TC1302A_13 Datasheet, PDF (14/26 Pages) Microchip Technology – Low Quiescent Current Dual Output LDO

TC1302A/B
6.0 APPLICATION CIRCUITS/
ISSUES
6.1 Typical Application
The TC1302A/B is used for applications that require
the integration of two LDOs.
2.8V @ 300 mA
C_OUT1
1 µF Ceramic
X5R
C_bypass
10 nF Ceramic
TC1302A
1 _NC
8
NC
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
TC1302B
1 _NC
8
SHDN1
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:
TC1302A/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
6.2 Power Calculations
6.2.1 POWER DISSIPATION
The internal power dissipation within the TC1302A/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.
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 TC1302A/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.
EQUATION 6-2:
P_{IGND} = V_{INMAX}  I_VIN
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.
The total power dissipated within the TC1302A/B is the
sum of the power dissipated in both of the LDOs and
the P(I_GND) term. Because of the CMOS construction,
the typical I_GND for the TC1302A/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 dissi-
pation and can be neglected.
The maximum continuous operating junction
temperature specified for the TC1302A/B is +125°C. To
estimate the internal junction temperature of the
TC1302A/B, the total internal power dissipation is
multiplied by the thermal resistance from junction to
ambient (R_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  R_JA + T_AMAX
T_J(MAX) = Maximum continuous junction
temperature.
P_TOTAL = Total device power dissipation.
R_JA = Thermal resistance from junction
to ambient.
T_AMAX = Maximum Ambient Temperature.
DS21333C-page 14
 2003-2012 Microchip Technology Inc.