nx2116 Microsemi Corporation, nx2116 Datasheet

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nx2116

Manufacturer Part Number
nx2116
Description
Synchronous Pwm Controller With Current Limit, Power Good & Over Voltage
Manufacturer
Microsemi Corporation
Datasheet
Rev. 3.0
03/14/06
The NX2116/2117 family of products are synchronous
Buck controller IC 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 NX2116 and 2117 offer an Enable pin that
can be used to program the converter's start up voltage
using an external divider from bus voltage. These prod-
ucts operate at fixed internal frequency of 300kHz, ex-
cept that NX2116A operates at 600kHz and 2116B at
1MHz frequency. These products employ loss-less cur-
rent limiting protection by sensing the Rdson of syn-
chronous MOSFET followed by latch out feature. Feed-
back under voltage triggers Hiccup.
Other features are; 5V gate drive, Power good indica-
tor, Adaptive deadband control, Internal digital soft start;
Vcc undervoltage lock out and shutdown capability via
the enable pin or comp pin.
ON
OFF
NX2116CMTR
NX2116ACMTR
NX2117CUTR
NX2117ACUTR
NX2116BCMTR
R8
10k
Device
R7
10k
Vin2
+12V
+5V
Vin1
2N3904
39uF
C3
CURRENT LIMIT, POWER GOOD & OVER VOLTAGE
68k
Temperature
12.4k
R5
R6
DESCRIPTION
0 to 70
0 to 70
0 to 70
0 to 70
0 to 70
33pF
C1
1uF
C4
17.4k
R3
10
C2
1.5nF
16k
R4
R2
Figure 1 - Typical application of 2116
SYNCHRONOUS PWM CONTROLLER WITH
o
o
o
o
o
C
C
C
C
C
11
6
8
7
Comp
EN
Gnd
Fb
Vcc
4
NX2116/2116A/2116B/2117/2117A
MLPD-10L
MLPD-10L
MLPD-10L
MSOP-10L
MSOP-10L
Package
2.61k
L2 1uH
R9
R1
Pgood
BST
1
Hdrv
OCP
20k
n
n
n Fixed 300kHz, 600kHz and 1MHz for NX2116 and
n Internal Digital Soft Start Function
n Less than 50 nS adaptive deadband
n Enable pin to program BUS UVLO for NX2116/2117
n
n
n
n
n
n
Ldrv
SW
1nF
C8
D1
MBR0530T1
300kHz, 600kHz for NX2117 family.
10
2
Bus voltage operation from 2V to 25V
Power Good indicator available in NX2116
Programmable current limit triggers latch out by
sensing Rdson of
Synchronous MOSFET
No negative spike at Vout during startup and
shutdown
Graphic Card on board converters
Memory Vddq Supply
On board DC to DC such as 2V to 3.3V, 2.5V or
1.8V
ADSL Modem
3
5
9
R10
R11
1k
3.7k
ORDERING INFORMATION
C7
0.1uF
+5V
TYPICAL APPLICATION
Frequency
300kHz
600kHz
1MHz
300kHz
600kHz
M1
M2
C5
1uF
L1 1uH
PRELIMINARY DATA SHEET
APPLICATIONS
270uF,18mohm
Cin
Co
2x (220uF,12mohm)
Pb Free Product
Pb-Free
FEATURES
Yes
Yes
Yes
Yes
Yes
Vout
+1.8V,9A
1

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nx2116 Summary of contents

Page 1

... Buck controller IC designed for step down converter applications. They are optimized to convert bus voltages from 2V to 25V to as low as 0.8V output voltage. The NX2116 and 2117 offer an Enable pin that can be used to program the converter's start up voltage using an external divider from bus voltage. These prod- ...

Page 2

... V Supply Current (Static Supply Current CC (Dynamic) (Dynamic) Supply Voltage(V ) BST V Supply Current (Static) I BST V Supply Current BST (Dynamic) (Dynamic) Rev. 3.0 03/14/06 NX2116/2116A/2116B/2117/2117A 150 125 C NX2117/2117A 10-LEAD PLASTIC MSOP JA BST 1 HDrv 2 GND 3 4 LDrv 5 VCC SYM Test Condition ...

Page 3

... Rev. 3.0 03/14/06 NX2116/2116A/2116B/2117/2117A SYM Test Condition _UVLO V Rising _Hyst V Falling 2116, 2117 S 2116A,2117A 2116B V RAMP Ib Tss NX2116,NX2117 NX2116A, NX2117A NX2116B (Hdrv) I=200mA source (Hdrv) I=200mA sink V -V =4.5V BST =4.5V BST SW Ldrv going Low to Hdrv going H) High, 10%-10% (Ldrv) I=200mA source R (Ldrv) ...

Page 4

... An external low cost Transistor can be connected to this pin for external enable control. This pin is the output of error amplifier and is used to compensate the voltage control COMP feedback loop. This pin can also be used to perform a shutdown if pulled lower than 0.3V. Rev. 3.0 03/14/06 NX2116/2116A/2116B/2117/2117A PIN DESCRIPTION 4 ...

Page 5

... BLOCK DIAGRAM VCC 1.25V Bias Generator 0.8V EN 1.25/1.15 START 0.8V OSC Digital ramp start Up FB COMP START GND Figure 2 - Simplified block diagram of the NX2116 Rev. 3.0 03/14/06 NX2116/2116A/2116B/2117/2117A FB 0.6V UVLO POR START OC PWM 0.6V CLAMP 1.3V CLAMP Latch Out Hiccup Logic OC BST HDRV SW Control Logic VCC LDRV OC 40uA ...

Page 6

... Input voltage Output voltage OUT I - Output current OUT DV - Output voltage ripple RIPPLE F - Working frequency Inductor current ripple RIPPLE Design Example The following is typical application for NX2116A, the schematic is figure 12V IN V =1.8V OUT F =600kHz S I =9A OUT DV <=20mV RIPPLE DV < ...

Page 7

... The above equation shows that if the selected out- put inductor is smaller than the critical inductance, the voltage droop or overshoot is only dependent on the ESR Rev. 3.0 03/14/06 NX2116/2116A/2116B/2117/2117A of output capacitor. For low frequency capacitor such as electrolytic capacitor, the product of ESR and ca- pacitance is high and transient spec is dependent on the ESR of capacitor. ...

Page 8

... In this case necessary to compen- sate the system with type III compensator. The follow- ing figures and equations show how to realize the type III compensator by transconductance amplifier. Rev. 3.0 03/14/06 NX2116/2116A/2116B/2117/2117A ...

Page 9

... ESR C OUT 440uF 60.3kHz 2. Set R equal to 20k . 20k 0.8V 2 REF 1.8V-0.8V OUT REF Rev. 3.0 03/14/06 NX2116/2116A/2116B/2117/2117A Choose R 3. Set zero F 4. Calculate R frequency at 1/10~ 1/5 of the switching frequency. Set F =50kHz =916pF 1.5V = 12V =17.2k Choose C 5. Calculate C F double pole by equation (11). ...

Page 10

... ESR OUT OUT 1 2 1uH 3000uF 2.9kHz 1 F ESR 2 ESR C OUT 1 2 6.5m 3000uF 8.2kHz Rev. 3.0 03/14/06 NX2116/2116A/2116B/2117/2117A 2. Set OUT Choose R 3. Set zero F 4. Calculate =3.5nF Choose C 5. Calculate 5. Choose R 6. Calculate R ...

Page 11

... ESR Figure 6 - Bode plot of Type II compensator Rev. 3.0 03/14/06 NX2116/2116A/2116B/2117/2117A Vout R2 and Figure 7 - Type II compensator with For this type of compensator, F ... (17) F <F <<F LC ESR The following is parameters for type II compensa- tor design. Input voltage is 12V, output voltage is 1.8V, ...

Page 12

... where R is part of the compensator, and the value value can be set by voltage divider. 1 See compensator design for R Rev. 3.0 03/14/06 NX2116/2116A/2116B/2117/2117A Vout R2 V OUT V REF R1 1 2.0mA/V Figure 8 - Voltage divider Input Capacitor Selection Z Input capacitors are usually a mix of high frequency ceramic capacitors and bulk capacitors ...

Page 13

... Figure 9 - Enable and Shut down the NX2116 with Enable pin. The start up of NX2116 can be programmed through resistor divider at Enable pin. For example, if the input bus voltage is12V and we want NX2116 starts when Vbus . ..(21) is above 9V. We can select using the following equa- ...

Page 14

... The goal is to localize the high current path to a separate loop that does not interfere with the more sen- sitive analog control function. These two grounds must be connected together on the PC board layout at a single point. Rev. 3.0 03/14/06 NX2116/2116A/2116B/2117/2117A vbus SW OCP 3.656k 14 ...

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