NX9511B
9A SYNCHRONOUS BUCK SWITCHING REGULATORWITH 1MHz
OPERATION FREQUENCY
PRELIMINARY DATA SHEET
Pb Free Product
DESCRIPTION
The NX9511B is synchronous buck switching converter
in multi chip module designed for step down DC to DC
converter applications. They are optimized to convert
bus voltages from 2V to 25V to as low as 0.8V output
voltage. The output current can be up to 9A. The NX9511B
offer an Enable pin that can be used to program the
converter's start up. NX9511B operates at fixed internal
frequency of 1MHz and employ loss-less current limit-
ing protection by sensing the Rdson of synchronous
MOSFET followed by latch out feature. Feedback under
voltage triggers Hiccup.
Other features are: Internal digital soft start; Vcc
undervoltage lock out and shutdown capability via the
enable pin or comp pin. NX9511B is available in 5x5 MCM
package.
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FEATURES
Switching Controller and MOSFETs in one package
Bus voltage operation from 2V to 25V
Fixed 1MHz
Internal Digital Soft Start Function
Output current up to 9A
Enable pin to program BUS UVLO
Programmable current limit triggers latch out by
sensing Rdson of Synchronous MOSFET
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No negative spike at Vout during startup and
shutdown
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Pb-free and RoHS compliant
APPLICATIONS
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Low Profile On board DC to DC Application
Graphic Card on board converters
Memory Vddq Supply
ADSL Modem
TYPICAL APPLICATION
Vin1
+12V
Vin2
+5V
D1
2*22uF
VCC
1uF
BAT54A
EN
COMP
820p
15p
20k
NX9511B
BST
S1
D2
SW
OCP
HG
HDRV
S2
0.1uF
1uH
Vout
+1.2V,9A
6x (22uF,X5R)
5k
200
FB
LG
AGND
40k
390p
16k
Figure 1 - Typical application of 9511B
ORDERING INFORMATION
Device
NX9511BCMTR
Temperature
0 to 70
o
C
Package
5X5 MCM-32L
Frequency
1MHz
Pb-Free
Yes
Rev.1.5
01/16/08
1
NX9511B
ABSOLUTE MAXIMUM RATINGS
VCC to GND & BST to SW voltage .................... -0.3V to 6.5V
D1 to GND ........................................................ 25V
BST to GND Voltage ........................................ -0.3V to 35V
D2,S1 to GND .................................................. -2V to 35V
All other pins .................................................... -0.3V to VCC+0.3V or 6.5V
Storage Temperature Range ............................... -65
o
C to 150
o
C
Operating Junction Temperature Range ............... -40
o
C to 125
o
C
ESD Susceptibility ........................................... 2kV
Power Dissipation ............................................. TBD
Output Current ...................................................TBD
CAUTION: 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
32-LEAD PLASTIC MCM 5 x 5
AGND
HDRV
BST
D1
32 31 30 29 28 27 26 25
S1
S1
S1
D1
D2
1
2
3
4
5
D2
(PAD3)
D1
(PAD2)
AGND
(PAD1)
24 OCP
23 COMP
22 FB
21 AGND
20 EN
19 D2
18 VCC
17 NC
9 10 11 12 13 14 15 16
S2
S2
NC
LG
S2
S2
S2
S2
D2 6
D2 7
D2
8
D1
SW
HG
D1
Rev.1.5
01/16/08
2
NX9511B
ELECTRICAL SPECIFICATIONS
Unless otherwise specified, these specifications apply over Vcc = 5V, V
IN
= 12V and T
A
= 0 to 70
o
C. Typical values
refer to T
A
= 25
o
C. 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
Supply Voltage(Vcc)
V
CC
Voltage Range
V
CC
Supply Current (Static)
Supply Voltage(V
BST
)
V
BST
Supply Current (Static)
VCC, V
BST
Supply Current
(Dynamic)
Under Voltage Lockout
V
CC
-Threshold
V
CC
-Hysteresis
Oscillator
Frequency
Ramp-Amplitude Voltage
Max Duty Cycle
Min Duty Cycle
Error Amplifiers
Transconductance
Input Bias Current
EN & SS
Soft Start time
Enable HI Threshold
Enable Hysterises
Ouput Stage
High Side MOSFET R
DSON
Low Side MOSFET R
DSON
Output Current
OCP Adjust
OCP current
FB Under Voltage Protection
FB Under Voltage Threshold
SYM
V
REF
Test Condition
Min
TYP
0.8
0.2
MAX
Units
V
%
V
CC
I
CC
(Static) Outputs not switching
I
BST
(Static) Outputs not switching
I(Dynamic)
4.5
5
3
0.2
15
5.5
V
mA
mA
mA
V
CC
_UVLO V
CC
Rising
V
CC
_Hyst
F
S
V
RAMP
V
CC
Falling
4
0.2
1
1.5
75
0
2000
10
2
1.25
150
17
17
9
40
0.48
V
V
MHz
V
%
%
umho
nA
mS
V
mV
ohm
ohm
A
uA
V
Ib
Tss
Rev.1.5
01/16/08
3
NX9511B
PIN DESCRIPTIONS
PIN #
1-3
5-8,19
9-14
15,17
16
18
PIN SYMBOL
PIN DESCRIPTION
S1
Bus input which is connected to high side MOSFET's drain.
D2
S2
NC
LG
VCC
Low side gate driver output for monitoring.
Power supply voltage. A high freq 1uF ceramic capacitor is placed as close as pos-
sible to and connected to this pin and ground pin. The maximum rating of this pin is
5V.
External enable signal input for the controller.
This pin is the error amplifier inverting input. It is connected via resistor divider to the
output of the switching regulator to set the output DC voltage. When FB pin voltage is
lower than 0.6V, hiccup circuit starts to recycle the soft start circuit after 2048 switching
cycles.
This pin is the output of error amplifier and is used to compensate the voltage control
feedback loop. This pin can also be used to perform a shutdown if pulled lower than
0.3V.
This pin is connected to the drain of the external low side MOSFET via resistor and
is the input of the over current protection(OCP) comparator. An internal current source
40uA 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 Rds-on.
Once this threshold is reached the Hdrv and Ldrv pins are latched out.
Ground pin.
SW is the controller pin out which needs to be connected to S1and D2 and provides
return path for the high side driver.
High side gate driver output which needs to be connected high side MOSFET gate
HG.
This pin supplies voltage to high side FET driver. A high freq 0.1uF ceramic capacitor
is placed as close as possible to and connected to these pins and respected SW
pins.
Analog ground.
High side MOSFET gate which needs to be connected to high side gate driver output
HDRV.
Drain of High side MOSFET.
Drain of low side MOSFET.
Source of low side MOSFET and need to be connected to power ground.
20
22
EN
FB
23
COMP
24
OCP
25
SW
26
HDRV
27
BST
21,28
29
AGND
HG
30-32,4
D1
Rev.1.5
01/16/08
4
NX9511B
BLOCK DIAGRAM
BST
HDRV
HG
D1
VCC
FB
0.6V
Bias
Generator
1.25V
0.8V
UVLO
POR
START
Hiccup Logic
OC
EN
1.25
/1.15
OC
START 0.8V
OSC
Digital
start Up
ramp
S
R
FB
S2
COMP
START
AGND
0.6V
CLAMP
1.3V
CLAMP
Latch Out
OCP
comparator
40uA
LG
OCP
Q
OC
PWM
Control
Logic
VCC
SW
D2
S1
Figure 2 - Simplified block diagram of the NX9511B
Rev.1.5
01/16/08
5
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