TC1301A Datasheet, PDF (17/28 Pages) Microchip Technology – Dual LDO with Microcontroller RESET Function

6.0 APPLICATION CIRCUITS/
ISSUES
6.1 Typical Application
The TC1301A/B is used for applications that require
the integration of two LDO’s and a microcontroller
RESET.
System RESET
2.8V @ 300 mA
C_OUT1
1 µF Ceramic
X5R
C_bypass
10 nF Ceramic
TC1301A
1 _{RESET VDET} 8
2 _VOUT1
3 _GND
V_IN ⁷ _1.8V
V_OUT2 ^{6 @ 150 mA}
BATTERY
C_IN
1 µF
4 _{Bypass SHDN2} 5
C_OUT2
1 µF Ceramic
X5R
2.7V
to
4.2V
ON/OFF Control V_OUT2
ON/OFF Control V_OUT1
TC1301B
System RESET
1 _{RESET SHDN1} 8
2.8V @ 300 mA 2 _VOUT1
C_OUT1
1 µF Ceramic
3 _GND
V_IN ⁷ _1.8V
V_OUT2 ^{6 @ 150 mA}
BATTERY
C_IN
1 µF
X5R
4 _BypassSHDN2 5
C_OUT2
1 µF Ceramic
X5R
2.7V
to
4.2V
ON/OFF Control V_OUT2
FIGURE 6-1:
TC1301A/B.
Typical Application Circuit
6.1.1 APPLICATION INPUT CONDITIONS
Package Type = 3X3DFN8
Input Voltage Range = 2.7V to 4.2V
V_IN maximum = 4.2V
V_IN typical = 3.6V
V_OUT1 = 300 mA maximum
V_OUT2 = 150 mA maximum
System RESET Load = 10 kΩ
6.2 Power Calculations
6.2.1 POWER DISSIPATION
The internal power dissipation within the TC1301A/B is
a function of input voltage, output voltage, output
current and quiescent current. The following equation
can be used to calculate the internal power dissipation
for each LDO.
TC1301A/B
EQUATION 6-1:
P_LDO = (V_IN(MAX)) – V_OUT(MIN)) × I_OUT(MAX))
P_LDO = LDO Pass device internal power
dissipation
V_IN(MAX) = Maximum input voltage
V_OUT(MIN)= LDO minimum output voltage
In addition to the LDO pass element power dissipation,
there is power dissipation within the TC1301A/B as a
result of quiescent or ground current. The power
dissipation as a result of the ground current can be
calculated using the following equation. The V_IN pin
quiescent current and the V_DET pin current are both
considered. The V_IN current is a result of LDO
quiescent current, while the V_DET current is a result of
the voltage detector current.
EQUATION 6-2:
P_I(GND) = V_IN(MAX) × (I_VIN + I_VDET)
P_I(GND) = Total current in ground pin.
V_IN(MAX) = Maximum input voltage.
I_VIN = Current flowing in the V_IN pin with no
output current on either LDO output.
I_VDET = Current in the V_DET pin with
RESET loaded.
The total power dissipated within the TC1301A/B is the
sum of the power dissipated in both of the LDO’s and
the P(I_GND) term. Because of the CMOS construction,
the typical I_GND for the TC1301A/B is 116 µA.
Operating at a maximum of 4.2V results in a power
dissipation of 0.5 milliWatts. For most applications, this
is small compared to the LDO pass device power
dissipation and can be neglected.
The maximum continuous operating junction
temperature specified for the TC1301A/B is 125°C. To
estimate the internal junction temperature of the
TC1301A/B, the total internal power dissipation is
multiplied by the thermal resistance from junction to
ambient (Rθ_JA) of the device. The thermal resistance
from junction to ambient for the 3X3DFN8 pin package
is estimated at 41° C/W.
EQUATION 6-3:
T_J(MAX) = P_TOTAL × Rθ_JA + T_AMAX
T_J(MAX) = Maximum continuous junction
temperature.
P_TOTAL = Total device power dissipation.
Rθ_JA = Thermal resistance from junction-to-
ambient.
T_AMAX = Maximum ambient temperature.
© 2005 Microchip Technology Inc.
DS21798B-page 17