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PDF NCP5217A Data sheet ( Hoja de datos )
| Número de pieza | NCP5217A | |
| Descripción | Single Synchronous Step-Down Controller | |
| Fabricantes | ON Semiconductor | |
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NCP5217A
Single Synchronous
Step-Down Controller
The NCP5217A is a synchronous step−down controller for high
performance systems battery−power systems. The NCP5217A
includes a high efficiency PWM controller. A pin is provided to enable
or disable forced PWM mode of operation. An internal power good
voltage monitor tracks the SMPS output. NCP5217A also features
soft−start sequence, UVLO for VCC and switcher, overvoltage
protection, overcurrent protection, undervoltage protection and
thermal shutdown. The IC is packaged in QFN14.
Features
• 0.8% accuracy 0.8 V Reference
• 4.5 V to 27 V Battery/Adaptor Voltage Range
• Adjustable Output Voltage Range: 0.8 V to 3.3 V
• Selectable Power Saving Mode / Force PWM Mode
• Lossless Inductor Current Sensing
• Programmable Transient−Response−Enhancement (TRE) Control
• Programmable Adaptive Voltage Positioning (AVP)
• Input Supply Feedforward Control
• Internal Soft−Start
• Integrated Output Discharge (Soft−Stop)
• Build−in Adaptive Gate Drivers
• PGOOD Indication
• Overvoltage, Undervoltage and Overcurrent Protections
• Thermal Shutdown
• QFN14 Package
• These Devices are Pb−Free and are RoHS Compliant
Typical Applications
• Notebook Application
• System Power
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MARKING
DIAGRAM
QFN14
CASE 485AL
N5217
ALYWG
G
A = Assembly Location
L = Wafer Lot
Y = Year
W = Work Week
G = Pb−Free Package
(Note: Microdot may be in either location)
EN_SKIP
1
BST
14
CS+ 2
CS−/Vo 3
COMP 4
FB 5
PGOOD 6
13 DH
12 SWN
11 IDRP/OCP
10 VCC
9 DL/TRESET
7
AGND
8
PGND
QFN14
(Top View)
ORDERING INFORMATION
Device
Package
Shipping†
NCP5217AMNTXG QFN14
(Pb−Free)
3000 /
Tape & Reel
†For information on tape and reel specifications,
including part orientation and tape sizes, please
refer to our Tape and Reel Packaging Specifications
Brochure, BRD8011/D.
© Semiconductor Components Industries, LLC, 2011
May, 2011 − Rev. 2
1
Publication Order Number:
NCP5217A/D
1 page  
NCP5217A
ELECTRICAL CHARACTERISTICS (VIN = 12 V, VCC = 5 V, TA = −40°C to 85°C, unless other noted)
Characteristics
Symbol
Test Conditions
Min
INTERNAL SOFT−START
Soft−Start Time
VOLTAGE ERROR AMPLIFIER
TSS
0.9
DC Gain
GAIN_VEA
(Note 2)
Unity Gain Bandwidth
BW_VEA
(Note 2)
Slew Rate
SR_VEA
COMP PIN TO GND = 100 pF (Note 2)
FB Bias Current
Ibias_FB
Output Voltage Swing
Vmax_EA
Isource_EA = 2 mA
3.3
Vmin_EA
Isink_EA = 2 mA
DIFFERENTIAL CURRENT SENSE AMPLIFIER
CS+ and CS− Common−mode
Input Signal Range
VCSCOM_MAX
Refer to AGND
Input Bias Current
CS_IIB
−100
Input Signal Range
CS_range
−70
Offset Current at IDRP
IDRP_offset
(CS+) − (CS−) = 0 V
−1.0
[(CS+) − (CS−)] to IDRP Gain
Current−Sense Bandwidth
IDRP_GAIN
(IDRP/((CS+) −
(CS−)))
BW_CS
(CS+) − (CS−) =
10 mV, V(IDRP) =
0.8 V
TA = 25°C
TA=−40°C to 85°C
At −3dB to DC Gain (Note 2)
0.475
0.425
Maximum IDRP Output Voltage
Minimum IDRP Output Voltage
IDRP_Max
IDRP_Min
(CS+) − (CS−) = 70 mV, Isource drops to
95% of the value when V(IDRP) = 0.8 V
2.5
IDRP Output current
I_IDRP
−1.0
OVERCURRENT PROTECTION SETTING
Overcurrent Threshold (OCTH)
Detection Current
I_OCSET
Sourced from OCP before soft−start,
Rocp = 16.7 kW is connected from OCP to
AGND or FB
21.6
Ratio of OC Threshold over
OCSET Voltage
K_OCSET
V((CS+) − (CS−)) / V_OCSET
(Note 2)
OCSET Voltage for Default
Fixed OC Threshold
VOCSET_DFT
Rocp v 2 kW is connected from OCP to
AGND or FB
OCSET Voltage for Adjustable
OC Threshold
VOCSET_ADJ Rocp = 8.3 ~ 25 kW is connected from OCP
to AGND or FB
200
OCSET Voltage for OC Disable VOCSET_DIS
Rocp w 35 kW is connected from OCP to
AGND or FB
720
Default Fixed OC Threshold
V_OCTH_DFT (CS+) – (CS−), Pin IDRP/OCP is shorted to
AGND or FB
35
Adjustable OC Threshold
V_OCTH
((CS+) − (CS−))
(CS+) – (CS−),
During OC threshold,
set a voltage at pin
OCP
VOCSET = 200 mV
VOCSET = 600 mV
15
52
GATE DRIVERS
DH Pull−HIGH Resistance
RH_DH
200 mA Source current
DH Pull−LOW Resistance
RL_DH
200 mA Sink current
DL Pull−HIGH Resistance
RH_DL
200 mA Source current
DL Pull−LOW Resistance
RL_DL
200 mA Sink current
2. Guaranteed by design, not tested in production.
Typ
1.1
88
15
2.5
3.5
0.15
0.525
20
0
24
0.1
40
20
60
2.5
1.5
2
0.75
Max Unit
1.3 ms
dB
MHz
V/ms
0.1 mA
V
0.3
3.5 V
100
70
1.0
0.575
0.625
nA
mV
mA
mA/mV
MHz
V
V
35 mA
26.4 mA
−
100 mV
600 mV
mV
45 mV
25 mV
68
W
W
W
W
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5
5 Page 
NCP5217A
Overcurrent Protection (OCP)
The NCP5217A protects power system if over current
event occurs. The current is continuously monitored by the
differential current sensing circuit. The current limit
threshold voltage VOCSET can be programmed by resistor
Rocset connecting at the IDRP/OCP pin. However, fixed
default VOCSET can be achieved if Rocset is less than 2 kW.
If the inductor current exceeds the current threshold
continuously, the top gate driver will be turned off cycle by
cycle. If it happens over consecutive 16 clock cycles time
(16 x 1/fSW), the device is latched off such that top and
bottom gate drivers are off. EN resets or power recycle the
device can exit the fault. The following diagram shows the
typical behavior of OCP.
Top to Bottom : SWN, Vo, PGOOD, Io
Figure 20. Overcurrent Protection
The NCP5217A uses lossless inductor current sensing for
acquiring current information. In addition, the threshold
OCP voltage can be programmed to some desired value by
setting the programming resistor Rocp.
Vo
Rt
Rb
FB
IDRP/OCP
L Rs1 Rocp
CS+
DCR Cs
Rs2 CS−
+
+− Vref IDRP
+
Gi
COMP
Vo
Rt
FB
Rb
Rocp
IDRP/OCP
L Rs1
CS+
DCR Cs
Rs2
CS−
Without AVP
+
+− Vref IDRP
+
Gi
COMP
With AVP
Figure 21. OCP Configurations
It should be noted that there are two configurations for
Rocp resistor. If Adaptor Voltage Position (AVP) is used, the
Rocp should be connected to FB pin. If AVP is not used, the
Rocp should be connected to ground. At the IDRP/OCP pin,
there is a constant current(24 mA typ.) flowing out during the
programming stage at system start up. This is used to sense
the voltage level which is developed by a resistor Rocp so as
to program the overcurrent detection threshold voltage. For
typical application, the Vocth is set as default value (40 mV
typ) by setting Rocp = 0 W, or directly short the IDRP/OCP
pin to ground. It has the benefit of saving one component at
application board. For other programming values of Vocth,
please refer to the electrical table of “Overcurrent Protection
Setting” section.
Guidelines for selecting OCP Trip Component
1. Choose the value of Rocp for Vocth selection.
(typical is 0 W for Vocth = 40 mV typical)
2. Define the DC value of OCP trip point (IOCP_DC)
that you want. The typical value is 1.5 to 1.8 times
of maximum loading current. For example, if
maximum loading is 10 A, then set OCP trip point
at 15 A to 18 A.
3. Calculate the inductor peak current (Ipk)which is
estimated by the equation:
Ipk
+
IOCP_DC
)
VO * (VIN *
2 * VIN * fSW
VO)
* LO
(eq. 4)
4. Check with inductor datasheet to find out the value
of inductor DC resistance DCR, then calculate the
RS1, RS2 dividing factor k based on the equation:
k
+
VOCth
Ipk * DCR
(eq. 5)
5. Select Cs value between 100 nF to 200 nF.
Typically, 100 nF will be used.
6. Calculate Rs1 value by the equation:
Rs1
+
k
*
L
DCR
*
Cs
7. Calculate Rs2 value by the equation:
(eq. 6)
Rs2
+
k * Rs1
1*k
(eq. 7)
8. Hence, all the current sense components Rs1, Rs2,
Cs have been found for target IOCP_DC.
9. If Rs2 is not used (open), set k = 1, at that
moment, the Ipk will be restricted by:
Ipk
+
VOCth
DCR
(eq. 8)
Overvoltage Protection (OVP)
When VFB voltage is above 115% (typical) of the nominal
VFB voltage for over 1.5 ms blanking time, an OV fault is set.
At that moment, the top gate drive is turned off and the
bottom gate drive is turned on until the VFB below lower
under voltage (UV) threshold and bottom gate drive is
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| Páginas | Total 16 Páginas | |
| PDF Descargar | [ Datasheet NCP5217A.PDF ] | |
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