|
|
PDF MAX5974C Data sheet ( Hoja de datos )
| Número de pieza | MAX5974C | |
| Descripción | Current-Mode PWM Controllers | |
| Fabricantes | Maxim Integrated Products | |
| Logotipo |  |
|
Hay una vista previa y un enlace de descarga de MAX5974C (archivo pdf) en la parte inferior de esta página. Total 26 Páginas | ||
|
No Preview Available !
19-5331; Rev 0; 6/10
www.DataSheet4U.com
Active-Clamped, Spread-Spectrum,
Current-Mode PWM Controllers
General Description
The MAX5974_ provide control for wide-input-voltage,
active-clamped, current-mode PWM, forward converters
in Power-over-Ethernet (PoE) powered device (PD) appli-
cations. The MAX5974A/MAX5974C are well-suited for
universal or telecom input range, while the MAX5974B/
MAX5974D also accommodate low input voltage down
to 10.5V.
The devices include several features to enhance supply
efficiency. The AUX driver recycles magnetizing cur-
rent instead of wasting it in a dissipative clamp circuit.
Programmable dead time between the AUX and main
driver allows for zero-voltage switching (ZVS). Under light-
load conditions, the devices reduce the switching fre-
quency (frequency foldback) to reduce switching losses.
The MAX5974A/MAX5974B feature unique circuitry to
achieve output regulation without using an optocoupler,
while the MAX5974C/MAX5974D utilize the traditional
optocoupler feedback method. An internal error amplifier
with a 1% reference is very useful in nonisolated design,
eliminating the need for an external shunt regulator.
The devices feature a unique feed-forward maximum
duty-cycle clamp that makes the maximum clamp volt-
age during transient conditions independent of the line
voltage, allowing the use of a power MOSFET with lower
breakdown voltage. The programmable frequency dither-
ing feature provides low-EMI, spread-spectrum operation.
The MAX5974_ are available in 16-pin TQFN-EP pack-
ages and are rated for operation over the -40°C to +85°C
temperature range.
Features
S Peak Current-Mode Control, Active-Clamped
Forward PWM Controller
S Regulation Without Optocoupler (MAX5974A/
MAX5974B)
S Internal 1% Error Amplifier
S 100kHz to 600kHz Programmable Q8% Switching
Frequency, Synchronization Up to 1.2MHz
S Programmable Frequency Dithering for Low-EMI,
Spread-Spectrum Operation
S Programmable Dead Time, PWM Soft-Start,
Current Slope Compensation
S Programmable Feed-Forward Maximum Duty-
Cycle Clamp, 80% Maximum Limit
S Frequency Foldback for High-Efficiency Light-
Load Operation
S Internal Bootstrap UVLO with Large Hysteresis
S 100µA (typ) Startup Supply Current
S Fast Cycle-by-Cycle Peak Current-Limit, 35ns
Typical Propagation Delay
S 115ns Current-Sense Internal Leading-Edge
Blanking
S Output Short-Circuit Protection with Hiccup Mode
S Reverse Current Limit to Prevent Transformer
Saturation Due to Reverse Current
S 3mm x 3mm, Lead-Free, 16-Pin TQFN-EP
Applications
PoE IEEE® 802.3af/at Powered Devices
High-Power PD (Beyond the 802.3af/at Standard)
Active-Clamped Forward DC-DC Converters
IP Phones
Wireless Access Nodes
Security Cameras
Ordering Information
PART
MAX5974AETE+
TOP MARK
+AHY
PIN-PACKAGE
16 TQFN-EP*
UVLO THRESHOLD (V)
20
MAX5974BETE+**
MAX5974CETE+
+AHZ
+AIA
16 TQFN-EP*
16 TQFN-EP*
10
20
MAX5974DETE+**
+AIB
16 TQFN-EP*
10
Note: All devices are specified over the -40°C to +85°C operating temperature range.
+Denotes a lead(Pb)-free/RoHS-compliant package.
*EP = Exposed pad. **Future product—Contact factory for availability.
IEEE is a registered service mark of the Institute of Electrical and Electronics Engineers, Inc.
FEEDBACK MODE
Sample/Hold
Sample/Hold
Continuously Connected
Continuously Connected
________________________________________________________________ Maxim Integrated Products 1
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
1 page  
www.DataSheet4U.com
Active-Clamped, Spread-Spectrum,
Current-Mode PWM Controllers
ELECTRICAL CHARACTERISTICS (continued)
(VIN = 12V (for MAX5974A/MAX5974C, bring VIN up to 21V for startup), VCS = VCSSC = VDITHER/SYNC = VFB = VFFB = VDCLMP =
VGND, VEN = +2V, NDRV = AUXDRV = SS = COMP = unconnected, RRT = 34.8kI, RDT = 25kI, CIN = 1FF, TA = -40NC to +85NC,
unless otherwise noted. Typical values are at TA = +25NC.) (Note 2)
PARAMETER
ERROR AMPLIFIER
SYMBOL
CONDITIONS
MIN TYP MAX UNITS
FB Reference Voltage
VREF
VFB when ICOMP = 0,
VCOMP = 2.5V
MAX5974A/
MAX5974B
MAX5974C/
MAX5974D
1.5
1.202
1.52
1.215
1.54
1.227
V
FB Input Bias Current
IFB VFB = 0 to 1.75V
MAX5974A/
MAX5974B
MAX5974C/
MAX5974D
-250
-500
+250
+100
nA
Voltage Gain
Transconductance
AEAMP
gM
80
MAX5974A/
MAX5974B
1.8
2.55
3.2
MAX5974C/
MAX5974D
1.8
2.66
3.5
dB
mS
Transconductance Bandwidth
MAX5974A/
BW
Open loop (typical gain
= 1) -3dB frequency
MAX5974B
MAX5974C/
MAX5974D
2
30
MHz
Source Current
Sink Current
FREQUENCY FOLDBACK (FFB)
VFB = 1V, VCOMP = 2.5V
VFB = 1.75V, VCOMP = 1V
300 375 455
300 375 455
FA
FA
VCSAVG-to-FFB Comparator
Gain
10 V/V
FFB Bias Current
IFFB
VFFB = 0V, VCS = 0V (not in FFB mode)
26
30
33
FA
NDRV Switching Frequency
During Foldback
fSW-FB
fSW/2
kHz
Note 2: All devices are 100% production tested at TA = +25NC. Limits over temperature are guaranteed by design.
Note 3: See the Output Short-Circuit Protection with Hiccup Mode section.
Note 4: The parameter is measured at the trip point of latch with VFB = 0V. Gain is defined as DVCOMP/DVCSSC for 0.15V <
DVCSSC < 0.25V.
5
5 Page 
www.DataSheet4U.com
Active-Clamped, Spread-Spectrum,
Current-Mode PWM Controllers
Pin Configuration
TOP VIEW
12 11 10 9
IN 13
EN 14
DCLMP 15
SS 16 +
MAX5974A
MAX5974B
MAX5974C
MAX5974D
EP
1234
8 CSSC
7 GND
6 FB
5 COMP
THIN QFN
Pin Description
PIN NAME
FUNCTION
Dead-Time Programming Resistor Connection. Connect resistor RDT from DT to GND to set
1 DT the desired dead time between the NDRV and AUXDRV signals. See the Dead Time section to
calculate the resistor value for a particular dead time.
Frequency Dithering Programming or Synchronization Connection. For spread-spectrum frequency
2
DITHER/
SYNC
operation, connect a capacitor from DITHER to GND and a resistor from DITHER to RT. To
synchronize the internal oscillator to the externally applied frequency, connect DITHER/SYNC to
the synchronization pulse.
Switching Frequency Programming Resistor Connection. Connect resistor RRT from RT to GND to
3 RT set the PWM switching frequency. See the Oscillator/Switching Frequency section to calculate the
resistor value for the desired oscillator frequency.
Frequency Foldback Threshold Programming Input. Connect a resistor from FFB to GND to set the
4 FFB output average current threshold below which the converter folds back the switching frequency to
1/2 of its original value. Connect to GND to disable frequency foldback.
5
COMP
Transconductance Amplifier Output and PWM Comparator Input. COMP is level shifted down and
connected to the inverting input of the PWM comparator.
11
11 Page | ||
| Páginas | Total 26 Páginas | |
| PDF Descargar | [ Datasheet MAX5974C.PDF ] | |
Hoja de datos destacado
| Número de pieza | Descripción | Fabricantes |
| MAX5974A | Current-Mode PWM Controllers | Maxim Integrated Products |
| MAX5974B | Current-Mode PWM Controllers | Maxim Integrated Products |
| MAX5974C | Current-Mode PWM Controllers | Maxim Integrated Products |
| MAX5974D | Current-Mode PWM Controllers | Maxim Integrated Products |
| Número de pieza | Descripción | Fabricantes |
| SLA6805M | High Voltage 3 phase Motor Driver IC. |
 Sanken |
| SDC1742 | 12- and 14-Bit Hybrid Synchro / Resolver-to-Digital Converters. |
 Analog Devices |
|
DataSheet.es es una pagina web que funciona como un repositorio de manuales o hoja de datos de muchos de los productos más populares, |
| DataSheet.es | 2020 | Privacy Policy | Contacto | Buscar |