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NX2155H
SINGLE POWER SUPPLY SYNCHRONOUS PWM CONTROLLER
ADVANCED DATA SHEET Pb Free Product
DESCRIPTION
The NX2155H controller IC is a single input supply synchronous Buck controller IC designed for step down DC to DC converter applications. NX2155H is optimized to convert bus voltages from 8V to 22V to output as low as 0.8V voltage. An internal regulator converts bus voltage to 5V, which provides voltage supply to internal logic and driver circuit. The NX2155H can operates at programmable frequency of 2MHz and employs loss-less current limiting by sensing the Rdson of synchronous MOSFET followed by hiccup feature.Feedback under voltage triggers Hiccup. Other features of the device are: Internal schottky diode, thermal shutdown, 5V gate drive, adaptive deadband control, internal digital soft start, 5VREG undervoltage lock out and Shutdown capability via the comp pin.
FEATURES
n Single supply voltage from 8V to 22V n Internal 5V regulator n Programmable operational frequency of 2MHz n Internal Digital Soft Start Function n Less than 50 nS adaptive deadband n Current limit triggers hiccup by sensing Rdson of Synchronous MOSFET n Pb-free and RoHS compliant
APPLICATIONS
n n n n LCD TV Graphic Card on board converters Memory Vddq Supply in mother board applications On board DC to DC such as 12V to 3.3V, 2.5V or 1.8V n Hard Disk Drive n Set Top Box
TYPICAL APPLICATION
10u 6 VIN 0.1u 5 4.7u 4.22k 5VREG BST 3 0.1u M1 AO6800 1u SW 1 OCP 10 LDRV 4 180p FB GND(PAD) 1n 15k 9 9.53k 6k 300 49.9k
VIN +12V
NX2155H
HDRV 2
VOUT +5V@2A
2 x (10uF,10V,X5R)
7 RT
8 COMP
10p
Figure1 - Typical application of 2155H
ORDERING INFORMATION
Device Temperature Package Package Marking Pb-Free NX2155HCUPTR 0 to 70o C MSOP-EP-10L NX155HXXX Yes Note: XXX is date code. For example, 841 means that this NX2155H is packaged in the 41th week of 2008
Rev.1.1 04/16/09
1
NX2155H
ABSOLUTE MAXIMUM RATINGS(NOTE1)
VCC to GND & BST to SW voltage ................... 6.5V BST to GND Voltage ...................................... 30V VIN to GND Voltage ........................................ 25V SW to GND .................................................... -2V to 35V All other pins .................................................. -0.3V to 6.5V Storage Temperature Range ............................. -65oC to 150oC Operating Junction Temperature Range ............. -40oC to 125oC NOTE1: Stresses above those listed in "ABSOLUTE MAXIMUM RATINGS", may cause permanent damage to the device. This is a stress only rating and operation of the device at these or any other conditions above those indicated in the operational sections of this specification is not implied.
PACKAGE INFORMATION
10-LEAD PLASTIC MSOP-EP
JA 46o C/W
SW 1 HDRV 2 BST 3 LDRV 4 5VREG 5 GND (PAD) 10 OCP 9 FB 8 COMP 7 RT 6 VIN
ELECTRICAL SPECIFICATIONS
Unless otherwise specified, these specifications apply over Vin = 12V, and T A = 0 to 70oC. Followings are bypass capacitors:CVIN=1uF, C5VREG=4.7uF, all X5R ceramic capacitors. Typical values refer to T A = 25oC. Low duty cycle pulse testing is used which keeps junction and case temperatures equal to the ambient temperature.
PARAMETER Reference Voltage Ref Voltage Ref Voltage line regulation 5VREG 5VREG Voltage range 5VREG UVLO 5VREG UVLO Hysteresis 5VREG Line Regulation 5VREG Max Current Supply Voltage(Vin) Vin Voltage Range Input Voltage Current(Static) Input Voltage Current (Dynamic) SYM VREF Vin=8V to 22V 4.75 5V REG rising VIN =9V to 22V 20 Vin No switching Switching with HDRV and LDRV open @2.2MHz 8 3.7 5.4 Test Condition Min 0.784 TYP 0.8 0.4 5 3.9 0.2 10 50 5.25 4.4 20 MAX 0.816 Units V % V V V mV mA V mA mA
4.8 8
22 6.5 11
Rev.1.1 04/16/09
2
NX2155H
PARAMET ER Vin UVLO V in-Threshold V in-Hysteresis SS Soft Start time Oscillator (Rt) Frequency Ramp-Amplitude Voltage Max Duty Cycle Min Controlable On Time Error Amplifiers T ransconductance Input Bias Current Comp SD Threshold FBUVL O Feedback UVLO threshold High Side Driver(C L=2200pF) Output Impedance , Sourcing Output Impedance , Sinking Rise Time Fall Tim e Deadband Time Low Side Driver (C L=2200pF) Output Impedance, Sourcing Current Output Impedance, Sinking Rise Time Fall Tim e Deadband Time OCP OCP current Over temperature T hreshold Hysteresis Internal Schottky Diode Forward voltage drop SYM V in_UVLO V in_Hyst Tss FS V RAMP FS=2.2MHz Test Condition Vin Rising Vin Falling FS=2.2MHz Rt=4.22k 1.4 62 Min 6 TYP 6.5 0.6 400 2250 1.5 71 1.9 80 150 1500 Ib 0.24 0.54 Rsource(Hdrv) R sink(Hdrv) THdrv(Rise) THdrv(Fall) Tdead(L to H) Rsource (Ldrv) I=200mA I=200mA 2000 10 0.3 0.6 1.9 1.7 14 17 30 2500 0.36 0.66 MAX 7.5 Units V V uS kHz V % nS umho nA V V ohm ohm ns ns ns
Ldrv going Low to Hdrv going High, 10%-10% I=200mA
21
39
1.9 1 13 12 10
ohm ohm ns ns ns
R sink (Ldrv) I=200mA TLdrv(Rise) TLdrv(Fall) Tdead(H to SW going Low to Ldrv L) going High, 10% to 10%
7
13
30
37 150 20
45
uA
o o
C C
forward current=20mA
350
500
mV
Rev.1.1 04/16/09
3
NX2155H
PIN DESCRIPTIONS
PIN # 5 PIN SYMBOL 5VREG PIN DESCRIPTION An internal 5V regulator provides supply voltage for the low side fet driver, BST and internal logic circuit. A high frequency 4.7uF X5R ceramic capacitor must be connected from this pin to the GND pin as close as possible. Voltage supply for the internal 5V regulator. A high freuqncy 0.1uF ceramic capacitor must be connected from this pin to GND. This pin is the error amplifier inverting input. This pin is also connected to the output UVLO comparator. When this pin falls below threshold, both HDRV and LDRV outputs are in hiccup. This pin is the output of the error amplifier and together with FB pin is used to compensate the voltage control feedback loop. This pin is also used as a shut down pin. When this pin is pulled below 0.3V, both drivers are turned off and internal soft start is reset. This pin supplies voltage to the high side driver. A high frequency ceramic capacitor of 0.1 to 1 uF must be connected from this pin to SW pin. This pin is connected to the drain of the external low side MOSFET and is the input of the over current protection(OCP) comparator. An internal current source is flown to the external resistor which sets the OCP voltage across the Rdson of the low side MOSFET. Current limit point is this voltage divided by the Rdson. This pin is connected to the source of the high side MOSFET and provides return path for the high side driver. High side MOSFET gate driver. Ground pin. Low side MOSFET gate driver. Oscillator's frequency can be set by using an external resistor from this pin to GND.
6
VIN
9
FB
8
COMP
3
BST
10
OCP
1
SW
2 PAD 4 7
HDRV GND LDRV RT
Rev.1.1 04/16/09
4
NX2155H
BLOCK DIAGRAM
VIN 5VREG
5V Regulator
UVLO Bias Generator 1.25V 0.8V UVLO POR START COMP 0.3V SW RT START 0.8V OSC Digital start Up ramp S R FB 0.6V CLAMP COMP START GND VCC Q Thermal Shutdown Hiccup Logic SS_done 0.6V 1.3V CLAMP FB LDRV OC OVP Latch PWM Control Logic VCC BST
HDRV
OCP
START
Figure 2 - Simplified block diagram of the NX2155H
Rev.1.1 04/16/09
5
NX2155H
Demoboard Design(VIN=12V, VOUT= 5V/2A, FREUQNCY=2.2MHz)
sdfd
BUS C1 0.1u 6 VIN CIN2 10uF,16V BST 3 CIN1 0.1uF
5 C2 4.7u
VCC
HDRV
2
C3 0.1u R8 0
4 HDRV 3 2
M1B AO6800
U1
SW 7 R1 4.22k RT OCP 1 R2 6k
L1 SW BRL3225T1R0M 10 OUT VOUT
NX2155H/MSOP-EP10
M1A AO6800
R7 10
COUT1 10uF,16V
COUT2 10uF,16V
LDRV
4
LDRV 1 C7 470p GND
6
R3 300
R4 49.9k GND
5
C4 180p
FB
9 R6 15k C5 1n C6 10p R5 9.53k
COMP GNDPAD
8
* R7 and C7 are optional.
11
Figure 3 - Simplified demoboard schematic of NX2155H
Rev.1.1 04/16/09
6
NX2155H
Bill of Materials
Item 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 Quantity 3 1 1 1 1 1 1 2 1 1 1 1 1 1 1 1 1 1 1 Reference C1,C3,CIN1 C2 C4 C5 C6 C7 CIN2 COUT1,COUT2 L1 M1 R1 R2 R3 R4 R5 R6 R7 R8 U1 Part 0.1u 4.7uF,6.3V,X5R 180p 1n 10p 470p 10uF,16V,X5R 10uF,10V,X5R BRL3225T1R0M AO6800 4.22k 6k 300 49.9k 9.53k 15k 10 0 NX2155H/MSOP-EP10 Manufacturer
TAIYO YUDEN AOS
NEXSEM INC.
Rev.1.1 04/16/09
7
NX2155H
Demoboard Waveforms
Fig.4 Output ripple(CH1 VOUT AC 50mV/DIV, CH2 SW 10V/DIV, CH4 OUTPUT CURRENT 2A/DIV)
Fig.5 Startup( CH1 VOUT 2V/DIV)
Fig.6 OCP protection during output short(CH1 VOUT 2V/DIV, CH4 OUTPUT CURRENT 5A/DIV)
100.00% 90.00% 80.00% 70.00% Efficiency (%) 60.00% 50.00% 40.00% 30.00% 20.00% 10.00% 0.00% 0 500 1000 1500 2000 2500 Iout (mA)
Fig.7 Output dynamic response(CH1 VOUT AC 200mV/DIV, CH4 OUTPUT CURRENT 500mA/DIV)
Fig.8 Output efficiency
Rev.1.1 04/16/09
8
NX2155H
Demoboard Layout
Figure 9 Top layer
Figure 10 Ground layer
Rev.1.1 04/16/09
9
NX2155H
Figure 11 Power layer
Figure 12 Bottom layer
Rev.1.1 04/16/09
10
NX2155H
Demoboard Design( (VIN=12V, VOUT= 5V/10A, FREUQNCY=400kHz)
BUS BUS C18 100u/16v 1
C3 0.1u
VIN
6
BST
3 C9 22u/25V C10 22u/25V
5 C5 4.7u
VCC
C4 0.1u
8 7 6 5 9
U1
7 R3 30k RT
M1 HDRV 2 HDRV 4
BSC119N03S
SW VOUT 2 VOUT
1 2 3
N X 2 1 5 5 /M S O P -EP10
SW
1
SW
1
L1
DO5010H-222MLD C14 C15 47uF/6.3V/X5R 47uF/6.3V/X5R C19 47uF/6.3V/X5R GND 8 7 6 5 9 3k M2 BSC029N025S R17 2.15 LDRV 4 1 2 3
OCP
10
R1
LDRV
4
C13 1000p
R9 100k FB 9 R7 30k C21 1n C22 33p R10 19.1k R8 C23
750
220p
COMP GNDPAD
8
11
Figure 13 - Simplified demoboard schematic of NX2155H
Rev.1.1 04/16/09
11
NX2155H
Bill of Materials
Item 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 Quantity 2 1 2 1 3 1 1 1 1 1 1 1 1 2 1 1 1 1 1 Reference C3,C4 C5 C9,C10 C13 C14,C15,C19 C18 C21 C22 C23 L1 M1 M2 R1 R3,R7 R8 R9 R10 R17 U1 Part 0.1u 4.7u 22u/25V/X5R 1000p 47uF/6.3V/X5R 100u/16v 1n 33p 220p DO5010H-222MLD BSC119N03S BSC029N025S 3k 30k 750 100k 19.1k 2.15 NX2155/MSOP-EP10 Manufacturer
COILCRAFT INFINEON INFINEON
NEXSEM INC.
Rev.1.1 04/16/09
12
NX2155H
Demoboard Waveforms
Fig.14 Output ripple(CH1 SW 10V/DIV, CH2 VOUT AC 50mV/DIV, CH4 INDUCTOR CURRENT 5A/DIV)
Fig.15 Startup( CH1 VOUT 2V/DIV, CH4 INDUCTOR CURRENT 5A/DIV)
Fig.16 OCP protection during output short(CH2 VOUT 2V/DIV, CH4 OUTPUT CURRENT 5A/DIV)
Fig.17 Output dynamic response(CH2 VOUT AC 200mV/DIV, CH4 OUTPUT CURRENT 5A/DIV)
Fig.18 Output efficiency
Rev.1.1 04/16/09
13
NX2155H
APPLICATION INFORMATION
Symbol Used In Application Information:
VIN VOUT IOUT FS - Input voltage - Output voltage - Output current - Working frequency
Compensator Design
Due to the double pole generated by LC filter of the power stage, the power system has 180o phase shift , and therefore, is unstable by itself. In order to achieve accurate output voltage and fast transient response, compensator is employed to provide highest possible bandwidth and enough phase margin.Ideally,the Bode plot of the closed loop system has crossover frequency between1/10 and 1/5 of the switching frequency, phase margin greater than 50o and the gain crossing 0dB with 20dB/decade. Power stage output capacitors usually decide the compensator type. If electrolytic capacitors are chosen as output capacitors, type II compensator can be used to compensate the system, because the zero caused by output capacitor ESR is lower than crossover frequency. Otherwise type III compensator should be chosen.
DVRIPPLE - Output voltage ripple DIRIPPLE - Inductor current ripple
Output Inductor Selection
The selection of inductor value is based on inductor ripple current, power rating, working frequency and efficiency. Larger inductor value normally means smaller ripple current. However if the inductance is chosen too large, it brings slow response and lower efficiency. Usually the ripple current ranges from 20% to 40% of the output current. This is a design freedom which can be decided by design engineer according to various application requirements. The inductor value can be calculated by using the following equations:
A. Type III compensator design
For low ESR output capacitors, typically such as Sanyo oscap and poscap, the frequency of ESR zero caused by output capacitors is higher than the cross-
V -V V 1 L OUT = IN OUT x OUT x VIN FS IRIPPLE IRIPPLE =k x IOUTPUT
where k is between 0.2 to 0.4.
...(1)
over frequency. In this case, it is necessary to compensate the system with type III compensator. The following figures and equations show how to realize the type III compensator by transconductance amplifier.
Output Capacitor Selection
Output capacitor is basically decided by the amount of the output voltage ripple allowed during steady state(DC) load condition as well as specification for the load transient. The optimum design may require a couple of iterations to satisfy both condition. The amount of voltage ripple during the DC load condition is determined by equation(2).
FZ1 = FZ2 = FP1 = FP2 =
1 2 x x R 4 x C2 1 2 x x (R 2 + R 3 ) x C 3 1 2 x x R 3 x C3 1 2 x x R4 x C1 x C 2 C1 + C 2
...(3) ...(4) ...(5) ...(6)
VRIPPLE = ESR x IRIPPLE
IRIPPLE + 8 x FS x COUT ...(2)
Where ESR is the output capacitors' equivalent series resistance,COUT is the value of output capacitors. Typically when ceramic capacitors are selected as output capacitors, DC ripple spec is easy to be met, but mutiple ceramic capacitors are required at the output to meet transient requirement.
where FZ1,FZ2,FP1 and FP2 are poles and zeros in the compensator. Their locations are shown in figure 20. The transfer function of type III compensator for transconductance amplifier is given by:
Ve 1 - gm x Z f = VOUT 1 + gm x Zin + Z in / R1
Rev.1.1 04/16/09
14
NX2155H
For the voltage amplifier, the transfer function of compensator is
B. Type II compensator design
Type II compensator can be realized by simple RC circuit without feedback as shown in figure 22. R3 and C1 introduce a zero to cancel the double pole effect. C2 introduces a pole to suppress the switching noise. The following equations show the compensator pole zero location and constant gain.
Ve -Z f = VOUT Zin
To achieve the same effect as voltage amplifier, the compensator of transconductance amplifier must
satsf t scondion:R4>>2/gm. And it would be desiri y hi t i
able if R 1||R2||R3>>1/gm can be met at the same time.
Gain=gm x Fz =
R1 x R3 R1 +R 2
... (7) ... (8) ... (9)
Zin R3
Vout
Zf C1 C2 Fb gm Ve R4
1 2 x x R 3 x C1 1 2 x x R3 x C2
Fp
R2 C3 R1
For this type of compensator, FO has to satisfy FLCVref
Gain(db)
power stage 40dB/decade loop gain 20dB/decade
Figure 19 - Type III compensator using transconductance amplifier
power stage Gain(db)
FLC
40dB/decade
compensator Gain
loop gain 20dB/decade
FZ FLC FESR
FESR
FO FP
FO
compensator
Figure 21 - Bode plot of Type II compensator
FZ1 FZ2
FP2 FP1 F S
Figure 20 - Bode plot of Type III compensator
Rev.1.1 04/16/09
15
NX2155H
Over Current Protection
Vout R2 Fb gm R1 Vref Ve R3 C2 C1
Over current protection is achieved by sensing current through the low side MOSFET. A typical internal current source of 37uA flowing through an external resistor connected from OCP pin to SW node sets the over current protection threshold. When synchronous FET is on, the voltage at node SW is given as
VSW =-IL x RDSON
The voltage at pin OCP is given as
IOCP x ROCP +VSW
When the voltage is below zero, the over current Figure 22 - Type II compensator with transconductance amplifier
I OCP
occurs.
vbus
Output Voltage Calculation
Output voltage is set by reference voltage and external voltage divider. The reference voltage is fixed at 0.8V. The divider consists of two ratioed resistors so that the output voltage applied at the Fb pin is 0.8V when the output voltage is at the desired value. The following equation and picture show the relationship between
OCP comparator
OCP R OCP
SW
Figure 24 - Over current protection The over current limit can be set by the following equation
VOUT , VREF and voltage divider. .
R 1= R 2 x VR E F V O U T -V R E F
...(10)
ISET =
IOCP x ROCP K x RDSON
where R2 is part of the compensator, and the value of R1 value can be set by voltage divider. See compensator design for R1 and R2 selection.
Frequency Selection
The frequency can be set by external Rt resistor. The relationship between frequency and RT pin is shown as follows.
NX2155H Frequency vs Rt
Vout R2 Fb R1 Vref Voltage divider
Figure 23 - Voltage divider
2500 2000 Frequency(kHz) 1500
1000 500 0 3 8 13 18 23 Rt(kohm) 28 33 38
Figure 25 - Frequency versus Rt resistor
Rev.1.1 04/16/09
16
NX2155H
MSOP 10 PIN WITH EXPOSED PAD OUTLINE DIMENSIONS
NOTE: ALL DIMENSIONS ARE DISPLAYED IN INCHES.
Rev.1.1 04/16/09
17

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