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PDF TD1728 Data sheet ( Hoja de datos )
| Número de pieza | TD1728 | |
| Descripción | High-Performance PWM Controller | |
| Fabricantes | Techcode | |
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T echcode®
High-Performance PWM Controller
DATASHEET
TD1728
General Description
Features
The TD1728 is a single‐phase, constant‐on‐time, z Adjustable Output Voltage from +0.7V to +5.5V
synchronous PWM controller, which drives N‐channel z 0.7V Reference Voltage
MOSFETs. The TD1728 steps down high voltage to z ±1% Accuracy Over‐Temperature
generate low‐voltage chipset or RAM supplies in notebook z Operates from an Input Battery Voltage Range of +1.8V
computers.
to +32V
The TD1728 provides excellent transient response and z Power‐On‐Reset Monitoring on VCC Pin
accurate DC voltage output in either PFM or PWM Mode. In z Excellent Line and Load Transient Responses
Pulse Frequency Mode (PFM), the TD1728 provides very high z PFM Mode for Increased Light Load Efficiency
efficiency over light to heavy loads with loading‐ modulated z Selectable PWM Frequency from 4 Preset Values
switching frequencies. In PWM Mode, the converter works z Integrated MOSFET Drivers
nearly at constant frequency for low‐noise requirements.
z Integrated Bootstrap Forward P‐CH MOSFET
The TD1728 is equipped with accurate positive current‐ limit, z Adjustable Integrated Soft‐Start and Soft‐Stop
output under‐voltage, and output over‐voltage z Selectable Forced PWM or Automatic PFM/PWM Mode
protections, perfect for NB applications. The Power‐On‐ z Power Good Monitoring
Reset function monitors the voltage on VCC to prevent z 70% Under‐Voltage Protection
wrong operation during power‐on. The TD1728 has a 1ms z 125% Over‐Voltage Protection
digital soft‐start and built‐in an integrated output z Adjustable Current‐Limit Protection
discharge method for soft‐stop. An internal integrated z Using Sense Low‐Side MOSFET’s RDS(ON)
soft‐start ramps up the output voltage with programmable z Over‐Temperature Protection
slew rate to reduce the start‐up current. A soft‐stop function z TDFN‐10 3x3 Package
actively discharges the output capacitors with controlled z Lead Free and Green Devices Available (RoHS Compliant)
reverse inductor current.
The TD1728 is available in 10pin TDFN 3x3 package.
Applications
z Notebook
z Table PC
z Hand‐Held Portable
z AIO PC
z LCD Monitor / TV
z Battery Charger
z ADSL Modem
z Telecom / Networking Equipment
December, 20, 2011 Techcode Semiconductor Limited www.techcodesemi.com
1
1 page  
T echcode®
High-Performance PWM Controller
Electrical Characteristics
DATASHEET
TD1728
Refer to the typical application circuit. These specifications apply over VVCC = 12V, TA = ‐40°C to 85°C, unless otherwise noted. Typical values are at TA = 25°C.
Symbol
Parameter
Test Conditions
VOUT
VREF
IFB
TDIS
IVCC
IVCC SHDN
VOUT AND VFB VOLTAGE
Output Voltage
Adjustable output range
Reference Voltage
Regulation Accuracy
TA = 25 oC
TA = 0 oC ~ 85 oC
TA = -40 oC ~ 85 oC
FB Input Bias Current
FB = 0.7V
VOUT Discharge Time
EN low to FB = 0V
SUPPLY CURRENT
VCC Input Bias Current
VCC Shutdown Current
VCC Current, PWM, EN = 5V, VFB = 0.735V, PHASE =
0 5V
EN = GND, VCC = 5V
SWITCHING FREQUENCY AND SUTY AND INTERNAL SOFT-START
RRF = 470k , TA = 25oC, VIN=8V, VOUT=1.1V, IOUT=10A
RRF = 200k , TA = 25oC, VIN=8V, VOUT=1.1V, IOUT=10A
FSW Switching Frequency
RRF = 100k , TA = 25oC, VIN=8V, VOUT=1.1V, IOUT=10A
RRF = 39k , TA = 25oC, VIN=8V, VOUT=1.1V, IOUT=10A
TD1728
Unit
Min. Typ. Max.
0.7
- 5.5
V
- 0.7
-V
-0.5 -
+0.5 %
-0.8 -
+0.8 %
-1.0 -
+1.0 %
- 0.02 0.1
uA
- 12
- ms
- 250 520 uA
- 0 1 uA
266 290 314
312 340 368
349 380 411
395 430 465
kHz
TON(MIN) Minimum On Time
TOFF(MIN) Minimum Off Time
VFB = 0.65V, VPHASE = -0.1V, OCSET = OPEN
80 110 140
350 450 550
ns
ns
TSS Internal Soft-Start Time
UGATE Pull-Up Resistance
UGATE Sink Resistance
LGATE Pull-Up Resistance
LGATE Sink Resistance
UGATE to LGATE Dead-Time
LGATE to UGATE Dead-Time
VF Ron
IR Reverse Leakage
EN High to VOUT Regulation (95%)
GATE DRIVER
BOOT-UGATE = 0.5V
UGATE-PHASE = 0.5V
PVCC-LGATE = 0.5V
LGATE-GND = 0.5V
UGATE falling to LGATE rising
LGATE falling to UGATE rising
BOOTSTRAP SWITCH
VVCC - VBOOT-GND, IF = 10mA
VBOOT-GND = 30V, VPHASE = 25V, VVCC = 5V
0.7 1.0 1.3
ms
- 1.5
- 0.7
- 1.0
- 0.5
- 20
- 20
3
1.8
2.2
1.2
-
-
Ω
Ω
Ω
Ω
ns
ns
- 0.5 0.8
- - 0.5
V
uA
VVCC THR Rising VSS POR Threshold
VCC POR Hysteresis
EN Voltage Threshold
VCC POR THRESHOLD
Enable
Shutdown
CONTROL INPUTS
4.2 4.35 4.45
- 100
-
V
mV
1.8 - - V
-
- 0.5
V
December, 20, 2011 Techcode Semiconductor Limited www.techcodesemi.com
5
5 Page 
T echcode®
High-Performance PWM Controller
DATASHEET
TD1728
Function Description(Cont.)
switching frequency.
Under‐Voltage Protection (UVP)
In the operational process, if a short‐circuit occurs, the output voltage
will drop quickly. When load current is bigger than current‐limit
threshold value, the output voltage will fall out of the required
regulation range. The undervoltage protection circuit continually
monitors the FB voltage after soft‐start is completed. If a load step is
strong enough to pull the output voltage lower than the undervoltage
threshold, the under‐voltage threshold is 70% of the nominal output
voltage, the internal UVP delay counter starts to count. After 16μs
debounce time, the device turns off both high‐side and low‐side
MOSEFET with latched and starts a soft‐stop process to shut down the
output gradually. Toggling enable pin to low or recycling VCC,will clear
the latch and bring the chip back to operation.
During soft‐start stage before the PGOOD pin is ready,the
Over‐Voltage Protection (OVP)
The over‐voltage function monitors the output voltage by FB pin. When
under‐voltage protection is prohibited. The over‐voltage and
the FB voltage increases over 125% of the reference voltage due to the
current‐limit protection functions are enabled. If the output capacitor high‐side MOSFET failure or for other reasons, the over‐voltage
has residue voltage before start‐up, both low‐side and high‐side
protection comparator designed with a 1.5μs noise filter will force the
MOSFETs are in off‐state until the internal digital soft‐start voltage
lowside MOSFET gate driver fully turn on and latch high. This action
equals to the VFB voltage. This will ensure that the output voltage starts actively pulls down the output voltage.This OVP scheme only clamps
from its existing voltage level.In the event of under‐voltage,
the voltage overshoot and does not invert the output voltage when
over‐temperature, or shutdown, the chip enables the soft‐stop
otherwise activated with a continuously high output from low‐side
function. The soft‐stop function discharges the output voltage to the Over‐Voltage Protection (OVP) (Cont.)
GND. The duration of the discharge time is 8ms.
MOSFET driver. It’s a common problem for OVP schemes with a latch.
Power OK Indicator
Once an over‐voltage fault condition is set, it can only be reset by
The TD1728 features an open‐drain POK pin to indicate output toggling EN, VCC power‐on‐reset signal.
regulation status. In normal operation, when the output voltage rises Current‐Limit
90% of its target value, the POK goes high after 63us internal delay. The current‐limit circuit employs a “valley” current‐sensing algorithm
When the output voltage outruns 70% or 125% of the target voltage, (See Figure 2). The TD1728 uses the low‐side MOSFET’s RDS(ON) of the
POK signal will be pulled low immediately.
synchronous rectifier as a current‐sensing element. If the magnitude of
Since the FB pin is used for both feedback and monitoring purposes, the the current‐sense signal at PHASE pin is above the currentlimit
output voltage deviation can be coupled directly to the FB pin by the threshold, the PWM is not allowed to initiate a new cycle. The actual
capacitor in parallel with the voltage divider as shown in the typical peak current is greater than the currentlimit threshold by an amount
applications. In order to prevent false POK from dropping, capacitors equals to the inductor ripple current. Therefore, the exact current‐limit
need to parallel at the output to confine the voltage deviation with characteristic and maximum load capability are the functions of the
severe load step transient.
sense resistance, inductor value, and input voltage
December, 20, 2011 Techcode Semiconductor Limited www.techcodesemi.com
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11 Page | ||
| Páginas | Total 17 Páginas | |
| PDF Descargar | [ Datasheet TD1728.PDF ] | |
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