V. OCSet2,OCSet1 Current limit resistor (RLIM) connection pins for output 1 and 2. The other ends of RLIMs are connected to the corresponding switching nodes. VcH2, VcH1 Supply voltage for the high side output drivers. These are connected to voltages that must be typically 6V higher than their bus voltages. A 1F high frequency capacitor must be connected from these pins to GND to provide peak drive current capability. HDrv2, HDrv1 Output drivers for the high side power MOSFETs. 1) PGnd2, PGnd1 These pins serve as the separate grounds for MOSFET drivers and should be connected to the system's ground plane. LDrv2, LDrv1 Output drivers for the synchronous power MOSFETs. VCL Supply voltage for the low side output drivers. This pin should be high for normal operation The internal oscillator may be synchronized to an external clock via this pin. Sync When pulled High, it puts the device current limit into a hiccup mode. When pulled Low, Hiccup the output latches off, after an overcurrent event. www.irf.com
Rev. 1.1 6/25/04
PIN SYMBOL PGood Vcc VOUT3 Rt VSEN2, VSEN1 Fb2,Fb1
7,21 8 20 9,19 10,18 11,17 12,16 13,15 14 24 25
4
IRU3146
PIN DESCRIPTIONS
PIN# 26 27 28 PIN SYMBOL VP2 VREF Gnd PIN DESCRIPTION Non-inverting input to the second error amplifier. In the current sharing mode, it is connected to the programming resistor. In independent 2-channel mode it is connected to VREF pin when Fb2 is connected to the resistor divider to set the output voltage. Reference Voltage. The drive capability of this pin is about 2uA. Analog ground for internal reference and control circuitry. Connect to PGnd plane with a short trace.
1) These pins should not go negative (-0.5V), this may cause instability for the gate drive circuits. To prevent this, a low forward voltage drop diode is required between these pins and ground as shown in Figure 1.
BLOCK DIAGRAM
Vcc
2
25uA 25uA
SS2 / SD SS1 / SD
POR
8 20
64uA Max 64uA
Mode
Bias Generator
4.2V / 4.0V
3V 0.8V POR
VP2 0.8V
Mode Control
POR Mode
18
VcH1 HDrv1
VcH1 VcH2
3.5V / 3.3V 3.5V / 3.3V
UVLO
17
0.3V PWM Comp1 Error Amp1 0.8V Thermal Shutdown SS1
14 15
VCL LDrv1 PGnd1 OCSet1
R Q
Ramp1 Set1 Two Phase Oscillator Ramp2 3uA
SS1
16
Fb1 Comp1 Rt Sync VREF
22
S
19
21
Reset Dom Set2 Reset Dom
20uA
4
10 11
VcH2 HDrv2 Hiccup
24
S
0.8V Error Amp2 PWM Comp2
27
Q R
SS1 SS2 Mode 0.3V
Hiccup Control
25
VP2 Fb2 Comp2 VSEN1 VSEN2 Gnd
26 13 12
LDrv2 PGnd2 OCSet2
6
SS2
7 23 5 28
SS2
PGood / OVP
OVP HDrv OFF / LDrv ON
9
3uA
20uA
1
PGood VOUT3
Regulator
3
Figure 3 - Block diagram of IRU3146.
Rev. 1.1 6/25/04
www.irf.com
5
IRU3146
FUNCTIONAL DESCRIPTION
Introduction The IRU3146 is versatile device for high performance Buck converters. It is included of two synchronous Buck controllers which can be operated both in two independent mode or in 2-phase mode. The timing of the IC is provided through an internal oscillator circuit. These are two out-of-phase oscillators that can be programmed up to 400KHz per phase. Supply Voltage Vcc is the supply voltage for internal controller. The operating range is from 4.5V to 16V. It also is fed to the internal LDO. When Vcc is below under-voltage threshold, all MOSFET drivers will be turned off. Internal Regulator The regulator powers directly from VCC and generates a regulated voltage (Typ. 6.2V@50mA). The output is protected for short circuit. This voltage can be used for charge pump circuitry as describe in Figure12. Input Supplies UnderVoltage LockOut The IRU3146 UVLO block monitors three input voltages (VCC, VCH1 and VCH2) to ensure reliable start up. The MOSFET driver output turn off when any of the supply voltages drops below set thresholds. Normal operation resumes once the supply voltages rise above the set values. Independent Mode In this mode the IRU3146 provides control to two independent output power supplies with either common or different input voltages. The output voltage of each individual channel is set and controlled by the output of the error amplifier, which is the amplified error signal from the sensed output voltage and the reference voltage. The error amplifier output voltage is compared to the ramp signal thus generating fixed frequency pulses of variable duty-cycle, which are applied to the FET drivers, Figure18 shows a typical schematic for such application. 2-Phase Mode This feature allows to connect both outputs together to increase current handling capability of the converter to support a common load. The current sharing can be done either using external resistors or sensing the DCR of inductors (see Figure 4). In this mode, one control loop acts as a master and sets the output voltage as a regular Voltage Mode Buck controller and the other control loop acts as a slave and monitors the current Figure 5 - 30A Current Sharing using Inductor sensing
(5A/Div)
information for current sharing. The voltage drops across the current sense resistors (or DCR of inductors) are measured and their difference is amplified by the slave error amplifier and compared with the ramp signal to generate the PWM pulses to match the output current. In this mode the SS2 pin should be floating.
IRU3146 PWM Comp1 Master E/A 0.8V Fb1 VP2 FB2 L2 Slave E/A R2 C2 RL2 L1 R1 RL1 VOUT Comp
PWM Comp2
C1
Figure 4 - Loss-less inductive current sensing and current sharing. In the diagram, L1 and L2 are the output inductors. RL1 and RL2 are inherent inductor resistances. The resistor R1 and capacitor C1 are used to sense the average inductor current. The voltage across the capacitors C1 and C2 represent the average current flowing into resistance RL1 and RL2. The time constant of the RC network should be equal or at most three times larger than the time constant L1/R . L1 R1xC1=(1~3)x ---(1) RL1
L1
6
www.irf.com
Rev. 1.1 6/25/04
IRU3146
Dual Soft-Start The IRU3146 has programmable soft-start to control the output voltage rise and limit the inrush current during start-up. It provides a separate Soft-Start function for each outputs. This will enable to sequence the outputs by controlling the rise time of each output through selection of different value soft-start capacitors. The soft-start pins will be connected together for applications where, both outputs are required to ramp-up at the same time. To ensure correct start-up, the soft-start sequence initiates when the VCC, VCH1 and VCH2 rise above their threshold (4.2V and 3.5V respectively) and generate the Power On Reset (POR) signal. Soft-start function operates by sourcing an internal current to charge an external capacitor to about 3V. Initially, the soft-start function clamps the E/A's output of the PWM converter. During power up, the converter output starts at zero and thus the voltage at Fb is about 0V. A current (64A) injects into the Fb pin and generates a voltage about 1.6V (64Ax25K) across the negative input of E/A and (see Figure6). The magnitude of this current is inversely proportional to the voltage at soft-start pin. The 25A current source starts to charge up the external capacitor. In the mean time, the soft-start voltage ramps up, the current flowing into Fb pin starts to decrease linearly and so does the voltage at negative input of E/A. When the soft-start capacitor is around 1V, the current flowing into the Fb pin is approximately 32A. The voltage at the positive input of the E/A is approximately: 32Ax25K = 0.8V The E/A will start to operate and the output voltage starts to increase. As the soft-start capacitor voltage continues to go up, the current flowing into the Fb pin will keep decreasing. Because the voltage at pin of E/A is regulated to reference voltage 0.8V, the voltage at the Fb is: VFB = 0.8-(25KxInjected Current) The feedback voltage increases linearly as the injecting current goes down. The injecting current drops to zero when soft-start voltage is around 2V and the output voltage goes into steady state. Figure 7 shows the theoretical operational waveforms during soft-start.
25uA 25uA
SS2 / SD SS1 / SD
POR
8 20
64uA Max 64uA
Error Amp1 0.8V
Fb1 Comp1 VP2 Fb2 Comp2
22 21
Error Amp2
26
6 7
Figure 6 -Soft-start circuit for IRU3146
Output of POR 3V
2V
Soft-Start Voltage Current flowing into Fb pin 0V 64uA 0uA
1V
Voltage at negative input 1.6V of Error Amp
0.8V 0.8V
Voltage at Fb pin
0V
Figure 7 - Theoretical operational waveforms during soft-start. The output start-up time is the time period when softstart capacitor voltage increases from 1V to 2V. The start-up time will be dependent on the size of the external soft-start capacitor. The start-up time can be estimated by: 25AxTSTART/CSS = 2V-1V
Rev. 1.1 6/25/04
www.irf.com
7
IRU3146
For a given start up time, the soft-start capacitor can be calculated by: CSS 25AxTSTART/1V The soft-start is part of Over Current Protection scheme, during the overload or short circuit condition the external soft start capacitors will be charged and discharged in certain slope rate to achieve the hiccup mode function.
25uA Hiccup
The internal current source develops a voltage across RSET. When the low side switch is turned on, the inductor current flows through the Q2 and results a voltage which is given by: VOCSET = IOCSETxRSET-RDS(ON)xiL
IOCSET
---(2)
IRU3146
OCSet RSET Hiccup Control
Q1 L1 Q2 VOUT
SS1 / SD
20
3uA
Figure 8 - 3uA current source for discharging soft start-capacitor during Hiccup mode Out-of-Phase Operation The IRU3146 drives its two output stages 180 out-ofphase. In 2-phase configuration, the two inductor ripple currents cancel each other and result in a reduction of the output current ripple and yield a smaller output capacitor for the same ripple voltage requirement. In single input voltage applications, the input ripple current reduces. This result in much smaller input capacitor's RMS current and reduces the input capacitor quantity. Over-Current Protection The IRU3146 can provide two different schemes for OverCurrent Protection (OCP). When the pin Hiccup is pulled high, the OCP will operate in hiccup mode. In this mode, during overload or short circuit, the outputs enter hiccup mode and stay in that mode until the overload or short circuit is removed. The converter will automatically recover. When the Hiccup pin is pulled low, the OCP scheme will be changed to the latch up type, in this mode the converter will be turned off during Overcurrent or short circuit. The power needs to be recycled for normal operation. Each phase has its own independent OCP circuitry. The OCP is performed by sensing current through the RDS(ON) of low side MOSFET. As shown in Figure 9, an external resistor (RSET) is connected between OCSet pin and the drain of low side MOSFET (Q2) which sets the current limit set point. If using one soft start capacitor in dual configuration for a precise power up the OCP needs to be set to latch mode.
Figure 9 - Diagram of the over current sensing. The critical inductor current can be calculated by setting: VOCSET = IOCSETxRSET - RDS(ON)xIL = 0 RSETxIOCSET ISET = IL(CRITICAL)= RDS(ON) ---(3)
The value of RSET should be checked in an actual circuit to ensure that the Over Current Protection circuit activates as expected. The IRU3146 current limit is designed primarily as disaster preventing, "no blow up" circuit, and is not useful as a precision current regulator. In two independent mode, the output of each channel is protected independently which means if one output is under overload or short circuit condition, the other output will remain functional. The OCP set limit can be programmed to different levels by using the external resistors. This is valid for both hiccup mode and latch up mode. In 2-phase configuration, the OCP's output depends on any one channel, which means as soon as one channel goes to overload or short circuit condition the output will enter either hiccup or latch-up, dependes on status of Hiccup pin.
8
www.irf.com
Rev. 1.1 6/25/04
IRU3146
Frequency Synchronization The IRU3146 is capable of accepting an external digital synchronization signal. Synchronization will be enabled by the rising edge at an external clock. Per-channel switching frequency is set by external resistor (Rt). The free running oscillator frequency is twice the per-channel frequency. During synchronization, Rt is selected such that the free running frequency is 20% below the sync frequency. Synchronization capability is provided for both 2output and 2-phase configurations. When unused, the Sync pin will remain floating and is noise immune. Thermal Shutdown Temperature sensing is provided inside IRU3146. The trip threshold is typically set to 140 C. When trip threshold is exceeded, thermal shutdown turns off both FETs. Thermal shutdown is not latched and automatic restart is initiated when the sensed temperature drops to normal range. There is a 20 C hysteresis in the shutdown threshold. Power Good The IRU3146 provides a power good signal. The power good signal should be available after both outputs have reached regulation. This pin needs to be externally pulled high. High state indicates that outputs are in regulation. Power good will be low if either one of the output voltages is 10% below the set value. There is only one power good for both outputs. Over-Voltage Protection OVP Over-voltage is sensed through separate VOUT sense pins Vsen1 and Vsen2. A separate OVP circuit is provided for each output. Upon over-voltage condition of either one of the outputs, the OVP forces a latched shutdown on both outputs. In this mode, the upper FET drivers turn-off and the lower FET drivers turn-on, thus crowbaring the outputs. Reset is performed by recycling either Vcc. Error Amplifier The IRU3146 is a voltage mode controller. The error amplifiers are of transconductance type. In independent mode, each amplifier closes the loop around its own output voltage. In current sharing mode, amplifier 1 becomes the master which regulates the common output voltage. Amplifier 2 performs the current sharing function. Both amplifiers are capable of operating with Type III compensation control scheme. Low Temperature Start-Up The controller is capable of starting at -40 C ambient temperature. Operation Frequency Selection The optimum operating frequency range for IRU3146 is 300KHz per phase, theoretically the IRU3146 can be operated at higher switching frequency (e.g. 500KHz). However the power dissipation for IC, which is function of applied voltage, gate drivers load and switching frequency, will result in higher junction temperature of device. It may exceed absolute maximum rating of junction temperature, figure 18 (page 16) shows case temperature versus switching frequency with different capacitive loads. This should be considered when using IRU3146 for such application. The below equation shows the relationship between IC's maximum power dissipation and Junction temperature: J-A Pd = JA Where: Tj: Maximum Operating Junction Temperature (125C) TA: Ambient Temperature (70C) JA = Thermal Impedance of package (84C/W) For Tj=125C TA=70C and JA=84C/W This will result to power dissipation of 650mW, this includes biasing current for all four external MOSFETs and IC's biasing current. The switching frequency is determined by an external resistor (Rt). The switching frequency is approximately inversely proportioned to resistance (see Fig 10).
Per channel Switching Frequency vs. RT
700 650 Switching Frequency in KHz 600 550 500 450 400 350 300 250 200 10 20 30 RT(Kohm) 40 50
Figure 10- Switching Frequency versus External Resistor.
Shutdown The outputs can be shutdown independently by pulling the respective soft-start pins below 0.3V. This can be easily done by using an external small signal transistor. During shutdown both MOSFETs will be turned off. During this mode the LDO will stay on. Cycling softstart pins will clear all fault latches and normal operation will resume.
Rev. 1.1 6/25/04
www.irf.com
9
IRU3146
APPLICATION INFORMATION
Design Example: The following example is a typical application for IRU3146, the schematic is Figure18 on page17. VIN = 12V VOUT(2.5V) = 2.5V @ 10A VOUT(1.8V) = 1.8V @ 10A VOUT = Output voltage ripple 3% of VOUT FS = 300KHz Output Voltage Programming Output voltage is programmed by reference voltage and external voltage divider. The Fb1 pin is the inverting input of the error amplifier, which is referenced to the voltage on non-inverting pin of error amplifier. For this application, this pin (VP) is connected to reference voltage (VREF). The output voltage is defined by using the following equation: R6 VOUT = VP x 1 + ---(4) R5 Soft-Start Programming The soft-start timing can be programmed by selecting the soft-start capacitance value. The start-up time of the converter can be calculated by using: Css 25xtSTART (F) ---(5)
Where tSTART is the desired start-up time (ms) For a start-up time of 4ms for both output, the soft-start capacitor will be 0.1F. Connect ceramic capacitors at 0.1F from SS1 pin and SS2 pin to GND. Supply VCH1 and VCH2 To drive the high side switch, it is necessary to supply a gate voltage at least 4V grater than the bus voltage. This is achieved by using a charge pump configuration as shown in Figure 12. This method is simple and inexpensive. The operation of the circuit is as follows: when the lower MOSFET is turned on, the capacitor (C1) charges up to VOUT3, through the diode (D1). The bus voltage will be added to this voltage when upper MOSFET turns on in next cycle, and providing supply voltage (VCH1) through diode (D2). Vc is approximately: VCH1 VOUT3 + VBUS - (VD1 + VD2) Capacitors in the range of 0.1F and 1F are generally adequate for most applications. The diode must be a fast recovery device to minimize the amount of charge fed back from the charge pump capacitor into VOUT3. The diodes need to be able to block the full power rail voltage, which is seen when the high side MOSFET is switched on. For low voltage application, schottky diodes can be used to minimize forward drop across the diodes at start up.
D1 VOUT3 VCH1 C3 D2 VBUS C2 C1 Q1 L2
(
)
VP2 = VREF = 0.8V When an external resistor divider is connected to the output as shown in Figure 11.
VOUT
IRU3146
VREF VP Fb
R6 R5
Figure 11 - Typical application of the IRU3146 for programming the output voltage. Equation (4) can be rewritten as: VOUT R6 = R5 x -1 VP
(
)
Will result to: VOUT(2.5V) = 2.5V VREF = 0.8V R9= 2.14K, R5= 1K
VOUT(1.8V) = 1.8V VREF = 0.8 R7= 1.24K, R8 = 1K
Regulator
If the high value feedback resistors are used, the input bias current of the Fb pin could cause a slight increase in output voltage. The output voltage can be set more accurately by using low value, precision resistors.
IRU3146
HDrv
Q2
Figure 12 - Charge pump circuit.
10
www.irf.com
Rev. 1.1 6/25/04
IRU3146
Input Capacitor Selection The 1800 out of phase will reduce the RMS value of the ripple current seen by input capacitors. This reduces numbers of input capacitors. The input capacitors must be selected that can handle both the maximum ripple RMS at highest ambient temperature as well as the maximum input voltage. The RMS value of current ripple for duty cycles under 50% is expressed by: IRMS= (I D1(1-D1)+I D2(1-D2)-2I1I2D1D2) --- (6)
2 1 2 2
For i(1.8V) = 30%(IO(1.8V) ), then the output inductor will be: L3 = 1.7H Panasonic provides a range of inductors in different values and low profile for large currents. Choose ETQP6F1R8BFA (1.71H, 14A, 3.3m) both for L3 and L4. For 2-phase application, equation (7) can be used for calculating the inductors value. In such case the inductor ripple current is usually chosen to be between 1040% of maximum phase current. Output Capacitor Selection The criteria to select the output capacitor is normally based on the value of the Effective Series Resistance (ESR). In general, the output capacitor must have low enough ESR to meet output ripple and load transient requirements, yet have high enough ESR to satisfy stability requirements. The ESR of the output capacitor is calculated by the following relationship: (ESL, Equivalent Series Inductance is neglected) VO ESR ---(8) IO Where: VO = Output Voltage Ripple i = Inductor Ripple Current VO = 3% of VO will result to ESR(2.5V) =19.7m and ESR(1.8V) =16m The Sanyo TPC series, Poscap capacitor is a good choice. The 6TPC330M, 330F, 6.3V has an ESR 40m. Selecting two of these capacitors in parallel for 2.5V output, results to an ESR of 20m which achieves our low ESR goal. And selecting four of these capacitors in parallel for 1.8V output, results to an ESR of 10m which achieves our low ESR goal. The capacitors value must be high enough to absorb the inductor's ripple current. Power MOSFET Selection The IRU3146 uses four N-Channel MOSFETs. The selections criteria to meet power transfer requirements is based on maximum drain-source voltage (VDSS), gatesource drive voltage (VGS), maximum output current, Onresistance RDS(ON) and thermal management. The both control and synchronous MOSFETs must have a maximum operating voltage (VDSS) that exceeds the maximum input voltage (VIN).
Where: IRMS is the RMS value of the input capacitor current D1 and D2 are the duty cycle for each output I1 and I2 are the current for each output For this application the IRMS =4.8A For higher efficiency, low ESR capacitors is recommended. Choose two Poscap from Sanyo 16TPB47M (16V, 47F, 70m ) with a maximum allowable ripple current of 1.4A for inputs of each channel. Inductor Selection The inductor is selected based on operating frequency, transient performance and allowable output voltage ripple. Low inductor value results to faster response to step load (high i/t) and smaller size but will cause larger output ripple due to increase of inductor ripple current. As a rule of thumb, select an inductor that produces a ripple current of 10-40% of full load DC. For the buck converter, the inductor value for desired operating ripple current can be determined using the following relation: VIN - VOUT = Lx i VOUT 1 ; t = Dx ;D= t VIN fS VOUT L = (VIN - VOUT)x ---(7) VINxixfS Where: VIN = Maximum Input Voltage VOUT = Output Voltage i = Inductor Ripple Current fS = Switching Frequency t = Turn On Time D = Duty Cycle
For i(2.5V) = 38%(IO(2.5V) ), then the output inductor will be: L4 = 1.71H
Rev. 1.1 6/25/04
www.irf.com
11
IRU3146
The gate drive requirement is almost the same for both MOSFETs. Logic-level transistor can be used and caution should be taken with devices at very low VGS to prevent undesired turn-on of the complementary MOSFET, which results a in shoot-through. The total power dissipation for MOSFETs includes conduction and switching losses. For the Buck converter, the average inductor current is equal to the DC load current. The conduction loss is defined as: PCOND(Upper Switch) = ILOADxRDS(ON)xDx PCOND(Lower Switch) = ILOADxRDS(ON)x(1 - D)x = RDS(ON) Temperature Dependency The RDS(ON) temperature dependency should be considered for the worst case operation. This is typically given in the MOSFET data sheet. Ensure that the conduction losses and switching losses do not exceed the package ratings or violate the overall thermal budget. Choose IRF7457 both for control and synchronous MOSFET. This device provide low on-resistance in a compact SOIC 8-Pin package. The MOSFET have the following data: IRF7457 VDSS = 20V ID = 15A RDS(ON) = 7m The total conduction losses for each output will be: PCON(TOTAL, 2.5V) = PCON(UPPER) + PCON(LOWER) PCON(TOTAL, 2.5V) = 1.0W PCON(TOTAL, 1.8V) = PCON(UPPER) + PCON(LOWER) PCON(TOTAL, 1.8V) = 1.0W The switching loss is more difficult to calculate, even though the switching transition is well understood. The reason is the effect of the parasitic components and switching times during the switching procedures such as turn-on / turnoff delays and rise and fall times. The control MOSFET contributes to the majority of the switching losses in a synchronous Buck converter. The synchronous MOSFET turns on under zero voltage conditions, therefore, the switching losses for synchronous MOSFET can be neglected. With a linear approximation, the total switching loss can be expressed as:
10% VGS td(ON) tr td(OFF) tf
2 2
PSW =
VDS(OFF) tr + tf ---(9) x x ILOAD T 2 Where: VDS(OFF) = Drain to Source Voltage at off time tr = Rise Time tf = Fall Time T = Switching Period ILOAD = Load Current
VDS 90%
Figure 13 - Switching time waveforms. From IRF7457 data sheet we obtain: IRF7457 tr = 16ns tf = 7ns These values are taken under a certain condition test. For more details please refer to the IRF7457 data sheet. By using equation (9), we can calculate the total switching losses. PSW(TOTAL,2.5V) = 0.414W PSW(TOTAL,1.8V) = 0.414W Programming the Over-Current Limit The over-current threshold can be set by connecting a resistor (RSET) from drain of low side MOSFET to the OCSet pin. The resistor can be calculated by using equation (3). The RDS(ON) has a positive temperature coefficient and it should be considered for the worse case operation. RDS(ON) = 7mx1.5 = 10.5m ISET IO(LIM) = 10Ax1.5 = 15A (50% over nominal output current) This results to: RSET = R1=R6=7.8K
12
www.irf.com
Rev. 1.1 6/25/04
IRU3146
Feedback Compensation The IRU3146 is a voltage mode controller; the control loop is a single voltage feedback path including error amplifier and error comparator. To achieve fast transient response and accurate output regulation, a compensation circuit is necessary. The goal of the compensation network is to provide a closed loop transfer function with the highest 0dB crossing frequency and adequate phase margin (greater than 45 ). The output LC filter introduces a double pole, -40dB/ decade gain slope above its corner resonant frequency, and a total phase lag of 180 (see Figure 14). The Resonant frequency of the LC filter is expressed as follows: 1 FLC = ---(10) 2x LOxCO Where: Lo is the output inductor For 2-phase application, the effective output inductance should be used Co is the total output capacitor Figure 14 shows gain and phase of the LC filter. Since we already have 180 phase shift just from the output
Gain 0dB -40dB/decade Phase 0
The ESR zero of the output capacitor is expressed as follows: FESR = 1 2xESRxCo ---(10A)
VOUT R6 Fb
R5 Vp=VREF
Gain(dB)
E/A
Comp C9 R4
Ve
H(s) dB
FZ
Frequency
Figure 15 - Compensation network without local feedback and its asymptotic gain plot. The transfer function (Ve / VOUT) is given by:
H(s) = gmx
(
R5 1 + sR4C9 x R6 + R5 sC9
)
---(11)
FLC Frequency
-180
FLC
Frequency
Figure14 - gain and phase of LC filter The IRU3146's error amplifier is a differential-input transconductance amplifier. The output is available for DC gain control or AC phase compensation. The E/A can be compensated with or without the use of local feedback. When operated without local feedback, the transconductance properties of the E/A become evident and can be used to cancel one of the output filter poles. This will be accomplished with a series RC circuit from Comp pin to ground as shown in Figure 15. Note that this method requires the output capacitor to have enough ESR to satisfy stability requirements. In general, the output capacitor's ESR generates a zero typically at 5KHz to 50KHz which is essential for an acceptable phase margin.
The (s) indicates that the transfer function varies as a function of frequency. This configuration introduces a gain and zero, expressed by: |H(s=jx2xFO)| = gmx FZ = 1 2xR4xC9 R5 xR4 R6+R5 ---(13) ---(12)
|H(s)| is the gain at zero cross frequency. First select the desired zero-crossover frequency (FO1): FO1 > FESR and FO1 (1/5 ~ 1/10)xfS
Rev. 1.1 6/25/04
www.irf.com
13
IRU3146
1 VOSC FO1xFESR R5 + R6 x x x gm VIN FLC2 R5 For a general solution for unconditional stability for ceramic output capacitor with very low ESR or any type of output capacitors, in a wide range of ESR values we should implement local feedback with a compensation network. The typically used compensation network for a voltage-mode controller is shown in Figure 16.
ZIN C10 R8 R6 Fb R5 Vp=VREF
Gain(dB)
R4 =
---(14)
Where: VIN = Maximum Input Voltage VOSC = Oscillator Ramp Voltage FO1 = Crossover Frequency FESR = Zero Frequency of the Output Capacitor FLC = Resonant Frequency of the Output Filter R5 and R6 = Resistor Dividers for Output Voltage Programming gm = Error Amplifier Transconductance For V2.5V: VIN = 12V VOSC = 1.25V FO1 = 30KHz FESR = 12KHz FLC = 4.75KHz R5 = 1K R6 = 2.14K gm = 2000mho
VOUT R7
C12 C11 Zf
E/A
Comp
Ve
This results to R4=2.61K Choose R4=2.61K To cancel one of the LC filter poles, place the zero before the LC filter resonant frequency pole: FZ 75%FLC 1 FZ 0.75x ---(15) 2 LO x CO For: Lo = 1.71H FZ = 3.56KHz Co = 660F R4 = 2.61K Using equations (13) and (15) to calculate C9, we get: C9 17.18nF; Choose C9 =18nF Same calcuation For V1.8V will result to: R3 = 2.8K and C8 = 22nF One more capacitor is sometimes added in parallel with C9 and R4. This introduces one more pole which is mainly used to suppress the switching noise. The additional pole is given by: 1 FP = C9xCPOLE 2xR4x C9 + CPOLE The pole sets to one half of switching frequency which results in the capacitor CPOLE: 1 1 CPOLE = xR4xfS 1 xR4xfS C9 fS for FP << 2
H(s) dB
FZ1
FZ2
FP2
FP3
Frequency
Figure 16- Compensation network with local feedback and its asymptotic gain plot. In such configuration, the transfer function is given by: Ve 1 - gmZf = VOUT 1 + gmZIN The error amplifier gain is independent of the transconductance under the following condition: gmZf >> 1 and gmZIN >>1 ---(16) By replacing ZIN and Zf according to Figure 16, the transformer function can be expressed as: H(s) = (1+sR7C11)x[1+sC10(R6+R8)] 1 x sR6(C12+C11) C12C11 1+sR7 C12+C11 x(1+sR8C10)
[
(
)]
As known, transconductance amplifier has high impedance (current source) output, therefore, consider should be taken when loading the E/A output. It may exceed its source/sink output current capability, so that the amplifier will not be able to swing its output voltage over the necessary range. The compensation network has three poles and two zeros and they are expressed as follows:
14
www.irf.com
Rev. 1.1 6/25/04
IRU3146
FP1 = 0 FP2 = FP3 = 1 2xR8xC10 1 C12xC11 2xR7x C12+C11 1 2xR7xC11 Compensation for Slave Error Amplfier for 2-Phase Configuration The slave error amplifier is a differential-input transconductance amplifier, in 2-phase configuration the main goal for the slave feed back loop is to control the inductor current to match the masters inductor current as well provides highest bandwidth and adequate phase margin for overall stability. The following analysis is valid for both using external current sense resistor and using DCR of inductors. The transfer function of power stage is expressed by: G(s) = IL2(s) VIN - VOUT = Ve(s) sL2 x VOSC Where: VIN = Input Voltage VOUT = Output Voltage L2 = Output Inductor VOSC = Oscillator Peak Voltage ---(18)
(
)
1 2xR7xC12
FZ1 =
1 1 FZ2 = 2xC10x(R6 + R8) 2xC10xR6 Cross Over Frequency: VIN 1 FO = R7xC10x x VOSC 2xLoxCo Where: VIN = Maximum Input Voltage VOSC = Oscillator Ramp Voltage Lo = Output Inductor Co = Total Output Capacitors
---(17)
The stability requirement will be satisfied by placing the poles and zeros of the compensation network according to following design rules. The consideration has been taken to satisfy condition (16) regarding transconductance error amplifier. These design rules will give a crossover frequency approximately one-tenth of the switching frequency. The higher the band width, the potentially faster the load transient response. The DC gain will be large enough to provide high DC-regulation accuracy (typically -5dB to -12dB). The phase margin should be greater than 45 for overall stability. Based on the frequency of the zero generated by ESR versus crossover frequency, the compensation type can be different. The table below shows the compensation type and location of crossover frequency. Compensator Location of Zero Typical Type Crossover Frequency Output (FO) Capacitor Type II (PI) FPO < FZO < FO < fS/2 Electrolytic, Tantalum Type III (PID) FPO < FO < FZO < fS/2 Tantalum, Method A Ceramic Type III (PID) FPO < FO < fS/2 < FZO Ceramic Method B Table - The compensation type and location of zero crossover frequency. Details are dicussed in application Note AN-1043 which can be downloaded from the IR Web-Site.
Rev. 1.1 6/25/04
As shown the transfer function is a function of inductor current. The transfer function for the compensation network is given by equation (19), when using a series RC circuit as shown in Figure 17: D(s) = Ve(s) = RS2 x IL2(s) sC2R2 (gmx RS1)x(1 +sC2 ) ---(19) RS2
IL2 L2 Fb2 RS2 RS1 L1 IL1 Vp2 E/A2 Comp2 R2 C2 Ve
Figure 17 - The PI compensation network for slave channel. The loop gain function is: H(s)=[G(s) x D(s) x RS2] H(s)=RS2x RS1 VIN-VOUT (gmx RS2)x(1+sR2C2) x(sL2xVOSC) sC2
www.irf.com
15
IRU3146
Select a zero crossover frequency for control loop (FO2) 1.25 times larger than zero crossover frequency for voltage loop (FO1): Fo2 1.25%xF01 H(Fo) = Layout Consideration The layout is very important when designing high frequency switching converters. Layout will affect noise pickup and can cause a good design to perform with less than expected results. Start by placing the power components. Make all the connections in the top layer with wide, copper filled areas. The inductor, output capacitor and the MOSFET should be as close to each other as possible. This helps to reduce the EMI radiated by the power traces due to the high switching. Place input capacitor near to the drain of the high-side MOSFET. The layout of driver section should be designed for a low resistance (a wide, short trace) and low inductance (a wide trace with ground return path directly beneath it), this directly affects the driver's performance. To reduce the ESR, replace the one input capacitor with two parallel ones. The feedback part of the system should be kept away from the inductor and other noise sources and must be placed close to the IC. In multilayer PCB's, use one layer as power ground plane and have a separate control circuit ground (analog ground), to which all signals are referenced. The goal is to localize the high current paths to a separate loops that does not interfere with the more sensitive analog control function. These two grounds must be connected together on the PC board layout at a single point.
gmxRS1xR2x
VIN - VOUT =1 2xFoxL2xVOSC
---(20)
From (20), R2 can be express as: R2 = 1
gm x RS1
x 2 x FO2 x L2 x VOSC VIN - VOUT
---(21)
Set the zero of compensator to be half of FLC(SLAVE), the compensator capacitor, C2, can be calculated as: FLC(SLAVE) = Fz = C2 = 2 1 L2xCOUT
FLC(SLAVE) 2 1 2 x R2 x Fz ---(22)
When using the DCR of inductors as current sense element, replace RS1 in equation (21) with DCR value of inductor.
Switching Frequency vs. Case Temp
90 Case temp (oC) 80 70 60 50 40 30 200 300 400 500 600 700 100pF 1000pF 1800pF 3300pF
Freq (KHz)
Figure18- Case Temperature versus Switching Frequency at Room Temperature Test Condition: Vin=Vcl=Vch1=Vch2=12V, Capacitors used as loads for output drivers.
16
www.irf.com
Rev. 1.1 6/25/04
IRU3146
L1
12V
C12 1uF
D1 BAT54S
C1 47uF
1uH C2 47uF
C3 1uF
C4 1uF C5 1uF
VCL Vcc
VcH1 VOUT3 VcH2 HDrv1 OCSet1
C13 1uF R1 7.8K
C14 2x 47uF 16TPB47M Q2 IRF7457 Q3 IRF7457 VSEN1 D2 BAT54A
C11 0.1uF
L3 1.7uH R20 1.24K R21 1K R7 1.24K R8 1.8V @ 10A C16 4x 330uF, 40m 6TPB330M
Hiccup VP2 VREF R2 33K R3 C8 20nF 2.8K R4 C9 18nF 2.61K PGood C10 0.1uF Rt
LDrv1 PGnd1 Sync
U1 IRU3146
Comp1
VSEN1 VSEN1 VSEN2 VSEN2 Fb1 Fb2
Comp2
HDrv2 OCSet2
R6 7.8K
C17 2x 47uF 16TPB47M Q4 L4 IRF7457 Q5 IRF7457 VSEN2 1.7uH R22 2.24K R23 1K
R5 1K
1K
R9 2.14K
2.5V @ 10A
PGood SS1 / SD C15 0.1uF SS2 / SD
LDrv2 PGnd2 Gnd
C18 2x 330uF, 40m 6TPB330M
Figure 19 - Typical application of IRU3146. 12V input and two independent outputs.
Rev. 1.1 6/25/04
www.irf.com
17
IRU3146
TYPICAL OPERATING CHARACTERISTICS
Test Conditions: VIN=12V, VOUT1=2.5V, IOUT1=0-10A, VOUT2=1.8V, IOUT2=0-10A, Fs=300KHz
Figure 20 - Input Supply Ramps up. Ch1: 1.8V, Ch2: 2.5V, Ch3: Input Supply
Figure 21 - Input Supply Ramps up/down. Ch1: 1.8V, Ch2: 2.5V, Ch3: Input Supply
Figure 22 - Normal condition at No Load. Ch1: HDrv2, Ch2: HDrv1, Ch3 and Ch4: Inductor Currents
Ch3:ch4: 5A/div
Figure 23 - Normal condition at 10A Load. Ch1: HDrv2, Ch2: HDrv1, Ch3 and Ch4: Inductor Currents
Ch3:ch4: 5A/div
18
www.irf.com
Rev. 1.1 6/25/04
IRU3146
TYPICAL OPERATING CHARACTERISTICS
Test Conditions: VIN=12V, VOUT1=2.5V, IOUT1=0-10A, VOUT2=1.8V, IOUT2=0-10A, Fs=300KHz
Figure 24 - Soft_Start. Ch1: SS2, Ch2: 1.8V, Ch3: SS1, Ch4: 2.5V
Figure 25 - Soft_Start. Ch1: Vin, Ch2: Vout3(LDO), Ch3: SS2, Ch4: SS2
Figure 26 - Deadband Time (1.8V Output). Ch1: LDrv2, Ch2: HDrv2, Ch3: Switching Node
Figure 27 - Deadband Time (2.5V Output). Ch1: LDrv1, Ch2: HDrv1, Ch3: Switching Node
Rev. 1.1 6/25/04
www.irf.com
19
IRU3146
TYPICAL OPERATING CHARACTERISTICS
Test Conditions: VIN=12V, VOUT1=2.5V, IOUT1=0-10A, VOUT2=1.8V, IOUT2=0-10A, Fs=300KHz
Figure 28 - Shut Down (Pulling down the SS1 pin). Ch1: HDrv1, Ch2: LDrv1, Ch3: SS1
Figure 29 - Shut Down (pulling down the SS2 pin). Ch1: HDrv2, Ch2: LDrv2, Ch3: SS2
Figure 30 - High side and Low side Drivers peak Current for 1.8V Output Ch1: HDrv2, Ch2: LDrv2, Ch3: High Side Peak Current, Ch4: Low Side Peak Current
Ch3:ch4: 1A/div
Figure 31 - High side and Low side Drivers peak Current for 2.5V Output Ch1: HDrv1, Ch2: LDrv1, Ch3: High Side Peak Current, Ch4: Low Side Peak Current
Ch3:ch4: 1A/div
20
www.irf.com
Rev. 1.1 6/25/04
IRU3146
TYPICAL OPERATING CHARACTERISTICS
Test Conditions: VIN=12V, VOUT1=2.5V, IOUT1=0-10A, VOUT2=1.8V, IOUT2=0-10A, Fs=300KHz
Figure 32 - Load Transient Response. Ch2: 2.5V, Ch4: Step Load (0-10A)
Ch3:ch4: 5A/div
Figure 33 - Load Transient Response. Ch1: 1.8V, Ch3: Step Load (0-10A)
Ch3:ch4: 5A/div
Figure 34 - Power Good Signal Ch1: Input Supply, Ch2: 2.5V Output, Ch3: 1.8V Output, Ch4 : Power Good Signal
Figure 35 - Short Circuit Condition (Hiccup Mode). Ch1: SS1 pin, Ch2: SS2 pin, Ch3 and Ch4 : Inductor Currents
Ch3:ch4: 10A/div
Rev. 1.1 6/25/04
www.irf.com
21
IRU3146
TYPICAL APPLICATION
L1 12V C1 47uF 1uH C2 47uF
C12 1uF
D1 BAT54S
C11 0.1uF C3 1uF C4 1uF C5 1uF VCL Vcc VcH1 VOUT3 VcH2 HDrv1 OCSet1 Hiccup Sync VREF R2 33K C8 22nF 2.2K C6 120pF R4 C9 12nF 8K C7 82pF R3 Rt LDrv1 PGnd1 VP2 C13 1uF R1 12K C14 3x 47uF Q2 IRFR3706 Q3 IRFR3711 D2 BAT54A VSEN L3 1uH, 2m DCR R5 1K VSEN R21 1K C15 1uF R20 1.24K 1.8V @ 30A C16 8x 330uF, 40m 6TPB330M R7 1.24K R8 1K C18 1uF
U1 IRU3146
VSEN1 VSEN2 Fb1 Fb2
Comp1
Comp2
C17 3x 47uF HDrv2 OCSet2 R6 12K Q4 IRFR3706 Q5 IRFR3711
R9 1K L4
PGood C10 0.1uF
PGood SS1 / SD SS2 / SD
LDrv2 PGnd2 Gnd
1uH, 2m DCR
Figure 36 - 2-phase operation with inductor current sensing. 12V to 1.8V @ 30A output
22
www.irf.com
Rev. 1.1 6/25/04
IRU3146
TYPICAL APPLICATION
C12 1uF D1 BAT54S
L1 12V C1 47uF 1uH C2 47uF
C11 0.1uF C3 1uF C4 1uF C5 1uF VCL Vcc VcH1 VOUT3 VcH2 HDrv1 OCSet1 Hiccup Sync VREF R2 33K R3 C8 22nF 2.2K C6 120pF R4 C9 12nF 8K C7 82pF Rt LDrv1 PGnd1 VP2 C13 1uF R1 12K C14 3x 47uF Q2 IRFR3706 Q3 IRFR3711 D2 BAT54A VSEN L3 1uH R5 2m R20 1.24K
1.8V @ 30A C16 8x 330uF, 40m 6TPB330M
VSEN R21 1K
U1 IRU3146
VSEN1 VSEN2 Fb1 Fb2
Comp1
R7 1.24K R8 1K
Comp2
C17 3x 47uF HDrv2 OCSet2 R6 12K Q4 IRFR3706 Q5 IRFR3711 L4 1uH R9 2m
PGood C10 0.1uF
PGood SS1 / SD SS2 / SD
LDrv2 PGnd2 Gnd
Figure 37 - 2-phase operation with resistor current sensing. 12V to 1.8V @ 30A output
Rev. 1.1 6/25/04
www.irf.com
23
IRU3146
TYPICAL APPLICATION
L2 5V 1uH C18 150uF D3 BAT54S C20 1uF 12V C1 47uF L1 1uH C2 47uF C17 3x 150uF C19 0.1uF C13 1uF C12 1uF D1 BAT54S
C3 1uF
C4 1uF C5 1uF
VCL VcH1 VOUT3 VcH2 Vcc HDrv1 OCSet1 Hiccup Sync VREF LDrv1 PGnd1 VP2 R1 12K
C14 3x 47uF Q2 IRFR3706 Q3 IRFR3711 R5 1K
C11 0.1uF
L3 1uH, 2m DCR C21 1uF R20 1.24K R21 1K C22 1uF R7 1.24K R8 1K 1.8V @ 30A C16 8x 330uF, 40m 6TPB330M
R2 33K C8 22nF 2.2K C6 120pF R4 C9 4.7nF 23K C7 27pF PGood C10 0.1uF R3
Rt
U1 IRU3146
D2 BAT54A
VSEN1 VSEN2 Fb1 Fb2 HDrv2 Q4 IRFR3706 R6 12K Q5 IRFR3711 R9 1K L4 1uH, 2m DCR
Comp1
Comp2
OCSet2 PGood SS1 / SD SS2 / SD LDrv2 PGnd2 Gnd
Figure 38 - Typical application of IRU3146 using 5V and 12V supplies to generate single output voltage. 1.8V @ 30A using inductor sensing.
24
www.irf.com
Rev. 1.1 6/25/04
IRU3146
TYPICAL APPLICATION
L2 5V C18 150uF D3 BAT54S C20 1uF 12V C1 47uF L1 1uH C2 47uF 1uH C17 3x 150uF
C19 0.1uF C13 1uF C12 1uF D1 BAT54S
C3 1uF
C4 1uF C5 1uF
VCL VcH1 VOUT3 VcH2 Vcc HDrv1 OCSet1 Hiccup Sync VREF LDrv1 PGnd1 VP2 R1 15K
C14 3x 47uF Q2 IRFR3706 Q3 IRFR3711 D2 BAT54A
C11 0.1uF
L3 1uH
R5 2m R20 1.24K R21 1K
1.8V @ 30A C16 8x 330uF, 40m 6TPB330M
R2 33K R3 C8 22nF 2.2K C6 120pF R4 C9 4.7nF 23K C7 27pF PGood C10 0.1uF
Rt
U1 IRU3146
VSEN1 VSEN2 Fb1 Fb2 Q4 IRFR3706 Q5 IRFR3711
Comp1
R7 1.24K R8 1K
Comp2
HDrv2 OCSet2 LDrv2 PGnd2 Gnd
R6 10K
L4 1uH
R9 3m
PGood SS1 / SD SS2 / SD
Figure 39 - Typical application of IRU3146. 1.8V @ 30A output with 5V and 12V input and different input current setting. (5V @ 5A and 12V @ 3A)
Rev. 1.1 6/25/04
www.irf.com
25
IRU3146
TYPICAL APPLICATION
C12 1uF D1 BAT54S
L1 5V C1 47uF 1uH C2 47uF
C3 1uF
C4 1uF C5 1uF
VCL Vcc
VcH1 VOUT3
VcH2 HDrv1
C13 1uF R1 10K
C14 3x 330uF 6TPB330M Q2 IRF7457 Q3 IRF7460 VSEN1 D2 BAT54A
C11 0.1uF
L3 1uH R20 1.24K R21 1K R7 1.24K R8 1.8V @ 10A C16 4x 330uF, 40m 6TPB330M
OCSet1 Hiccup VP2 VREF LDrv1 PGnd1 Sync
R2 33K R3 C8 8.2nF 6K C6 47pF R4
Rt
U1 IRU3146
VSEN1 VSEN2 Fb1 Fb2
Comp1
C9 4.7nF 15K C7 PGood C10 0.1uF 27pF
Comp2
HDrv2 OCSet2
R6 8.5K
C17 3x 330uF 6TPB330M Q4 1/2 IRF7910 L4 Q5 1/2 IRF7910 3.3uH
R5 1K
1K
R9 2.14K
2.5V @ 5A
PGood SS1 / SD C15 0.1uF SS2 / SD
LDrv2 PGnd2 Gnd
C18 2x 330uF, 40m 6TPB330M
R22 2.14K VSEN2 R23 1K
Figure 40 - Single 5V input and two independent outputs.
26
www.irf.com
Rev. 1.1 6/25/04
IRU3146
TYPICAL APPLICATION
12V 5V C1 47uF
L1 1uH C2 47uF C14 3x 330uF 6TPB330M Q2 IRF7457 Q3 IRF7460 D2 BAT54A L3 1uH R20 1.24K VSEN1 R21 1K R7 1.24K R8 C17 3x 330uF 6TPB330M L4 3.3uH R22 2.14K VSEN2 R23 1K R5 1K R9 2.14K 1K 1.8V @ 10A C16 4x 330uF, 40m 6TPB330M
C3 1uF
C4 1uF C5 1uF
VCL Vcc
VcH1 VOUT3
VcH2 HDrv1
C13 1uF R1 10K
OCSet1 Hiccup VP2 VREF LDrv1 PGnd1 Sync
R2 33K R3 C8 8.2nF 6K C6 47pF R4 C9 4.7nF 15K C7 27pF PGood C10 0.1uF
Rt
U1 IRU3146
VSEN1 VSEN2 Fb1 Fb2
Comp1
Comp2
HDrv2 OCSet2
R6 5.1K
Q4 IRF7457 Q5 IRF7460
2.5V @ 5A
PGood SS1 / SD C15 0.1uF SS2 / SD
LDrv2 PGnd2 Gnd
C18 2x 330uF, 40m 6TPB330M
Figure 41 - Typical application of IRU3146. 5V input, 12V drive and two independent outputs.
Rev. 1.1 6/25/04
www.irf.com
27
IRU3146
TYPICAL APPLICATION
3.3V L1 5V C1 47uF 1uH C2 47uF C12 1uF D1 BAT54S
C3 1uF
C4 1uF C5 1uF
VCL Vcc
VcH1 VOUT3
VcH2 HDrv1
C13 1uF R1 8.5K
C14 2x 330uF 6TPB330M Q2 1/2 IRF7910 Q3 1/2 IRF7910 D2 BAT54A VSEN1
C11 0.1uF
L3 3.3uH R20 2.14K R21 1K 2.5V @ 5A C16 2x 330uF, 40m 6TPB330M
OCSet1 Hiccup VP2 VREF LDrv1 PGnd1 Sync
R2 33K R3 C8 4.7nF 15K C6 27pF R4 C9 5.6nF 8.2K C7 PGood C10 0.1uF 27pF
Rt
U1 IRU3146
VSEN1 VSEN2 Fb1 Fb2
Comp1
R7 2.14K R8 1K
Comp2
HDrv2 OCSet2
R6 8.5K
PGood SS1 / SD C15 0.1uF SS2 / SD
LDrv2 PGnd2 Gnd
C17 R5 2x 330uF 1K R9 Q4 6TPB330M L4 1.24K 1/2 IRF7910 1.8V @ 5A 2.2uH Q5 C18 1/2 IRF7910 2x 330uF, 40m 6TPB330M R22 1.24K VSEN2 R23 1K
Figure 42 - Typical application of IRU3146. 5V to 2.5V and 3.3V to 1.8V inputs and two independent outputs.
28
www.irf.com
Rev. 1.1 6/25/04
IRU3146
(F) TSSOP Package 28-Pin
A L Q R1 1.0 DIA B C R E M O D DETAIL A P N
F
PIN NUMBER 1
G J K H
DETAIL A
SYMBOL DESIG A B C D E F G H J K L M N O P Q R R1
MIN 4.30 0.19
28-PIN MAX NOM 0.65 BSC 4.40 6.40 BSC --1.00 1.00 9.70 --0.90 --12 REF 12 REF --1.00 REF 0.60 0.20 ----4.50 0.30
9.60 --0.85 0.05
9.80 1.10 0.95 0.15
0 0.50 0.09 0.09
8 0.75 -----
NOTE: ALL MEASUREMENTS ARE IN MILLIMETERS.
Rev. 1.1 6/25/04
www.irf.com
29
IRU3146
PACKAGE SHIPMENT METHOD
PKG DESIG F PACKAGE DESCRIPTION TSSOP PIN COUNT 28 PARTS PER TUBE 50 PARTS PER REEL 2500 T&R Orientation Fig A
1
1
1
Feed Direction Figure A
This product has been designed and qualified for the Industrial market.
IR WORLD HEADQUARTERS: 233 Kansas St., El Segundo, California 90245, USA Tel: (310) 252-7105 TAC Fax: (310) 252-7903 Visit us at www.irf.com for sales contact information Data and specifications subject to change without notice. 02/01
30
www.irf.com
Rev. 1.1 6/25/04

▲Up To Search▲

Price & Availability of IRU3146

	To Download IRU3146 Datasheet File
If you can't view the Datasheet, Please click here to try to view without PDF Reader .