– Fixed Frequency PWM
– Hysteretic (User Selctable)
– Light Load:
– Skip Mode
D
4.5 V to 25 V Input Voltage Range
D
Adjustable Output Voltage Down to 1.2 V
D
95% Efficiency
D
Stand-By Control
D
Over Current Protection
D
UVLO for Internal 5 V Regulation
D
Low Standby Current . . . 0.5 mA Typical
D
TA =–40°C to 85°C
description
TPS5103
MULTIPLE MODE SYNCHRONOUS DC/DC CONTROLLER
SLVS240 – SEPTEMBER 1999
DB PACKAGE
(TOP VIEW)
1
20
SOFTSTART
INV
FB
C
R
GND
REF
COMP
PWMSKIP
STBY
2
3
4
T
5
T
6
7
8
9
10
LH
19
OUT_u
18
LL
17
OUT_d
16
OUTGND
15
TRIP
14
VCC_SENSE
13
VCC
12
VREF5
11
VREG5V_IN
The TPS5103 is a synchronous buck dc/dc controller, designed for notebook PC system power . The controller
has three user-selectable operation modes available; hysteretic mode, fixed frequency PWM control, or SKIP
control.
In high current applications, where fast transient response is advantageous for reducing bulk capacitance, the
hysteretic mode is selected by connecting the Rt pin to Vref5. Selecting the PWM/SKIP modes for less
demanding transient applications is ideal for conserving notebook battery life under light load conditions. The
device includes high-side and low-side MOSFET drivers capable of driving low Rds (on) N–channel MOSFET s.
The user-selectable overcurrent protection (OCP) threshold is set by an external TRIP pin resister in order to
protect the system. The TPS5103 is configured so that a current sense resistor is not required, improving the
operating efficiency.
L1
C4
C5
OUTPUT
+
R2
C1
C2
R1
1
2
3
4
5
6
7
8
9
10
TPS5103
SOFTSTART
INV
FB
CT
RT
GND
REF
COMP
PWM/SKIP
STBY
U1
OUTU
OUTD
OUTGND
VCCSENSE
VREF5
VREG5V_IN
LH
LL
TRIP
VCC
5 V
D1
20
19
18
17
16
15
14
13
12
11
C3
R3
R4
Q1
Q2
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of
Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
TI is a trademark of Texas Instruments Incorporated.
PRODUCT PREVIEW information concerns products in the formative or
design phase of development. Characteristic data and other
specifications are design goals. Texas Instruments reserves the right to
change or discontinue these products without notice.
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
Figure 1. Typical Design
Copyright 1999, Texas Instruments Incorporated
1
TPS5103
T
°C
MULTIPLE MODE SYNCHRONOUS DC/DC CONTROLLER
SLVS240 – SEPTEMBER 1999
functional block diagram
SOFT START
FB
INV
PWMSKIP
C
R
Comp
T
T
1.185 V
Soft Start
1.185 V
_
+
_
+
Error Amp
PWM Comp.
_
+
One Shot ON
_
+
OSC
_
+
Disable
_
+
UVLO
LH
OUT_u
LL
OUT_d
OUTGND
TRIP
VCC_SENSE
VREF5
GND
V
CC
STBY
REF
1.185 V
°
–40 °C to 85
VREF
AVAILABLE OPTIONS
A
°
SSOP(DB)EVM
TPS5103IDBTPS5103EVM–136
TPS5103IDBR
PACKAGE
_
+
VREG5V_IN
2
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
I/O
DESCRIPTION
MULTIPLE MODE SYNCHRONOUS DC/DC CONTROLLER
Terminal Functions
TERMINAL
NAMENO.
COMP8IComparator input for voltage monitor
C
T
FB3OFeedback output of error amp
GND6Control GND
INV2IInverting input of both error amp and hysteretic comparator
LH20I/OBootstrap. Connect 1 µF low-ESR capacitor from LH to LL.
LL18I/O
OUT_d17I/OGate-drive output for low-side power switching FET s
OUTGND16Ground for FET drivers
OUT_u19OGate-drive output for high-side power switching FET s
PWMSKIP9I
REF7O1.185-V reference voltage output
R
T
SOFTSTAR T1IExternal capacitor from SOFTST ART to GND for soft start control
STBY10IStandby control
TRIP15IExternal resistor connection for output current control
V
CC
VCC_SENSE14ISupply voltage sense for current protection
VREF512O5-V-internal regulator output
VREG5V_IN11IExternal 5-V input (input voltage range = 4.5 V to 25 V)
4I/O
5I/OExternal resistor connection for adjusting the triangle oscillator.
13ISupply voltage input
External capacitor from CT to GND for adjusting the triangle oscillator and decreasing the current limiting
voltage
Bootstrap low. High side gate driving return and output current protection. Connect to the junction of the high
side and low side FETs for floating drive configuration.
The reference voltage is used for the output voltage setting and the voltage protection(COMP). The tolerance
is 1.5% typically.
VREF5
An internal linear voltage regulator is used for the high-side driver bootstrap voltage. Since the input voltage
range is from 4.5 V to 25 V, this voltage offers a fixed voltage for the bootstrap voltage so that the design for
the bootstrap is much easier. The tolerance is 6%.
hysteretic comparator
The hysteretic comparator is used to regulate the output voltage of the synchronous-buck converter. The
hysteresis is set internally and is typically 9.7 mV. The total delay time from the comparator input to the driver
output is typically 400 ns for going both high and low.
error amplifier
The error amplifier is used to sense the output voltage of the synchronous buck converter. The negative input
of the error amplifier is connected to the Vref voltage(1.185 V) with a resistive divider network. The output of
the error amplifier is brought out to the FB terminal to be used for loop gain compensation.
low-side driver
The low-side driver is designed to drive low-Rds(on) n-channel MOSFETs. The maximum drive voltage is 5 V
from VREF5. The current rating of driver is typically 1.2 A at sink current, –1.5 A at source current.
high-side driver
The high-side driver is designed to drive low-Rds(on) n-channel MOSFETs. The current rating of the driver is
1.2 A at sink current, –1.7 A at source current. When configured as a floating driver, the bias voltage to the driver
is developed from the VREF5, limiting the maximum drive voltage between OUT_u and LL to 5 V . The maximum
voltage that can be applied between LH and OUTGND is 30 V.
driver deadtime control
The deadtime control prevents shoot-through current from flowing through the main power FETs. During
switching transitions the
deadtime from the low-side-driver-off to the high-side-driver-on is 90 ns, and 110 ns from high-side-driver-off
to low-side-driver-on.
COMP
COMP is designed for use with a regulation output monitor. COMP also functions as an internal comparator
used for any voltage protection such as the input under voltage protection. If the input voltage is lower than the
setpoint, the comparator turns off and prevents external parts from damage. The investing terminal of the
comparator is internally connected to REF(1.185 V).
current protection
Current protection is achieved by sensing the high-side power MOSFET drain-to-source voltage drop during
on-time through VCC_SENSE and LL terminals. An external resistor between Vin and TRIP terminal with the
internal current source connected to the current comparator negative input adjusts the current limit. The typical
internal current source value is 15 µA in PWM mode, 5 µA in SKIP mode. When the voltage on the positive
terminal is lower than the negative terminal, the current comparator turns on the trigger, and then activates the
oscillator. This oscillator repeatedly reset the trigger until the over current condition is removed. The capacitor
on the C
terminal can be open or added to adjust the reset frequency.
T
deadtime control actively controls the turnon time of the MOSFET drivers. The typical
4
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
MULTIPLE MODE SYNCHRONOUS DC/DC CONTROLLER
SLVS240 – SEPTEMBER 1999
detailed description (continued)
softstart
SOFTST ART sets the sequencing of the output for any possibility. The capacitor value for a start-up time can
be calculated by the following equation: C = 2xT (uF) where C is the external capacitor value, T is the required
start-up time in (ms).
standby
This controller can be switched into standby mode by grounding the STBY terminal. When it is in standby mode,
the quiescent current is less than 1.0 uA.
UVLO
The under-voltage-lock-out (ULVO) threshold is approximately 3.8 V. The typical hysteresis is 55 mV.
5-V Switch
5-V Switch if the internal 5-V switch senses a 5-V input from REG5V terminal, the internal 5-V linear regulator
will be disconnected from the MOSFET drivers. The external 5 V will be used for both the low-side driver and
the high-side bootstrap, thus increasing the efficiency.
PWM/SKIP switch
TPS5103
The PWM/SKIP switch selects the output operating mode. This controller has three operational modes, PWM,
SKIP, and Hysteretic. The PWM and SKIP mode control should be used for slower transient applications.
oscillator
The oscillator gives a triangle wave by connecting an external resistor to the R
terminal and an external
T
capacitor to the CT terminal. The voltage amplitude is 0.43 V ~ 1.17 V. This wave is connected to the noninverting input of the PWM comparator.
Comparison Table Between PWM Mode and Hysteretic Mode
MODEPWMHYSTERETIC
FrequencyFixedNot Fixed
Transient ResponseNormalVery fast
Feed back compensationNeedNeedless
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
5
TPS5103
VIInput voltage
V
MULTIPLE MODE SYNCHRONOUS DC/DC CONTROLLER
SLVS240 – SEPTEMBER 1999
absolute maximum ratings over operating free-air temperature (unless otherwise noted)
Stresses beyond those listed under “absolute maximum ratings” may cause permanent damage to the device. These are stress ratings only, and
functional operation of the device at these or any other conditions beyond those indicated under “recommended operating conditions” is not
implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
NOTES: 1. All voltage values are with respect to the network ground terminal.
2. See Dissipation Rating Table for free-air temperature range above 25°C.
electrical characteristics over recommended operating free-air temperature range, VCC = 7 V
(unless otherwise noted)
reference voltage
PARAMETERTEST CONDITIONSMINTYPMAXUNIT
ref
ReginLine regulation
ReglLoad regulation
†
Not a JEDEC symbol.
†
†
TA = 25°C,I
= 50 µA
‡
I
vref
VCC = 4.5 V to 25 V,I = 50 µA0.212mV
I = 1 µA to 1 mA0.510mV
oscillator
PARAMETERTEST CONDITIONSMINTYPMAXUNIT
fFrequencyPWM mode500kHz
R
T
fdv
fdt
HL
LL
†
Not a JEDEC symbol.
‡
The output voltages of oscillator (f = 200 kHz) are ensured by design.
Timing resistor47kΩ
VCC = 4.5 V to 25 V0.1%
TA = –40°C to 85°C2%
p
p
DC includes internal comparator error11.11.2
f = 200 kHz, includes internal comparator error1.17
DC includes internal comparator error0.40.50.6
f = 200 kHz, includes internal comparator error0.43
= 50 µA1.167 1.185 1.203
vref
1.1551.215
error amp
PARAMETERTEST CONDITIONSMINTYPMAXUNIT
VInput offset voltageTA = 25°C210mV
AvOpen-loop voltage gain
GBUnity-gain bandwidth
I