TPS5102
DUAL, HIGH-EFFICIENCY CONTROLLER FOR NOTEBOOK PC POWER
SLVS239 - SEPTEMBER 1999
D
D
D
D
D
D
D
D
D
D
D
DBT PACKAGE
(TOP VIEW)
Dual, Step-Down for Notebook System
Power
4.5 V to 25 V Input Voltage Range
Adjustable Output Voltage
95% Efficiency Achievable
PWM/Skip Mode Control Maintains High
Efficiency Under Light Load Conditions
Fixed-Frequency Operation
Resistorless Current Protection
Fixed High-Side Driver Voltage
Low Quiescent Current (0.6 mA, 2.5 V,
No switching,
Vin = 4.5 – 25 V
Iccs
Stand-by current
Both STBY < 0.5 V, Vin = 4.5 – 25 V
MIN
UNIT
oscillator
PARAMETER
fosc
Frequency
RT
fdv
Timing resistor
fdt
TEST CONDITIONS
MIN
PWM operation
56
Vcc = 4.5 V to 25 V
fosc change
VoscH
H
H level output voltage
H-level
VoscL
L
L level output voltage
L-level
kΩ
0.1%
TA = -40°C to 85°C
DC, includes internal comparator error
2%
1
Fosc = 200 kHz, Includes internal comparator error
Includes internal comparator error
1.1
1.2
1.17
0.4
Fosc = 200 kHz, Includes internal comparator error
0.5
0.6
0.43
V
V
error amp
PARAMETER
TEST CONDITIONS
Vio
Input offset voltage
Av
Open-loop voltage gain
GB
Unity-gain bandwidth
Isnk
Output sink current
Vo = 0.4 V
Isrc
Output source current
Vo = 1 V
MIN
TA = 25°C
TYP
MAX
UNIT
±2
±10
mV
50
30
dB
0.8
MHz
45
µA
300
µA
skip comparator
PARAMETER
Vhys†
Hysteresis window
Vhoff
Offset voltage
Ihbias
Bias current
TEST CONDITIONS
TLHT
Propagation delay‡ from INV to OUTxU
TLH
† Vhys is assured by design.
‡ The total delay in the table includes the driver delay.
MIN
TYP
MAX
6
9.5
13
UNIT
mV
2
mV
10
pA
TTL input signal
0.7
µs
10 mV overdrive on hysteresis band signal
1.2
µs
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TPS5102
DUAL, HIGH-EFFICIENCY CONTROLLER FOR NOTEBOOK PC POWER
SLVS239 - SEPTEMBER 1999
electrical characteristics over recommended operating free-air temperature range, VCC = 7 V
(unless otherwise noted) (continued)
driver deadtime
PARAMETER
TDRVLH
TDRVHL
TEST CONDITIONS
MIN
TYP
MAX
UNIT
Low side to high side
70
nS
High side to low side
85
nS
standby
PARAMETER
VIH
VIL
H-level input voltage
Tturnon
Tturnoff
Propagation delay
L-level input voltage
Propagation delay
TEST CONDITIONS
MIN
TYP
MAX
2.5
STBY1 STBY2
STBY1,
0.5
1.5
STBY to driver output
UNIT
V
µs
1.8
5V regulator
PARAMETER
TEST CONDITIONS
MIN
TYP
4.7
MAX
UNIT
VO
Regin
Output voltage
I = 10 mA
5.3
V
Line regulation
Vcc = 5.5 V, 25 V,
I = 10 mA
20
mV
Regl
Load regulation
I = 1 V, 10 mA,
Vcc = 5.5 V
40
mV
Ios
Short-circuit output current
Vref = 0 V
80
mA
5-V internal switch
PARAMETER
VTLH
VTHL
Threshold voltage
Vhys
Hysteresis
TEST CONDITIONS
MIN
TYP
MAX
UNIT
4.2
4.8
V
4.1
4.7
V
30
150
mV
MAX
UNIT
UVLO
PARAMETER
VTLH
VTHL
Threshold voltage
Vhys
Hysteresis
TEST CONDITIONS
MIN
TYP
3.7
4.2
V
3.6
4.1
V
10
40
150
mV
UNIT
current limit
PARAMETER
Internal current source
MIN
TYP
MAX
PWM mode
TEST CONDITIONS
10
15
20
Skip mode
3
5
7
Input offset voltage
2.5
µA
mV
driver output
PARAMETER
OUT_u sink current
OUT_d sink current
OUT_u source current
OUT_d source current
8
TEST CONDITIONS
Vo = 3 V
Vo = 3 V
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MIN
TYP
0.5
1.2
0.5
1.2
–1
–1.7
–1
–1.5
MAX
UNIT
A
A
TPS5102
DUAL, HIGH-EFFICIENCY CONTROLLER FOR NOTEBOOK PC POWER
SLVS239 - SEPTEMBER 1999
electrical characteristics over recommended operating free-air temperature range, VCC = 7 V
(unless otherwise noted) (continued)
softstart
PARAMETER
ICTRL
TEST CONDITIONS
Soft-start current
MIN
1.8
Maximum discharge current
VTLH
VTHL
TYP
MAX
2.5
3
0.92
Threshold voltage (skip mode)
UNIT
µA
mA
3.4
3.9
4.7
1.8
2.6
3.4
MIN
TYP
MAX
0.9
1.1
1.3
V
output voltage protection (COMP)
PARAMETER
TEST CONDITIONS
Threshold voltage
Progagation delay†, 50% duty cycle,
No capacitor on COMP or OUT_u pin,
Frequency = 200 kHz
UNIT
V
Turnon
900
ns
Turnoff (with channel on)
400
ns
† The delay time in the table includes the driver delay.
PWM/SKIP
PARAMETER
Threshold
Delay
TEST CONDITIONS
MIN
TYP
High to low
0.5
Low to high
2
High to low
550
Low to high
400
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UNIT
V
ns
9
TPS5102
DUAL, HIGH-EFFICIENCY CONTROLLER FOR NOTEBOOK PC POWER
SLVS239 - SEPTEMBER 1999
TYPICAL CHARACTERISTICS
QUIESCENT CURRENT (BOTH CHANNELS ON)
vs
INPUT VOLTAGE
QUIESCENT CURRENT (BOTH CHANNELS STANDBY)
vs
INPUT VOLTAGE
800
160
TJ = 125°C
140
IOff – Quiescent Current – nA
IQ – Quiescent Current –µ A
700
600
500
TJ = 25°C
TJ = -40°C
400
300
200
100
120
100
TJ = 125°C
80
60
40
TJ = -40°C
TJ = 25°C
20
0
0
10
20
VCC - Supply Voltage - V
0
30
20
7
10
15
VCC - Supply Voltage - V
4.5
Figure 1
Figure 2
DRIVE CURRENT (SOURCE)
vs
DRIVE VOLTAGE
DRIVE CURRENT (SINK)
vs
DRIVE VOLTAGE
3.5
3
5
TJ = -40°C
4
TJ = 25°C
TJ = 125°C
3
2
1
0
0.1
0.5
1
I(src) - Driver Source Current - A
V(snk) – Driver Output Voltage – V
V(src) – Driver Output Voltage – V
6
2.5
TJ = 125°C
2
TJ = 25°C
1.5
1
TJ = -40°C
0.5
0
0.1
Figure 3
10
1
0.5
I(snk) - Driver Sink Current - A
Figure 4
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25
TPS5102
DUAL, HIGH-EFFICIENCY CONTROLLER FOR NOTEBOOK PC POWER
SLVS239 - SEPTEMBER 1999
TYPICAL CHARACTERISTICS
CURRENT PROTECTION SOURCE CURRENT
(SKIP MODE)
vs
INPUT VOLTAGE
CURRENT PROTECTION SOURCE CURRENT
(PWM MODE)
vs
INPUT VOLTAGE
14
5.2
13.8
5
I (trip) – Source Current – µ A
I (protec)– Source Current – µ A
TJ = 125°C
TJ = 125°C
5.1
4.9
4.8
4.7
4.6
TJ = 25°C
4.5
13.6
TJ = 25°C
13.4
13.2
TJ = -40°C
13
TJ = -40°C
4.4
12.8
4.3
12.6
4.2
0
20
10
VCC - Supply Voltage - V
4.5
30
7
10
15
20
VCC - Supply Voltage - V
Figure 6
Figure 5
PWM/SKIP THRESHOLD VOLTAGE
vs
INPUT VOLTAGE
1
Vref5 VOLTAGE
vs
CURRENT
5.1
TJ = -40°C
0.9
TJ = 25°C
0.7
TJ = 125°C
V ref5 – Voltage – V
V T – Threshold Voltage – V
TJ = 125°C
5
0.8
25
0.6
0.5
0.4
0.3
0.2
4.9
TJ = 25°C
4.8
TJ = -40°C
4.7
4.6
0.1
0
0
10
20
VI - Supply Voltage - V
30
4.5
0
Figure 7
–10
–20
–30
Ir - Current - mA
–40
–50
Figure 8
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TPS5102
DUAL, HIGH-EFFICIENCY CONTROLLER FOR NOTEBOOK PC POWER
SLVS239 - SEPTEMBER 1999
TYPICAL CHARACTERISTICS
SOFT START CHARGE CURRENT
vs
JUNCTION TEMPERATURE
MAXIMUM OUTPUT VOLTAGE
vs
SWITCHING FREQUENCY
–3
2.5
–2.5
Soft Start Charge Current
Maximum Output Voltage
2
1.5
1
0.5
–2
–1.5
–1
–0.5
0
0
1
100
10
–40
1000
Switching Frequency – kHz
Figure 9
–20
0
25
50
70
95
TJ - Junction Temperature - °C
Figure 10
SWITCHING FREQUENCY
vs
TIMING RESISTOR
1000
Switching Frequency
Ct = 47 pF
100
Ct = 100 pF
Ct = 150 pF
Ct = 220 pF
Ct = 330 pF
10
10
100
Timing Resistor - kΩ
Figure 11
12
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1000
125
TPS5102
DUAL, HIGH-EFFICIENCY CONTROLLER FOR NOTEBOOK PC POWER
SLVS239 - SEPTEMBER 1999
TYPICAL CHARACTERISTICS
timing diagram
1.17 V Typ.
Err. Amplifier Output
0.43 V Typ.
High
Oscillator Output
Delay
OUTx_u
(100 nS Typ.)
Delay
Low
Duty
High
OUTx_d
Low
(100 nS Typ.)
Detected Over Current
Over-Current
Protection
High
Low
Current Limit
Inductor Current
IL = 0
TRIPx Voltage
LLx Voltage
GND
-Vf
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TPS5102
DUAL, HIGH-EFFICIENCY CONTROLLER FOR NOTEBOOK PC POWER
SLVS239 - SEPTEMBER 1999
APPLICATION INFORMATION
The design shown in this application report is a reference design for notebook applications. An evaluation
module (EVM), TPS5102EVM-135 (SLVP135), is available for customer testing and evaluation. The intent is
to allow a customer to fully evaluate the given design using the plug-in EVM supply shown here. For subsequent
customer board revisions, the EVM design can be copied onto the users’ PCB to shorten design cycle.
The following key design procedures will aid in the design of the notebook power supply using the TPS5102:
TP27
C6
R3
R5
SLVP135 EVM
Q1
TP26
R17
R4
L1
TP1
TP24
TP2
TP23
D1 C4
J5
TP21
R18
TP8
TP20
R19
TP9
TP19
TP6
TP7
C11
R10
R11
C19
J6
J15
J16
R21
TP10
C1
J7
J8
GND
J9
J10
GND
J11
TP11
R12
C12
TP12
C13
TP13
J12
TP18
C5
C15
D2
C21
TP14
Q4
TP17
TP15
TP16 D4
R13
C14
C20
Vo1
Vo1
Vo1GND
Vo1GND
Vin
Vin
Input GND
Input GND
Vo2GND
Vo2GND
Vo2
Vo2
RS2
C3
TP25
R14
J14
RS1
R2
L2
R20
R15
+
J13
C23
+
JP2
J4
C18
TP5
R9
J3
C22
TP22
TP4
C10
J2
+
C9
J1
Q2
C17
TP3
R8
R1
D3
+
C7
JP1
C2
+
C8
R6
Q3
TP28
R16 C16
Vin
Iin
Vo1
Io1
Vo2
6 V to 15 V
6 A
3.3 V
4 A
5 V
4 A
3.3 V
2.5 A
5V
2.5 A
16 V to 25 V
Io2
output voltage setpoint calculation
The output voltage is set by the reference voltage and the voltage divider. In the TPS5102, the reference voltage
is 1.185-V, and the divider is composed of two resistors in the EVM design that are R4 and R5, or R14 and R15.
The equation for the setpoint is:
R2
1
Vr
+ RVo–Vr
Where R1 is the top resistor (kΩ) ( R4 or R15); R2 is the bottom resistor (kΩ) ( R5 or R14); Vo is the required
output voltage (V); Vr is the reference voltage (1.185 V in TPS5102).
Example: R1 = 1 kΩ; Vr = 1.185 V; Vo = 3.3 V, then R2 = 560 Ω.
Some of the most popular output voltage setpoints are calculated in the table below:
VO
14
1.3 V
1.5 V
1.8 V
2.5 V
3.3 V
5V
R1 (top) (kΩ)
1V
1V
1V
1V
1V
1V
R2 (bottom) (kΩ)
10 V
3.7 V
1.9 V
0.9 V
0.56 V
0.31 V
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TPS5102
DUAL, HIGH-EFFICIENCY CONTROLLER FOR NOTEBOOK PC POWER
SLVS239 - SEPTEMBER 1999
APPLICATION INFORMATION
output voltage setpoint calculation (continued)
If a higher precision resistor is used, the voltage setup can be more accurate.
In some applications, the output voltage is required to be lower than the reference voltage. With a few extra
components, the lower voltage can be easily achieved. The drawing below shows the method.
VCC
VO
R(top)
Rz1
INV
Rz2
TPS5102
R(bottom)
Zener
In the schematic, the Rz1, the Rz2, and the zener are the extra components. Rz1 is used to give the zener
enough current to build up the zener voltage. The zener voltage is added to INV through Rz2. Therefore, the
voltage on the INV is still equal to the IC internal voltage (1.185 V) even if the output voltage is regulated at a
lower setpoint. The equation for setting up the output voltage is shown below:
( Vz – Vr )
Rz 2 = ( Vr –Vo)
Vr
Rtop + Rbtm
When Rz2 is the adjusting resistor for low output voltage; Vz is the zener voltage; Vr is the internal reference
voltage; Rtop is the resistor of the voltage sensing network; Rbtm is the bottom resistor of the sensing
network;VO is the required output voltage setpoint.
Example: Assuming the required output voltage setpoint is VO = 0.8 V, VZ = 5 V; Rtop = 1 kΩ; Rbottom = 1 kΩ,
Then the Rz2 = 2.43 kΩ.
output inductor ripple current
The output inductor current ripple can affect not only the efficiency, but also the output voltage ripple. The
equation is exhibited below:
Iripple
+ Vin * Vout * Iout
Lout
(Rdson
)R )
L
D
Ts
Where Iripple is the peak-to-peak ripple current (A) through the inductor; Vin is the input voltage (V); Vout is the
output voltage (V); Iout is the output current; Rdson is the on-time resistance of MOSFET (Ω); D is the duty cycle;
and Ts is the switching cycle (S). From the equation, it can be seen that the current ripple can be adjusted by
changing the output inductor value.
Example: Vin = 5 V; Vout = 1.8 V; Iout = 5 A; Rdson = 10 mΩ; RL = 5 mΩ; D = 0.36; Ts = 10 µS; Lout = 6 µH
Then, the ripple Iripple = 2 A.
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TPS5102
DUAL, HIGH-EFFICIENCY CONTROLLER FOR NOTEBOOK PC POWER
SLVS239 - SEPTEMBER 1999
APPLICATION INFORMATION
output capacitor RMS current
Assuming the inductor ripple current totally goes through the output capacitor to ground, the RMS current in the
output capacitor can be calculated as:
Iorms
+ ǸD12I
Where Io(rms) is the maximum RMS current in the output capacitor (A); ∆I is the peak-to-peak inductor ripple
current (A).
Example: ∆I = 2 A, so Io(rms) = 0.58 A
input capacitor RMS current
Assuming the input ripple current totally goes into the input capacitor to the power ground, the RMS current in
the input capacitor can be calculated as:
Iirms
+
Ǹ
Io 2
D
(1–D)
) 121 D
Iripple 2
Where Ii(rms) is the input RMS current in the input capacitor (A); Io is the output current (A); Iripple is the
peak-to-peak output inductor ripple current; D is the duty cycle. From the equation, it can be seen that the
highest input RMS current usually occurs at the lowest input voltage, so it is the worst case design for input
capacitor ripple current.
Example: Io = 5 A; D = 0.36; Iripple = 2 A,
Then, Ii(rms) = 2.42 A
soft-start
The soft-start timing can be adjusted by selecting the soft-start capacitor value. The equation is
C soft
+2
T soft
Where Csoft is the soft-start capacitance (µF) (C9 or C13 in EVM design); Tsoft is the start-up time (S).
Example: Tsoft = 5 mS, so Csoft = 0.01 µF.
16
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TPS5102
DUAL, HIGH-EFFICIENCY CONTROLLER FOR NOTEBOOK PC POWER
SLVS239 - SEPTEMBER 1999
APPLICATION INFORMATION
current protection
The current limit in TPS5102 on each channel is set using an internal current source and an external resistor
(R18 or R19). The sensed high side MOSFET drain-to-source voltage drop is compared to the set point, if the
voltage drop exceeds the limit, the internal oscillator is activated, and it continuously reset the current limit until
the over-current condition is removed. The equation below should be used for calculating the external resistor
value for current protection setpoint:
Rcl
+ Rds(on)
In skip mode,
Rcl
+ Rds(on)
)
ń
)
ń
(Itrip Iind(p-p) 2)
0.000015
(Itrip Iind(p-p) 2)
0.000005
Where Rcl is the external current limit resistor (R10 or R11); Rds(on) is the high side MOSFET (Q1 or Q3)
on-time resistance. Itrip is the required current limit; Iind(p-p) is the peak-to-peak output inductor current.
Example for voltage mode: Rds(on) = 10 mΩ, Itrip = 5 A, Iind = 2 A, so Rcl = 4 kΩ.
loop-gain compensation
Voltage mode control is used in this controller for the output voltage regulation. To achieve fast, stabilized
control, two parts are discussed in this section: the power stage small signal modeling and the compensation
circuit design.
For the buck converter, the small signal modeling circuit is shown below:
a
ZL
∧
d
Vap
D
+
ia
VO
C
∧
Ic d
VI
L
ic
D
1
+
RL
c
R
ZRC
RC
p
From this equivalent circuit, several control transfer functions can be derived: input-to-output, output
impedance, and control-to-output. Typically the control-to-output transfer function is used for the feedback
control design.
Assuming Rc and RL are much smaller than R, the simplified small signal control-to-output transfer function is:
Vod
∧
Vo
∧
d
+ +
1
ƪ
)s C
) sCRc)
ǒRc ) RLǓ ) RL ) s LC
(1
ƫ
2
Where C is the output capacitance; Rc is the equivalent serial resistance (ESR) in the output capacitor; L is the
output inductor; RL is the equivalent serial resistance (DCR) in the output inductor; R is the load resistance.
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TPS5102
DUAL, HIGH-EFFICIENCY CONTROLLER FOR NOTEBOOK PC POWER
SLVS239 - SEPTEMBER 1999
APPLICATION INFORMATION
loop-gain compensation (continued)
To achieve fast transient response and the better output voltage regulation, a compensation circuit is added to
improve the feedback control. The whole system is shown:
Power
Stage
PWM
Vref
Compensation
The typical compensation circuit used as an option in the EVM design is a part of the output feedback circuit.
The circuitry is displayed below:
R1
R2
R4
C3
C1
_
R3
C2
To PWM
+
Vref
This circuit is composed of one integrator, two poles, and two zeros:
Assuming R1
