參數(shù)資料
型號(hào)： BQ24630RGET
廠商： TEXAS INSTRUMENTS INC
元件分類(lèi)： 穩(wěn)壓器
英文描述： SWITCHED CAPACITOR CONVERTER, PQCC24
封裝： 4 X 4 MM, GREEN, PLASTIC, VQFN-24
文件頁(yè)數(shù)： 19/33頁(yè)
文件大?。?/td> 1893K
代理商： BQ24630RGET
top
DS(on)
G D
bottom
DS(on)
G
FOM
= R
Q
FOM
= R
Q
(
)
2
top
CHG
DS(on)
IN
CHG
on
off
S
1
P
= D
I
R
+
V
I
t
+ t
f
2
SW
on
off
on
off
Q
t
=
, t
=
I
SW
GD
GS
1
Q
= Q
+
Q
2
REG N
plt
on
off
on
off
V
I
=
, I
=
R
-
2
bottom
CHG
DS(on)
P
= (1
D)
I
R
-
ICLoss_driver
IN
g_total
s
P
V
Q
f
=
×
VREF
IN
VREF
ICLOSS
ICLOSS _ driver
VREF
Quiescent
P
(V
V
) I
P
=
-
×
=
+
SLUS894 – JANUARY 2010
www.ti.com
Figure-of-merit (FOM) is usually used for selecting proper MOSFET based on a tradeoff between the conduction
loss and switching loss. For top side MOSFET, FOM is defined as the product of a MOSFET's on-resistance,
RDS(ON), and the gate-to-drain charge, QGD. For bottom side MOSFET, FOM is defined as the product of the
MOSFET's on-resistance, RDS(ON), and the total gate charge, QG.
(17)
The lower the FOM value, the lower the total power loss. Usually lower RDS(ON) has higher cost with the same
package size.
The top-side MOSFET loss includes conduction loss and switching loss. It is a function of duty cycle
(D=VOUT/VIN), charging current (ICHARGE), MOSFET's on-resistance RDS(ON)), input voltage (VIN), switching
frequency (F), turn on time (ton) and turn off time (ttoff):
(18)
The first item represents the conduction loss. Usually MOSFET RDS(ON) increases by 50% with 100C junction
temperature rise. The second term represents the switching loss. The MOSFET turn-on and turn off times are
given by:
(19)
where Qsw is the switching charge, Ion is the turn-on gate driving current and Ioff is the turn-off gate driving
current. If the switching charge is not given in MOSFET datasheet, it can be estimated by gate-to-drain charge
(QGD) and gate-to-source charge (QGS):
(20)
Gate driving current total can be estimated by REGN voltage (VREGN), MOSFET plateau voltage (Vplt), total
turn-on gate resistance (Ron) and turn-off gate resistance Roff) of the gate driver:
(21)
The conduction loss of the bottom-side MOSFET is calculated with the following equation when it operates in
synchronous continuous conduction mode:
(22)
If the SRP-SRN voltage decreases below 5mV (The charger is also forced into non-synchronous mode when the
average SRP-SRN voltage is lower than 1.25mV), the low side FET will be turned off for the remainder of the
switching cycle to prevent negative inductor current.
As a result all the freewheeling current goes through the body-diode of the bottom-side MOSFET. The maximum
charging current in non-synchronous mode can be up to 0.9A (0.5A typ) for a 10m
Ω charging current sensing
resistor considering IC tolerance. Choose the bottom-side MOSFET with either an internal Schottky or body
diode capable of carrying the maximum non-synchronous mode charging current.
MOSFET gate driver power loss contributes to the domainant losses on controller IC, when the buck converter is
switching. Choosing the MOSFET with a small Qg_total will reduce the IC power loss to avoid thermal shut down.
(23)
Where Qg_total is the total gate charge for both upper and lower MOSFET at 6V VREGN.
The VREF load current is another component on VCC input current (Do not overload VREF) where total IC loss
can be described by following equations:
(24)
26
Copyright 2010, Texas Instruments Incorporated
Product Folder Link(s): bq24630
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
BQ24630RGET 制造商:Texas Instruments 功能描述:BATTERY CHARGER IC
BQ24640EVM 功能描述:電源管理IC開(kāi)發(fā)工具 Eval Mod for BQ24640 RoHS:否 制造商:Maxim Integrated 產(chǎn)品:Evaluation Kits 類(lèi)型:Battery Management 工具用于評(píng)估:MAX17710GB 輸入電壓: 輸出電壓:1.8 V
BQ24640RVAR 功能描述:電池管理 Hi Eff Synch Sw-Mode Batt Charge Cntrlr RoHS:否 制造商:Texas Instruments 電池類(lèi)型:Li-Ion 輸出電壓:5 V 輸出電流:4.5 A 工作電源電壓:3.9 V to 17 V 最大工作溫度:+ 85 C 最小工作溫度:- 40 C 封裝 / 箱體:VQFN-24 封裝:Reel
BQ24640RVAT 功能描述:電池管理 Hi Eff Synch Sw-Mode Batt Charge Cntrlr RoHS:否 制造商:Texas Instruments 電池類(lèi)型:Li-Ion 輸出電壓:5 V 輸出電流:4.5 A 工作電源電壓:3.9 V to 17 V 最大工作溫度:+ 85 C 最小工作溫度:- 40 C 封裝 / 箱體:VQFN-24 封裝:Reel
BQ24650EVM-639 功能描述:電源管理IC開(kāi)發(fā)工具 BQ24650 Eval Mod RoHS:否 制造商:Maxim Integrated 產(chǎn)品:Evaluation Kits 類(lèi)型:Battery Management 工具用于評(píng)估:MAX17710GB 輸入電壓: 輸出電壓:1.8 V
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